# GCN_circulars

GRB_name: GRB150801A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18103
SUBJECT: GRB 150801A: Tiled Swift observations
DATE:    15/08/01 15:37:17 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a series of observations, tiled on the sky, of the
MAXI GRB 150801A. Automated analysis of the XRT data will
be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00047

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. The probability of finding
serendipitous sources, unrelated to the MAXI event is high: any X-ray source
considered to be a probable afterglow candidate will be reported via a GCN Circular
after manual consideration.

Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).

This circular is an official product of the Swift-XRT team.


GRB_name: GRB150801B
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18104
SUBJECT: GRB 150801B: Swift detection of a burst
DATE:    15/08/01 22:58:56 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

B. Sbarufatti (INAF-OAB/PSU), S. D. Barthelmy (GSFC),
J. R. Cummings (NASA/UMBC), L. M. Z. Hagen (PSU),
N. P. M. Kuin (UCL-MSSL), F. E. Marshall (NASA/GSFC),
D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the
Swift Team:

At 22:41:48 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150801B (trigger=650977).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 82.959, -5.387 which is 
   RA(J2000) = 05h 31m 50s
   Dec(J2000) = -05d 23' 14"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows several overlapping peaks
with a total duration of about 20 sec.  The peak count rate
was ~2600 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 22:43:07.3 UT, 78.8 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 82.9666, -5.3883 which
is equivalent to:
   RA(J2000)  = 05h 31m 51.99s
   Dec(J2000) = -05d 23' 18.0"
with an uncertainty of 2.3 arcseconds (radius, 90% containment). This
location is 27 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper. 

A power-law fit to a spectrum formed from promptly downlinked event
data does not constrain the column density. 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 83 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
The 8'x8' region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.24. 

We note that this event is in the vicinity of the Orion Nebula. 
However, it appears in all other respects to be a typical GRB. 

Burst Advocate for this burst is B. Sbarufatti (boris.sbarufatti AT brera.inaf.it). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)


GRB_name: GRB150721A
Detection_method: iPTF
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18105
SUBJECT: GRB 150721A (Fermi GBM Trigger 459150552): iPTF P48 Observations
DATE:    15/08/02 01:20:21 GMT
FROM:    S. Bradley Cenko at NASA/GSFC  <brad.cenko@nasa.gov>

S. B. Cenko, L. P. Singer (NASA/GSFC), M. M. Kasliwal (Carnegie), and V. Bhalerao (IUCAA) report on behalf of a larger collaboration:

We imaged 12 fields covering an area of 87 deg^2 in and around the 1-sigma statistical+systematic uncertainty region of the final Fermi GBM localization.  We estimate a 72% a priori probability that these fields contain the true location of the source.  Sifting through candidate variable sources using image subtraction and standard iPTF vetting procedures, we detected the following optical transient candidates:

iPTF15bud, at the coordinates:
  RA(J2000) = 22h 20m 08.68s (335.036172 deg)
  Dec(J2000) = +08d 59' 01.9" (+8.983848 deg)
The source is coincident with the nucleus of the resolved source SDSS J222008.67+085901.7 (photo-z = 0.20 +/- 0.02)
The following P48 photometry indicates no evidence for intra-night variability:
  +5.25 hr: R = 19.88 +/- 0.04
  +5.97 hr: R = 19.91 +/- 0.08

iPTF15buc, at the coordinates:
  RA(J2000) = 22h 20m 26.17s (335.109057 deg)
  Dec(J2000) = +05d 59' 31.1" (+5.991972 deg)
The source is coincident with the nucleus of the resolved source SDSS J222026.17+055930.4 (photo-z = 0.08 +/- 0.01)
The following P48 photometry indicates no evidence for intra-night variability:
  +5.09 hr: R = 19.64 +/- 0.04
  +5.83 hr: R = 19.57 +/- 0.04

iPTF15bub, at the coordinates:
  RA(J2000) = 22h 21m 17.29s (335.322031 deg)
  Dec(J2000) = +06d 52' 24.7" (+6.873532 deg)
The source is coincident with the nucleus of the resolved source SDSS J222117.28+065224.4 (photo-z = 0.32 +/- 0.07)
The following P48 photometry indicates no evidence for intra-night variability:
  +5.26 hr: R = 20.40 +/- 0.07
  +6.00 hr: R = 20.43 +/- 0.20

iPTF15bua, at the coordinates:
  RA(J2000) = 22h 00m 00.79s (330.003312 deg)
  Dec(J2000) = +11d 25' 14.0" (+11.420547 deg)
The source is coincident with the nucleus of the resolved source SDSS J220000.78+112513.9 (photo-z = 0.25 +/- 0.06)
The following P48 photometry indicates no evidence for intra-night variability:
  +5.54 hr: R = 20.94 +/- 0.12
  +5.56 hr: R = 21.22 +/- 0.20

iPTF15btz, at the coordinates:
  RA(J2000) = 21h 57m 06.00s (329.274989 deg)
  Dec(J2000) = +12d 06' 45.8" (+12.112722 deg)
The source is near the nucleus of a resolved source in SDSS.
The following P48 photometry indicates marginal evidence for fading:
  +5.01 hr: R = 20.26 +/- 0.07
  +5.56 hr: R = 20.50 +/- 0.12

Times are relative to the GBM trigger. Magnitudes are in the Mould R filter and in the AB system, calibrated with respect to point sources in SDSS as described in Ofek et al. (2012, http://dx.doi.org/10.1086/664065).

Given the likely nuclear associations and the lack of fading, we do not consider any of these sources to be likely candidates for the optical afterglow of GRB 150721A.

The diagram http://www.its.caltech.edu/~lsinger/iptf/Fermi459150552.pdf shows the locations of our candidates and the P48 fields in relation to the Fermi GBM 1- and 2-sigma statistical+systematic contours. 


GRB_name: GRB150801B
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18108
SUBJECT: GRB 150801B: Enhanced Swift-XRT position
DATE:    15/08/02 02:52:40 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 1630 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 150801B, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 82.96622, -5.38930 which is equivalent
to:

RA (J2000): 05h 31m 51.89s
Dec (J2000): -05d 23' 21.5"

with an uncertainty of 1.7 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.


GRB_name: GRB150801B
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18109
SUBJECT: GRB 150801B: Swift-XRT refined Analysis
DATE:    15/08/02 18:14:27 GMT
FROM:    Boris Sbarufatti at INAF-OAB/IASFPA  <boris.sbarufatti@brera.inaf.it>

P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), T.G.R. Roegiers (PSU), L.M.
McCauley (PSU), J.A. Kennea (PSU), B.P. Gompertz (U. Leicester), J.P.
Osborne (U. Leicester), A. D'ai (INAF-IASFPA) and B. Sbarufatti
(INAF-OAB/PSU) report on behalf of the Swift-XRT team:

We have analysed 12 ks of XRT data for GRB 150801B (Sbarufatti et al.
GCN Circ. 18104), from 64 s to 40.0 ks after the BAT trigger. We have
analysed 12 ks of XRT data for GRB 150801B (Sbarufatti et al. GCN Circ.
18104), from 64 s to 40.0 ks after the BAT trigger. The data comprise
8 s in Windowed Timing (WT) mode while Swift was slewing to the burst,
270 s in PC mode, a further 185 s in WT mode during a bright flare
starting at T0+366 s (also seen in the BAT), with the remainder 11.5 ks
in Photon Counting (PC) mode. The enhanced XRT position for this burst
was given by Evans et al. (GCN Circ. 18108).

The late-time light curve (from T0+4.9 ks) can be modelled with a
power-law decay with a decay index of alpha=1.74 (+0.18, -0.17).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.79 (+0.21, -0.19). The
best-fitting absorption column is  3.0 (+/-0.4) x 10^22 cm^-2, in
excess of the Galactic value of 2.7 x 10^21 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 7.6 x 10^-11 (1.5 x 10^-10) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      3.0 (+/-0.4) x 10^22 cm^-2
Galactic foreground: 2.7 x 10^21 cm^-2
Excess significance: 10.8 sigma
Photon index:      1.79 (+0.21, -0.19)

If the light curve continues to decay with a power-law decay index of
1.74, the count rate at T+24 hours will be 1.4 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.1 x
10^-13 (2.2 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00650977.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB150801B
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18110
SUBJECT: GRB 150801B: Swift-BAT refined analysis
DATE:    15/08/02 19:47:20 GMT
FROM:    Jay R. Cummings at NASA/GSFC/Swift  <james.r.cummings@nasa.gov>

S. D. Barthelmy (GSFC),  J. R. Cummings (CPI), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU),
T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
  
Using the data set from T-240 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 150801B (trigger #650977) (Sbarufatti,
et al., GCN Circ. 18104).  The BAT ground-calculated position is
RA, Dec = 82.961, -5.374 deg which is
    RA(J2000)  =  05h 31m 50.7s
    Dec(J2000) = -05d 22' 28.0"
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 62%.
  
The mask-weighted light curve shows two widely separated episodes.  The first
episode was about 40 seconds long starting at about T-20 seconds.  There were two
prominent overlapping FRED peaks at T0 and T+10 seconds, followed by a return to
background level.  The second episode became detectable in BAT at about T+330
seconds and returned to background about T+450 seconds.  There were two smaller
cusp-shaped peaks at T+370 and T+390 seconds, about 10 and 7 seconds long.  The
peaks between 330 and 450 seconds are at the same time as bright X-ray flares
detected by XRT.  T90 (15-350 keV) was 426 +- 30 sec (estimated error including
systematics).
  
The time-averaged spectrum from T-30.16 to T+433.94 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.84 +- 0.14.  The fluence in the 15-150 keV band is 3.1 +- 0.2 x 10^-06 erg/cm2.
The 1-sec peak photon flux measured from T+9.32 sec in the 15-150 keV band
is 2.5 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.
  
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/650977/BA/


GRB_name: GRB150801B
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18111
SUBJECT: GRB 150801B: Swift/UVOT Upper Limits
DATE:    15/08/02 22:58:24 GMT
FROM:    Lea Hagen at PSU  <lea.zernow.hagen@gmail.com>

L. M. Z. Hagen (PSU) and B. Sbarufatti (INAF-OAB/PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150801B
84 s after the BAT trigger (Sbarufatti et al., GCN Circ. 18104).
No optical afterglow consistent with the XRT position (Evans et al.,
GCN Circ. 18108) is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC            83          233          147         >20.17
white              575        12513         1345         >21.35
v                  625        16812          901         >19.63
b                  551        11601         1264         >20.68
u_FC               295          545          245         >19.42
u                  699         7399          490         >19.53
uvw1              1105         7194          432         >19.41
uvw2              4943        13218          884         >19.89

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.24 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB150801A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18112
SUBJECT: GRB 150801A: Swift-XRT observations
DATE:    15/08/03 17:53:41 GMT
FROM:    Boris Sbarufatti at INAF-OAB/IASFPA  <boris.sbarufatti@brera.inaf.it>

A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), D.N.
Burrows (PSU), T.G.R. Roegiers (PSU), L.M. McCauley (PSU), A.P.
Beardmore (U. Leicester), B.P. Gompertz (U. Leicester) and P.A. Evans
(U. Leicester) report on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the MAXI-detected
burst GRB 150801A (Ishikawa et al. GCN Circ. 18102) in a series of
observations tiled on the sky. The total exposure time is 3.8 ks,
distributed over 4 tiles; the maximum exposure at a single sky location
was 1.6 ks. The data were collected between T0+50.8 ks and T0+62.9 ks,
and are entirely in Photon Counting (PC) mode. 

No X-ray sources have been detected. The 3-sigma upper limit in the
field (not including the regions where the tiles overlap) ranges from
~0.006 to ~0.009 ct s^-1, corresponding to a 0.3-10 keV observed flux
of 2.4e-13 to 3.8e-13 erg cm^-2 s^-1 (assuming a typical GRB spectrum).

The results of the XRT-team automatic analysis of the tiled XRT
observations, including a position-specific upper limit calculator, are
available at http://www.swift.ac.uk/xrt_products/TILED_GRB00047.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB150727A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18113
SUBJECT: GRB 150727A: IRSF NIR observation
DATE:    15/08/04 08:45:32 GMT
FROM:    Daisuke Kuroda at OAO/NAOJ  <dikuroda@oao.nao.ac.jp>

K. L. Murata (Nagoya U.), T. Kusune (Nagoya City U.), H. Onozato (Tohoku U.) and T. Nagayama (Kagoshima U.)

We observed the field of GRB 150727A (Cenko et al., GCN Circular #18076) with the near-infrared (J, H, Ks) simultaneous imaging polarimeter SIRPOL attached to 1.4 m telescope IRSF (InfraRed Survey Facility) in Sutherland observatory, South Africa.

The observations started on 2015-07-27 19:25:30 UT (~ 9 min. after the burst).
We detected an uncatalogued source within 5 arcsec from the Swift/UVOT preliminary position reported in the GCN circular of Breeveld et al. (GCN Circular #18084).
We have obtained the following preliminary magnitude (Vega magnitude system):

J   = 18.9 +- 0.2
H   = 18.1 +- 0.1
Ks  = 17.1 +- 0.2

Given magnitudes were calibrated against 2MASS point sources in this field.

This observation was carried out by IRSF and OISTER collaboration.


GRB_name: GRB150728A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18115
SUBJECT: GRB 150728A: TNG optical observations
DATE:    15/08/05 20:10:52 GMT
FROM:    Paolo D'Avanzo at INAF-OAB  <paolo.davanzo@brera.inaf.it>

P. D'Avanzo, D. Fugazza (INAF/OABr), V. D'Elia (INAF/OAR and ASI/ASDC), V. Lorenzi, H. Stoev (INAF/TNG) report on behalf of the CIBO collaboration:
We observed the field of the short GRB 150728A (Krimm et al., GCN 18087; Ukwatta et al. GCN 18091) with the 3.6m TNG telescope equipped with the DOLoRes camera. Observations consisted of 12 images in the r-sdss band for a total of 48 min exposure. The seeing was ~1.2".

No object is detected within the enhanced XRT position (Beardmore et al., GCN 18088), down to a limiting magnitude r > 24.5 (calibrated against nearby USNO-B1 stars). The mean time of the observation was 2015 Jul 30.9439 UT (2.41 days after the GRB). In particular, we find no evidence for fading for the object reported by Dichiara et al. in GCN 18090 (which appears to be point-like in our images), by measuring in our dataset a magnitute of r = 21.4 +/- 0.1 for this source (calibrated against nearby USNO-B1 stars). 


GRB_name: GRB150811A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18119
SUBJECT: GRB 150811A: Swift detection of a burst
DATE:    15/08/11 04:21:01 GMT
FROM:    Kim Page at U.of Leicester  <klp5@leicester.ac.uk>

P. A. Evans (U Leicester), A. Y. Lien (GSFC/UMBC) and
K. L. Page (U Leicester) report on behalf of the Swift Team:

At 04:06:09 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150811A (trigger=651882).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 291.371, -15.438 which is 
   RA(J2000) = 19h 25m 29s
   Dec(J2000) = -15d 26' 16"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a weak complex
peak structure with a duration of about 20 sec.  The peak count rate
was ~1000 counts/sec (15-350 keV), at ~3 sec after the trigger. 

The XRT began observing the field at 04:08:30.6 UT, 141.6 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 291.33917, -15.42535 which
is equivalent to:
   RA(J2000)  = 19h 25m 21.40s
   Dec(J2000) = -15d 25' 31.3"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 119 arcseconds from the BAT onboard position, within the
BAT error circle. This position may be improved as more data are
received; the latest position is available at
http://www.swift.ac.uk/sper.  We cannot determine whether the source is
fading at the present time. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 1.54
x 10^21 cm^-2 (Willingale et al. 2013). 

The initial flux in the 2.5 s image was 4.59e-10 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 147 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
The 8'x8' region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.17. 

Burst Advocate for this burst is P. A. Evans (pae9 AT star.le.ac.uk). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)


GRB_name: GRB150811A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18120
SUBJECT: GRB 150811A: RATIR Optical Afterglow Detection
DATE:    15/08/11 04:49:37 GMT
FROM:    Nat Butler at Az State U  <natbutler@asu.edu>

Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William
H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB),
J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara
(ORAU/GSFC), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico
Ramirez-Ruiz (UCSC), JosÃ© A. de Diego (UNAM), Leonid Georgiev (UNAM), JesÃºs
GonzÃ¡lez (UNAM), Carlos RomÃ¡n-ZÃºÃ±iga (UNAM), Neil Gehrels (GSFC), and
Harvey Moseley (GSFC) report:

We observed the field of GRB 150811A (Evans, et al., GCN 18119) with the
Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the
1.5m Harold Johnson Telescope at the Observatorio AstronÃ³mico Nacional on
Sierra San Pedro MÃ¡rtir from 2015/08 11.17 to 2015/08 11.19 UTC (2.6
minutes to 0.47 hours after the BAT trigger), obtaining a total of 0.36
hours exposure in the r, i, and z bands.

We detect a highly-time-variable uncatalogued source within Swift-XRT error
circle.  In comparison with the USNO-B1 catalog, we obtain the following:

  r     17.51 +/- 0.01
  i     17.22 +/- 0.01
  z     16.76 +/- 0.04

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.  The source is located at RA, Dec =
19:25:21.40, -15:25:30.2 (J2000, +/-0.5").

We thank the staff of the Observatorio AstronÃ³mico Nacional in San Pedro
MÃ¡rtir.  Further observations are planned.


GRB_name: GRB150811A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18121
SUBJECT: GRB 150811A: KAIT optical candidate
DATE:    15/08/11 05:06:41 GMT
FROM:    Weikang Zheng at UC Berkeley  <weikang@berkeley.edu>

WeiKang Zheng (UC Berkeley), Xianggao Wang (UC Berkeley, GXU, UNLV)
and Alexei V. Filippenko (UC Berkeley) report on behalf of the
KAIT GRB team:

The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, responded to Swift GRB 150811A (Evans et al.,
GCN 18119) about 10 minutes after the burst. Observations were
performed with an automatic sequence in the clear (roughly R), V,
and I filters, and the exposure time was 20 s per image. 
Inside the XRT error circle we detected an un-cataloged source with
coordinates of :

RA =  19:25:21.40 (J2000)
DEC= -15:25:30.96 (J2000)

The object has I band mag of ~16.5 at ~15 minutes after
burst and is decaying. We suggest this is the afterglow of GRB 150811A.
Follow-up observations are encouraged.


GRB_name: GRB150811A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18122
SUBJECT: GRB 150811A: Swift/UVOT Detection
DATE:    15/08/11 08:02:52 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

Paul Kuin (MSSL/UCL) and P. A. Evans (U Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150811A
147 s after the BAT trigger (Evans et al., GCN Circ. 18119). A source
consistent with the XRT position and the optical transient reported
by Butler et al.(GCN Circ. 18120) and Zheng et al. (GCN Circ. 18121)
is detected in the promptly available UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  19:25:21.4
    Dec (J2000) = -15:25:31.1
with an estimated uncertainty of 0.6 arc sec. (radius, 90% confidence).

The transient source is at a distance of 4.6 arcsec of a weak nearby
source.

Preliminary detections for the White and U finding charts using the
UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc.
1358, 373) for the early exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white_FC           147          297          147         20.43 +/- 0.23
u_FC               306          549          241         18.24 +/- 0.11

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.17 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB150811A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18123
SUBJECT: GRB 150811A: LCOGT-McDonald afterglow detection
DATE:    15/08/11 08:48:37 GMT
FROM:    Jure Japelj at U. of Ljubljana,Slovenia  <jure.japelj@fmf.uni-lj.si>

J. Japelj (U. Ljubljana), C. Guidorzi (U. Ferrara), S. Kobayashi (LJMU)
on behalf of a large collaboration report:

We observed the position of GRB 150811A (Evans et al. GCN Circ.
18119) with the 1-m McDonald telescope (Fort Davis, US), a
member of the Las Cumbres Observatory network. Observations
started on August 11 at 06:13:35 UT, i.e., 127 minutes after
the GRB trigger time and were done with the r' and i' filters.

We detect the optical afterglow (Butler et al. GCN 18120, Zheng
et al. GCN 18121, Kuin et al. 18122) with the magnitude of
r' = 18.4 +- 0.2 at 132 min after the GRB trigger. Magnitude has
been calibrated against nearby USNOB-1 stars.


GRB_name: GRB150811A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18124
SUBJECT: GRB 150811A: Enhanced Swift-XRT position
DATE:    15/08/11 13:18:27 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 1486 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 150811A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 291.33914, -15.42545 which is equivalent
to:

RA (J2000): 19h 25m 21.39s
Dec (J2000): -15d 25' 31.6"

with an uncertainty of 2.5 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.


GRB_name: GRB150811A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18125
SUBJECT: GRB 150811A: P60 Observations
DATE:    15/08/11 13:46:42 GMT
FROM:    S. Bradley Cenko at NASA/GSFC  <brad.cenko@nasa.gov>

D. A. Perley (DARK) and S. B. Cenko (GSFC) report:

The Palomar 60-inch automated telescope responded to the trigger for GRB 150811A (Evans et al., GRB 18119) and began observations at 04:10:54 UT, 4.75 minutes after the burst.  A sequence of four 60-second i-band images was acquired, followed by a repeating cycle of 60-second r, i, and z-band images, then two epochs of imaging in ri filters later in the night.

The optical afterglow (e.g. Butler et al, GCN 18120; Zheng et al., GCN 18121; Kuin et al., GCN 18122; Japelj et al., GCN 18123) shows a sharp rise in flux during the first few observations, from I ~ 17.5 mag at t_mid = 5.25 minutes to a peak of I ~ 16.2 mag at t = 12.42 minutes (calibrating to USNO B1 I-band standards).  Afterwards it levels out and then declines steadily, reaching I ~ 18.3 mag at t = 135.1 min and I ~ 19.0 mag at t = 303.85 min, corresponding to an average decay rate of approximately alpha = 0.8.

Further follow-up is planned.  Spectroscopy is highly encouraged.


GRB_name: GRB150810A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18126
SUBJECT: GRB 150810A: Fermi GBM detection
DATE:    15/08/11 16:14:52 GMT
FROM:    Oliver Roberts at UCD/Fermi  <oliver.roberts@ucd.ie>

O.J. Roberts (UCD) reports on behalf of the Fermi GBM team:

"At 11:38:08.91 on August 10th 2015, the Fermi Gamma-Ray
Burst Monitor triggered and located GRB 150810A (trigger
460899492/150810485). The GBM on-ground location, using
the Fermi GBM trigger data, is RA = 283.20, Dec = +21.18
with an uncertainty of 3 degrees (radius, 1-sigma containment,
statistical only; there is additionally a systematic error which
is currently estimated to be 2 to 3 degrees).

The angle of the burst direction to the Fermi LAT boresight is
62 degrees.

The GBM light curve consists of two unresolved peaks with a
duration of about 0.5s (50-300 keV). The time-averaged
spectrum from T0-0.064s to T0+0.448s is best fit by a power
law with an exponential high-energy cutoff. The power law index
is -0.68 +/- 0.05 and the cutoff energy, parameterized as
Epeak, is 1294 +/-159 keV.

The event fluence (10-1000 keV) in this time interval is
(1.87 +/- 0.04)E-06 erg/cm^2. The 64 ms peak photon flux
measured starting from T0+0s in the 10-1000 keV band is
17.9 +/- 1.1 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."


GRB_name: GRB150811A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18127
SUBJECT: GRB 150811A: Swift-XRT refined Analysis
DATE:    15/08/11 16:21:02 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

D.N. Burrows (PSU), C. Pagani (U. Leicester), A.P. Beardmore (U.
Leicester), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia
(ASDC), T.G.R. Roegiers (PSU), L.M. McCauley (PSU) and P.A. Evans
report on behalf of the Swift-XRT team:

We have analysed 8.5 ks of XRT data for GRB 150811A (Evans et al. GCN
Circ. 18119), from 128 s to 27.8 ks after the  BAT trigger. The data
comprise 156 s in Windowed Timing (WT) mode (the first 9 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Goad et al.
(GCN Circ. 18124).

The light curve can be modelled with an initial power-law decay with an
index of alpha=2.52 (+/-0.19), followed by a break at T+366 s to an
alpha of 1.17 (+0.06, -0.10).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.11 (+0.21, -0.13). The
best-fitting absorption column is  1.60 (+0.65, -0.07) x 10^21 cm^-2,
consistent with the Galactic value of 1.5 x 10^21 cm^-2 (Willingale et
al. 2013). The PC mode spectrum has a photon index of 2.03 (+0.13,
-0.15) and a best-fitting absorption column of 2.1 (+1.0, -0.6) x 10^21
cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 3.5 x 10^-11 (4.9 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      2.1 (+1.0, -0.6) x 10^21 cm^-2
Galactic foreground: 1.5 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:      2.03 (+0.13, -0.15)

If the light curve continues to decay with a power-law decay index of
1.17, the count rate at T+24 hours will be 3.2 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.1 x
10^-13 (1.6 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00651882.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB150811A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18128
SUBJECT: GRB 150811A: SAO RAS optical observations
DATE:    15/08/11 21:44:15 GMT
FROM:    Moskvitin Alexander at SAO RAS  <mosk@sao.ru>

A. S. Moskvitin (SAO RAS, Russia) report on behalf
of larger GRB follow-up collaboration:

The field of the GRB 150811A (Evans et al., GCNC #18119)
was observed with the Zeiss-1000, 1-m telescope of SAO RAS.
The observations started since 13.6 hours after the trigger.
6 x 300 sec frames in Rc filter were obtained under the
good weather conditions.

The OT (Butler et al., GCNC #18120; Zheng, Wang and Filippenko,
GCNC #18121; Kuin and Evans, GCNC #18122; Japelj, Guidorzi
and Kobayashi, GCNC #18123; Perley and Cenko, GCNC #18125)
is clearly detected in our stack image close to USNO-B1.0
star 0745-0762543. PSF photometry of the OT with DAOPHOT package
gives R = 20.74 +/- 0.12 (T_mid - T0 = 13.911 hours).

Photometry is based on the nearby USNO-B1 stars (R2 magnitudes).
The magnitude of the OT is not corrected for the Galactic extinction.


GRB_name: GRB150811A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18129
SUBJECT: GRB 150811A: Swift-BAT refined analysis
DATE:    15/08/11 22:09:07 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC),
J. R. Cummings (GSFC/UMBC), P. A. Evans (U Leicester),
N. Gehrels (GSFC), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU),
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 150811A (trigger #651882)
(Evans, et al., GCN Circ. 18119).  The BAT ground-calculated position is
RA, Dec = 291.347, -15.434 deg which is
  RA(J2000)  =  19h 25m 23.3s
  Dec(J2000) = -15d 26' 00.8"
with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 67%.

The mask-weighted light curve shows a single FRED-like pulse that starts
at ~T+1 s, peaks at ~T+6 s, and ends at ~T+40 s. T90 (15-350 keV)
is 34.00 +- 6.25 sec (estimated error including systematics).

The time-averaged spectrum from T+1.51 to T+40.36 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.13 +- 0.27.  The fluence in the 15-150 keV band is 4.9 +- 0.8 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+6.59 sec in the 15-150 keV band
is 0.5 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/651882/BA/


GRB_name: GRB150811B
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18130
SUBJECT: GRB 150811B: Fermi GBM detection
DATE:    15/08/12 02:59:05 GMT
FROM:    Peter Jenke at MSFC  <peter.a.jenke@nasa.gov>

P. Jenke (UAH) reports on behalf of the Fermi GBM Team:

"At 20:22:13.75 UT on August 11 2015, the Fermi Gamma-Ray Burst 
Monitor triggered and located 
GRB 150811B (trigger 461017337/150811849). 
The GBM on-ground location, using the Fermi GBM trigger data, 
is RA = 188.0, Dec = -13.5 (J2000 degrees, equivalent to 
12h 32m 00s, -13d 30'), with an uncertainty of 8.7 
degree (radius, 1-sigma containment,
statistical only; there is additionally a systematic error which is
currently estimated to be 2 to 3 degrees).

The angle of the burst direction to the Fermi LAT boresight is 
108 degrees.

The GBM light curve consists of a single peak with a duration
(T90) of about 0.6 s (50-300 keV).
The time-averaged spectrum from T0-0.13 s to T0+0.64 s is
adequately fit by a Band function with Epeak = 1300 +/- 100 keV,
Alpha =-0.23 +/- 0.07 and Beta = -3.0 +/- 0.2.

The event fluence (10-1000 keV) in this time interval is
(1.6 +/- 0.1)E-07 erg/cm^2. The 64 ms peak photon flux measured
starting from T0-0.13 s in the 10-1000 keV band
is 8.6 +/- 0.3 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."


GRB_name: GRB150811A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18131
SUBJECT: GRB 150811A: Swift/UVOT further observations
DATE:    15/08/12 12:14:43 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

N. P. M. Kuin (UCL-MSSL) and P. A. Evans (U Leicester)
report on behalf of the Swift/UVOT team:

We report further on the Swift/UVOT observations of GRB 150811A which
began 148 s after the BAT trigger (Evans et al., GCN Circ. 18119).
A source consistent with the XRT position (Goad et al. GCN Circ. 18124)
was reported earlier in the optical/ir by Butler et al.(GCN Circ. 18120)
Zheng et al. (GCN Circ. 18121), Kuin et al.(GCN Circ. 12122), Japelj et
al., (GCN Circ. 12123),  Perley and Cenko (GCN. Circ. 12125), Moskivitin
(GCN Circ. 12128). Our initial observations in the white filter show a
rise from the start at 147s around magnitude (white) 21 which continues
in the u band event data and starts leveling off around magnitude 17.8
550s after the trigger, consistent with the report by Perley and Cenko.
The data taken during the next orbit show that  the decay had already
set in. The uv bands showed marginal count rates in all three bands
initially below the 3-sigma level, suggesting the burst is at low redshift.


Preliminary detections and 3-sigma upper limits using the UVOT photometric
system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early
exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white_FC           148          297          147         20.39 +/- 0.23
u_FC               306          549          239         18.19 +/- 0.11
white             4424         4624          197         19.16 +/- 0.07
u                 5449         5854          197         18.83 +/- 0.16
v                 4835         5034          197         18.89 +/- 0.17
b                 4219         4419          197         19.31 +/- 0.14
w1                5244        11888         1082        >20.6
m2                5039        10981         1082        >21.1
w2                4630         6265          393        >20.5

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.17 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB150811A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18132
SUBJECT: GRB 150811A: Continued RATIR Observations
DATE:    15/08/12 18:18:04 GMT
FROM:    Nat Butler at UC berkeley  <natxbutler@gmail.com>

Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William
H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB),
J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara
(ORAU/GSFC), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico
Ramirez-Ruiz (UCSC), JosÃ© A. de Diego (UNAM), Leonid Georgiev (UNAM), JesÃºs
GonzÃ¡lez (UNAM), Carlos RomÃ¡n-ZÃºÃ±iga (UNAM), Neil Gehrels (GSFC), and
Harvey Moseley (GSFC) report:

We observed the field of GRB 150811A (Evans, et al., GCN 18119) with the
Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the
1.5m Harold Johnson Telescope at the Observatorio AstronÃ³mico Nacional on
Sierra San Pedro MÃ¡rtir from 2015/08 12.15 to 2015/08 12.41 UTC (23.39 to
29.66 hours after the BAT trigger), obtaining a total of 4.98 hours
exposure in the r, i, and z bands.

We continue to detect the source we reported earlier (Butler, et al.; GCN
18120), which we also observed for several additional hours on the first
night.  In comparison with the USNO-B1 and 2MASS catalogs, we obtain the
following detections and upper limit (3-sigma):

  r 21.68 +/- 0.14
  i 21.48 +/- 0.05
  z >18.9

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.  In comparison with our previous
observations, the source flux has declined approximately as t^(-1).

We thank the staff of the Observatorio AstronÃ³mico Nacional in San Pedro
MÃ¡rtir.  Further observations are planned.


GRB_name: GRB150811B
Detection_method: IPN Triangulation
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18133
SUBJECT: IPN Triangulation of GRB 150811B
DATE:    15/08/12 18:38:22 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

S. Golenetskii, R. Aptekar, V. Pal'shin, D. Frederiks,
D. Svinkin, and T. Cline on behalf of the Konus-Wind team,

K. Hurley, on behalf of the IPN,

V. Connaughton, M. S. Briggs, C. Meegan, V. Pelassa,
and A. Goldstein, on behalf of the Fermi GBM team, and

A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
report:

The short-duration GRB 150811B has been detected by Fermi (GBM: Jenke, 
GCN Circ. 18130), Konus-Wind, and INTEGRAL (SPI-ACS), so far, at about 
73334 s UT (20:22:14).

We have triangulated it to a preliminary, 3 sigma error box whose 
coordinates are:
---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   186.348 (12h 25m 23s) -14.105 (-14d 06' 20")
  Corners:
   184.572 (12h 18m 17s) -16.337 (-16d 20' 12")
   188.337 (12h 33m 21s) -12.037 (-12d 02' 14")
   187.888 (12h 31m 33s) -11.720 (-11d 43' 10")
   184.110 (12h 16m 26s) -16.010 (-16d 00' 36")
  ---------------------------------------------
The error box area is 3.1 sq. deg, and its maximum
dimension is 5.7 deg (the minimum one is 32.5 arcmin).
The Sun distance was 52 deg.

This box may be improved.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB150811_T73329/IPN/

The Konus-Wind time history and spectrum will be given in a forthcoming 
GCN Circular.


GRB_name: GRB150811A
Detection_method: VLA Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18134
SUBJECT: GRB 150811A: VLA Detection
DATE:    15/08/12 20:11:53 GMT
FROM:    Tanmoy Laskar at Harvard U  <tanmoylaskar@gmail.com>

T. Laskar (NRAO / UC Berkeley), A. Zauderer, K. Alexander, E. Berger
(Harvard), and W. Fong (Univ. of Arizona) report on behalf of a larger
collaboration:

"We observed GRB 150811A (Evans et al; GCN 18119) at multiple frequencies
with the VLA beginning 2015 August 12.13 UT (0.96 days after the burst). At
a mean frequency of 21.8 GHz, we detect a radio source with a preliminary
flux density of ~ 0.1 mJy at

RA = 19:25:21.3920 +/- 0.0005
Dec = -15:25:31.00 +/- 0.01

consistent with the enhanced Swft/XRT position (Goad et al.; GCN 18124) and
the optical position (Butler et al., GCN 18120; Zheng at al., GCN 18121;
Kuin et al., GCN 18122). Follow-up observations are planned."


GRB_name: GRB150811A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18135
SUBJECT: GRB 150811A: KAIT Refined Analysis
DATE:    15/08/12 21:40:27 GMT
FROM:    Xiang-Gao Wang at GuangXi U  <wangxg@gxu.edu.cn>

Xianggao Wang (UC Berkeley, GXU, UNLV), WeiKang Zheng and
Alexei V. Filippenko (UC Berkeley) report on behalf of the 
KAIT GRB team:

The 0.76-m Katzman Automatic Imaging Telescope (KAIT) at
Lick Observatory responded to Swift GRB 150811A (Evans et al.,
GCN 18119) starting at 04:09:05 UT, 176 s after the burst.
Observations were performed with an automatic sequence in the
V, I, and clear (roughly R) filters, and the exposure time was
20 s per image. Due to a focus problem, the first useful image
started at about 364 s after burst, and observations lasted
about 5.5 hours later. The optical afterglow (Butler et al.,
GCN 18120; GCN 18132, Zheng et al., GCN 18121, Kuin et al., GCN
18122; 18131, Japelj et al., GCN 12123, Perley & Cenko, GCN 12125,
Moskivitin, GCN 12128) was well detected in I filters.
We confirm the peak of the OT around ~13 m reported by
Perley & Cenko (GCN 12125). After 3 ks after the burst, the
light curve can be fit by a power law with index of -1.02,
consistent with the value reported by Butler et al. (GCN 18132).
A preliminary light curve is posted at:
http://astro.berkeley.edu/~zwk/grb/GRB150811A/GRB150811A_kait.png





  


GRB_name: GRB150811B
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18137
SUBJECT: Konus-Wind observation of GRB 150811B
DATE:    15/08/13 13:43:58 GMT
FROM:    Anastasia Tsvetkova at Ioffe Institute  <tsvetkova@mail.ioffe.ru>

S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline
on behalf of the Konus-Wind team, report:

The short-duration, hard-spectrum, intense GRB 150811B
(Fermi GBM detection: Jenke, GCN 18130;
IPN triangulation: Golenetskii et al., GCN 18133)
triggered Konus-Wind at T0=73329.515 s UT (20:22:09.515).

The burst light curve shows a single pulse with a duration of ~0.7 s.
The emission is seen up to ~10 MeV.

As observed by Konus-Wind, the burst
had a fluence of 9.08(-1.11,+1.22)x10^-6 erg/cm2,
and a 16-ms peak energy flux, measured from T0+0.232 s,
of 2.89(-0.92,+0.95)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the burst
(measured from T0 to T0+0.256 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.35(-0.24,+0.29),
and Ep = 1197(-220,+299) keV (chi2 = 28/27 dof).
Fitting by the GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index:
beta < -2.51 (chi2 = 28/26 dof).

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB150811_T73329/

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.


GRB_name: GRB150811A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18140
SUBJECT: GRB 150811A: Continued RATIR Observations
DATE:    15/08/13 19:28:24 GMT
FROM:    Nat Butler at Az State U  <natbutler@asu.edu>

Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William
H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB),
J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara
(ORAU/GSFC), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico
Ramirez-Ruiz (UCSC), JosÃƒÂ© A. de Diego (UNAM), Leonid Georgiev (UNAM), JesÃƒÂºs
GonzÃƒÂ¡lez (UNAM), Carlos RomÃƒÂ¡n-ZÃƒÂºÃƒÂ±iga (UNAM), Neil Gehrels (GSFC), and
Harvey Moseley (GSFC) report:

We observed the field of GRB 150811A (Evans, et al., GCN 18119) with the
Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the
1.5m Harold Johnson Telescope at the Observatorio AstronÃƒÂ³mico Nacional on
Sierra San Pedro MÃƒÂ¡rtir from 2015/08 13.14 to 2015/08 13.40 UTC (47.37 to
53.59 hours after the BAT trigger), obtaining a total of 4.93 hours
exposure in the r, i, and z bands.

We continue to detect the optical afterglow.  Relative to the flux reported
in Butler et al. (GCN 18132), the source continues to appear to fade
approximately as t^(-1).  In comparison with the USNO-B1 and 2MASS
catalogs, we obtain the following detections and upper limit (3-sigma):

  r = 22.00 +/- 0.20
  i = 21.83 +/- 0.20
  z > 20.40

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.

We thank the staff of the Observatorio AstronÃƒÂ³mico Nacional in San Pedro
 MÃƒÂ¡rtir.


GRB_name: GRB150811A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18141
SUBJECT: GRB 150811A: Continued RATIR Observations
DATE:    15/08/14 20:01:44 GMT
FROM:    Nat Butler at UC berkeley  <natxbutler@gmail.com>

Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William
H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (UCB), J. Xavier Prochaska
(UCSC), Josh Bloom (UCB), Antonino Cucchiara (ORAU/GSFC), Eleonora Troja
(GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), JosÃ© A. de
Diego (UNAM), Leonid Georgiev (UNAM), JesÃºs GonzÃ¡lez (UNAM), Carlos
RomÃ¡n-ZÃºÃ±iga (UNAM), Neil Gehrels (GSFC), Harvey Moseley (GSFC), John
Capone (UMD), V. Zach Golkhou (ASU), and Vicki Toy (UMD) report:

We observed the field of GRB 150811A (Evans, et al., GCN 18119) with the
Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the
1.5m Harold Johnson Telescope at the Observatorio AstronÃ³mico Nacional on
Sierra San Pedro MÃ¡rtir from 2015/08 14.22 to 2015/08 14.41 UTC (73.12 to
77.68 hours after the BAT trigger), obtaining a total of 3.56 hours
exposure in the r, i, and z bands.

In comparison with the USNO-B1 and 2MASS catalogs, we obtain the following
detections and upper limit (3-sigma):

  r = 22.4 +/- 0.3
  i = 22.0 +/- 0.4
  z > 20.37

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.  The fading of the source remains
consistent with t^(-1) (see, Butler et al., 18120, 18132, 18140).

We thank the staff of the Observatorio AstronÃ³mico Nacional in San Pedro
MÃ¡rtir.


GRB_name: GRB150817A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18143
SUBJECT: GRB 150817A: Swift detection of a burst
DATE:    15/08/17 02:14:02 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

V. D'Elia (ASDC), S. D. Barthelmy (GSFC), N. Gehrels (NASA/GSFC),
L. Izzo (URoma/ICRA), J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC),
D. M. Palmer (LANL), B. Sbarufatti (INAF-OAB/PSU) and
M. H. Siegel (PSU) report on behalf of the Swift Team:

At 02:05:13 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150817A (trigger=652334).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 249.643, -12.066 which is 
   RA(J2000) = 16h 38m 34s
   Dec(J2000) = -12d 03' 55"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex
structure with a duration of at least 50 sec.  The peak count rate
was ~17000 counts/sec (15-350 keV), at ~11 sec after the trigger. 

The XRT began observing the field at 02:06:18.2 UT, 64.9 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 249.63352, -12.05336 which
is equivalent to:
   RA(J2000)  = 16h 38m 32.04s
   Dec(J2000) = -12d 03' 12.1"
with an uncertainty of 3.8 arcseconds (radius, 90% containment). This
location is 56 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper.  We
cannot determine whether the source is fading at the present time. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (2.71 x
10^21 cm^-2, Willingale et al. 2013), with an excess column of 4.5
(+3.63/-3.05) x 10^21 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 1.27e-09 erg cm^-2 s^-1 (0.2-10
keV). 

There will be no prompt UVOT data available for this burst. 

Burst Advocate for this burst is V. D'Elia (delia AT asdc.asi.it). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)


GRB_name: GRB150817A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18144
SUBJECT: GRB 150817A: RATIR Optical Afterglow Candidate
DATE:    15/08/17 04:02:40 GMT
FROM:    Nat Butler at UC berkeley  <natxbutler@gmail.com>

Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (UCB), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (ORAU/GSFC), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jos A. de Diego (UNAM), Leonid Georgiev (UNAM), Jess Gonzlez (UNAM), Carlos Romn-Ziga (UNAM), Neil Gehrels (GSFC), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (ASU), and Vicki Toy (UMD) report:

We observed the field of GRB 150817A (V. D'Elia, et al., GCN 18143) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astronmico Nacional on Sierra San Pedro Mrtir from 2015/08 17.14 to 2015/08 17.16 UTC (1.29 to 1.70 hours after the BAT trigger), obtaining a total of 0.36 hours exposure in the r, i, and z bands.

We find an uncatalogued source within the Swift-XRT error circle at RA, Dec = 16:38:31.98, -12:3:11.5 (J2000, +/-0.5").  In comparison with the USNO-B1 and 2MASS catalogs, we obtain the following detections and upper limit (3-sigma):

   r = 21.50 +/- 0.20
   i = 21.26 +/- 0.10
   z > 17.83

These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB.

Further observations are planned.

We thank the staff of the Observatorio Astronmico Nacional in San Pedro Mrtir.


GRB_name: GRB150817A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18145
SUBJECT: GRB 150817A: Continued RATIR Observations, Revised Candidate
DATE:    15/08/17 06:16:09 GMT
FROM:    Nat Butler at UC berkeley  <natxbutler@gmail.com>

Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (UCB), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (ORAU/GSFC), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jos A. de Diego (UNAM), Leonid Georgiev (UNAM), Jess Gonzlez (UNAM), Carlos Romn-Ziga (UNAM), Neil Gehrels (GSFC), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (ASU), and Vicki Toy (UMD) report:

We continue to observe the field of GRB 150817A (V. D'Elia, et al., GCN 18143) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astronmico Nacional on Sierra San Pedro Mrtir from 2015/08 17.14 to 2015/08 17.25 UTC (1.29 to 3.93 hours after the BAT trigger), obtaining a total of 2.13 hours exposure in the r, i, and z bands.

We note that the source reported in Butler et al. (GCN 18144) appears to have remained constant in flux over the time period quoted above, while an uncatalogued source just west of the XRT error circle has faded strongly as t^(-0.8+/-0.1).  This second source is located at RA, Dec = 16:38:31.51, -12:03:9.6 (J2000, +/-0.5").

In comparison with the USNO-B1 and 2MASS catalogs, we obtain the following detections and upper limit (3-sigma):

   r = 22.06 +/- 0.09
   i = 21.49 +/- 0.07
   z > 20.33

These magnitudes, corresponding to the midpoint of our observation, are in the AB system and are not corrected for Galactic extinction in the direction of the GRB.

We thank the staff of the Observatorio Astronmico Nacional in San Pedro Mrtir.


GRB_name: GRB150817A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18146
SUBJECT: GRB 150817A: Enhanced Swift-XRT position
DATE:    15/08/17 10:18:51 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 1629 s of XRT Photon Counting mode data and 4 UVOT
images for GRB 150817A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 249.63108, -12.05293 which is equivalent
to:

RA (J2000): 16h 38m 31.46s
Dec (J2000): -12d 03' 10.5"

with an uncertainty of 1.7 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.


GRB_name: GRB150817A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18147
SUBJECT: GRB 150817A: Swift-XRT refined Analysis
DATE:    15/08/17 14:14:02 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), B.P. Gompertz
(U. Leicester), P. D'Avanzo (INAF-OAB), A. D'ai (INAF-IASFPA), T.G.R.
Roegiers (PSU), L.M. McCauley (PSU), J.A. Kennea (PSU) and V. D'Elia
report on behalf of the Swift-XRT team:

We have analysed 11 ks of XRT data for GRB 150817A (D'Elia et al. GCN
Circ. 18143), from 56 s to 29.2 ks after the  BAT trigger. The data
comprise 32 s in Windowed Timing (WT) mode (the first 7 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Osborne et
al. (GCN Circ. 18146).

The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=3.6 (+/-0.4). At T+104 s  the decay
flattens to an alpha of 0.57 (+0.06, -1.00) before breaking again at
T+4285 s to a final decay with index alpha=1.07 (+/-0.07).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.77 (+/-0.11). The
best-fitting absorption column is  4.5 (+0.7, -0.6) x 10^21 cm^-2, in
excess of the Galactic value of 2.7 x 10^21 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 4.5 x 10^-11 (6.4 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      4.5 (+0.7, -0.6) x 10^21 cm^-2
Galactic foreground: 2.7 x 10^21 cm^-2
Excess significance: 4.6 sigma
Photon index:      1.77 (+/-0.11)

If the light curve continues to decay with a power-law decay index of
1.07, the count rate at T+24 hours will be 0.021 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 9.7 x
10^-13 (1.4 x 10^-12) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00652334.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB150817A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18148
SUBJECT: GRB 150817A: Swift-BAT refined analysis
DATE:    15/08/17 14:18:27 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>

C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC),
V. D'Elia (ASDC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
 
Using the data set from T-239 to T+963 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 150817A (trigger #652334)
(D'Elia, et al., GCN Circ. 18143).  The BAT ground-calculated position is
RA, Dec = 249.635, -12.050 deg, which is 
   RA(J2000)  =  16h 38m 32.3s 
   Dec(J2000) = -12d 03' 01.7" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 71%.
 
The mask-weighted light curve shows multiple strong peaks starting at ~T-20,
with the brightest peak at ~T+12 sec and ending at ~T+70 sec.
T90 (15-350 keV) is 38.8 +- 2.1 sec (estimated error including systematics).
 
The time-averaged spectrum from T-16.76 to T+53.28 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.78 +- 0.04.  The fluence in the 15-150 keV band is 5.9 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+11.22 sec in the 15-150 keV band
is 9.6 +- 0.3 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level. 
 
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/652334/BA/


GRB_name: GRB150817A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18149
SUBJECT: GRB 150817A: Fermi GBM observation
DATE:    15/08/17 15:37:57 GMT
FROM:    Hoi-Fung Yu at MPE  <sptfung@mpe.mpg.de>

H.-F. Yu (MPE) and P. Jenke (UAH) report on behalf of the Fermi GBM Team: 

"At 02:05:08.40 UT on 17 August 2015, the Fermi Gamma-Ray Burst Monitor 
triggered and located GRB 150817A (trigger 461469912 / 150817087), 
which was also detected by the Swift/BAT (D'Elia et al. 2015, GCN 18143). 
The GBM on-ground location is consistent with the Swift position. 

The angle from the Fermi LAT boresight at the GBM trigger time is 102 degrees. 

This burst was also independently detected by INTEGRAL SPI-ACS. 

The GBM light curve consists of multiple peaks with a duration (T90) 
of about 36 s (50-300 keV). The time-averaged spectrum from 
T0-10.240 s to T0+45.057 s is best fit by a power law function with 
an exponential high-energy cutoff. The power law index is -1.34 +/- 0.06 
and the cutoff energy, parameterized as Epeak, is 109.0 +/- 8.8 keV. 

The event fluence (10-1000 keV) in this time interval 
is (1.15 +/- 0.05)E-05 erg/cm^2. The 1.024-sec peak photon flux 
measured starting from T0+16.256 s in the 10-1000 keV band 
is 15.7 +/- 0.4 ph/s/cm^2. 

The spectral analysis results presented above are preliminary; 
final results will be published in the GBM GRB Catalog."


GRB_name: GRB150817A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18150
SUBJECT: GRB 150817A: Swift/UVOT Upper Limits
DATE:    15/08/17 16:34:51 GMT
FROM:    Frank Marshall at GSFC  <femarsha@khamseen.gsfc.nasa.gov>

F. E. Marshall (NASA/GSFC) and V. D'Elia (ASDC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150817A
3955 s after the BAT trigger (D'Elia et al., GCN Circ. 18143).
No optical afterglow consistent with the enhanced X-ray
position (Osborne et al. GCN Circ. 18146) or
the optical position (Butler et al. GCN Circ. 18145)
is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC          3955         4104          147         >20.5
white             3955        12079          930         >21.4
v                 4111        28678         1278         >20.9
b                 4932        17880         1723         >21.7
u                 4727        23627         2613         >21.7
w1                4522        22957         2144         >21.0
w2               26865        27765          886         >20.5

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.48 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB150818A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18152
SUBJECT: GRB 150818A: Swift detection of a burst
DATE:    15/08/18 11:53:55 GMT
FROM:    Kim Page at U.of Leicester  <klp5@leicester.ac.uk>

V. D'Elia (ASDC), A. A. Breeveld (UCL-MSSL),
P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC),
L. Izzo (URoma/ICRA), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester) and B. Sbarufatti (INAF-OAB/PSU) report on
behalf of the Swift Team:

At 11:36:32 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150818A (trigger=652603).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 230.446, +68.342 which is 
   RA(J2000) = 15h 21m 47s
   Dec(J2000) = +68d 20' 32"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single-peaked
structure with a duration of about 50 sec.  The peak count rate
was ~1990 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 11:37:57.3 UT, 84.5 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 230.3621, 68.3446 which is equivalent to:
   RA(J2000)  = +15h 21m 26.90s
   Dec(J2000) = +68d 20' 40.6"
with an uncertainty of 6.1 arcseconds (radius, 90% containment). This
location is 111 arcseconds from the BAT onboard position, within the
BAT error circle. No event data are yet available to determine the
column density using X-ray spectroscopy. 

UVOT took a finding chart exposure of  28 seconds with the White
filter  starting 94 seconds after the BAT trigger. No credible
afterglow candidate has  been found in the initial data products. The
2.7'x2.7' sub-image processing  failed because of no aspect solution
is available.   Results from the list of sources  generated on-board
are not available at this time. 

Burst Advocate for this burst is V. D'Elia (delia AT asdc.asi.it). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)


GRB_name: GRB150817A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18153
SUBJECT: GRB 150817A: P60 Observations
DATE:    15/08/18 13:30:21 GMT
FROM:    S. Bradley Cenko at NASA/GSFC  <brad.cenko@nasa.gov>

S. B. Cenko (NASA/GSFC) and D. A. Perley (DARK) report on behalf of a larger collaboration:

We observed the location of GRB150817A (DElia et al., GCN 18143) with the robotic Palomar 60 inch telescope (P60).  Observations began at 3:35 UT on 2015 Aug 17 (~ 90 min after the Swift trigger time).  We detect a faint source at the location of the (second) candidate optical afterglow from RATIR (Butler et al., GCN 18145).  Using nearby point sources from the APASS survey, we measure an i-band magnitude of 21.42 +/- 0.11 in a stacked frame at a median epoch of dt = 125 min after the Swift trigger. 


GRB_name: GRB150818A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18154
SUBJECT: GRB 150818A: Planned XMM-Newton observation
DATE:    15/08/18 13:44:25 GMT
FROM:    Norbert Schartel at XMM-Newton/ESA  <too@xmm.esac.esa.int>

XMM-Newton will observe GRB 150818A at location
(RA=15h 21m 26.9s, DEC=68d 20' 40.5", J2000),
starting at 18:15:45 UT, on August 18, 2015,
for an exposure of 22400 seconds.





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GRB_name: GRB150818A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18155
SUBJECT: GRB 150818A: Swift/UVOT candidate afterglow
DATE:    15/08/18 14:59:35 GMT
FROM:    Frank Marshall at GSFC  <femarsha@khamseen.gsfc.nasa.gov>

F. E. Marshall (NASA/GSFC) and V. D'Elia (ASDC)
report on behalf of the Swift/UVOT team:

UVOT took a finding chart exposure of 28 seconds with the White filter
starting 94 seconds after the BAT trigger on GRB 150818A. 
There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =  15:21:25.48 = 230.35616
  DEC(J2000) =  68:20:34.0  = 68.34278
with a 90%-confidence error radius of about 1.0 arc sec. This position is 10
arcseconds from the center of the XRT error circle (D'Elia et al. GCN Circ. 18152). 
The estimated magnitude is 19.5 with a 1-sigma error of about 0.2. 
No correction has been made for extinction.


GRB_name: GRB150817A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18156
SUBJECT: GRB 150817A: Continued RATIR Optical Observations - Afterglow Confirmation
DATE:    15/08/18 16:29:47 GMT
FROM:    Alan M. Watson at Instituto de Astronomia UNAM  <alan@astro.unam.mx>

Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William 
H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (UCB), J. Xavier 
Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (ORAU/GSFC), 
Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), 
Jos A. de Diego (UNAM), Leonid Georgiev (UNAM), Jess Gonzlez (UNAM), 
Carlos Romn-Ziga (UNAM), Neil Gehrels (GSFC), Harvey Moseley (GSFC), 
John Capone (UMD), V. Zach Golkhou (ASU), and Vicki Toy (UMD) report:

We observed the field of GRB 150817A (D'Elia, et al., GCN 18143) with the 
Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 
1.5m Harold Johnson Telescope at the Observatorio Astronmico Nacional on 
Sierra San Pedro Mrtir from 2015/08 18.16 to 2015/08 18.27 UTC (25.78 to 
28.42 hours after the BAT trigger), obtaining a total of 1.77 hours 
exposure in the r, i, and z bands.

The first source reported by Butler et al. (GCN 18144) has not faded since 
our first epoch of observations.

The second source, reported by Butler et al. (GCN 18145), has continued to 
fade and is now only marginally detected. In comparison with the USNO-B1 
and 2MASS catalogs, we obtain the following marginal detections and upper 
limit (3-sigma):

   r = 23.8  0.4
   i = 23.8  0.3
   z > 20.2

These magnitudes are in the AB system and are not corrected for Galactic 
extinction in the direction of the GRB.

We note that the second source is consistent with the enhanced Swift-XRT 
error circle (Osborne et al. GCN 18146). This coincidence and the clear 
fading suggest that it is the afterglow of the GRB.

We thank the staff of the Observatorio Astronmico Nacional in San Pedro 
Mrtir.


GRB_name: GRB150818A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18157
SUBJECT: GRB 150818A: Swift-BAT refined analysis
DATE:    15/08/18 17:25:59 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>

D. M. Palmer (LANL), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC),
V. D'Elia (ASDC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), T. Sakamoto (AGU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
 
Using the data set from T-61 to T+242 sec from the recent telemetry downlinks,
we report further analysis of BAT GRB 150818A (trigger #652603)
(D'Elia, et al., GCN Circ. 18152).  The BAT ground-calculated position is
RA, Dec = 230.340, 68.342 deg, which is 
   RA(J2000)  =  15h 21m 21.7s 
   Dec(J2000) = +68d 20' 31.5" 
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 36%.
 
The mask-weighted light curves shows two overlapping peaks starting at ~T-25 sec,
peaking at ~T+1 sec, and ending at ~T+180 sec.
T90 (15-350 keV) is 123.3 +- 31.3 sec (estimated error including systematics).
 
The time-averaged spectrum from T-11.18 to T+165.12 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.96 +- 0.09.  The fluence in the 15-150 keV band is 4.1 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T-0.88 sec in the 15-150 keV band
is 2.4 +- 0.3 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level. 
 
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/652603/BA/


GRB_name: GRB150817A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18158
SUBJECT: GRB 150817A: LCOGT observations
DATE:    15/08/18 18:03:36 GMT
FROM:    Simone Dichiara at Ferrara U/Italy  <dichiara@fe.infn.it>

S. Dichiara, C. Guidorzi (U. Ferrara), C.G. Mundell (U. Bath),
S. Kobayashi (LJMU), A. Gomboc (U. Ljubljana) on behalf of
a large collaboration report:

The 1-m telescopes in Cerro Tololo (Chile) and McDonald (Texas)
 began observing Swift GRB 150817A (V. D'Elia, et al., GCN 18143).
on August 17 at 03:16:31 UT, i.e. ~70 minutes since the BAT trigger,
with the r' and i' filters. Further observations with the i' filter
were performed using the 2-m Faulkes Telescope North ~400 min after
the trigger.

Within the enhanced XRT error circle (Osborne et al. GCN Circ. 18146)
we find no optical counterpart to the following limiting magnitude:

Mid time from  Total Exp   Filter    Magnitude
trigger (min)   (s)
-------------------------------------------------
75.9         120x9       r'        > 19.6
86.3         120x8       i'        > 18.5
107.6        120x5       r'        > 19.7
119.2        120x5       i'        > 19.1
408.1        120x5       i'        > 20.7
-------------------------------------------------

Our results are consistent with the previous observations reported by
Butler et al. (GCN Circ. 18144) and Cenko et al. (GCN Circ. 18153).

Magnitudes are calibrated against nearby USNO-B1 stars (R2 and I).


GRB_name: GRB150818A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18159
SUBJECT: GRB 150818A: Enhanced Swift-XRT position
DATE:    15/08/18 18:09:34 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 2975 s of XRT Photon Counting mode data and 7 UVOT
images for GRB 150818A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 230.35595, +68.34204 which is equivalent
to:

RA (J2000): 15h 21m 25.43s
Dec (J2000): +68d 20' 31.4"

with an uncertainty of 1.7 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.


GRB_name: GRB150817A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18160
SUBJECT: GRB 150817A: AAO optical observations
DATE:    15/08/18 19:09:15 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

E. Mazaeva (IKI), R. Inasaridze (AAO), V. Ayvazian (AAO), I. Molotov 
(KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up 
collaboration:

We observed the field of the Swift GRB 150817A (Dâ€™Elia et al., GCN 
18143) with AS-32 (0.7m) telescope of Abastumani Observatory starting on 
Aug. 17 (UT) 17:00:31.  Within the enhanced XRT error circle (Osborne et 
al., GCN 18146) we do not detect the optical afterglow (Butler et al., 
GCN 18145; Cenko et al., GCN 18153). In particular the  magnitude of the 
first object (Butler et al., GCN 18144) is 21.6 +/- 0.2.  Upper limit of 
the object is following

Date       UT start    t-T0     Filter  Exp.     UL(3 sigam)
                        (mid, days)      (s)

2015-08-17 17:00:31    0.64432  None    24*120   22.4

The photometry is based on nearby USNO-B1.0 stars
USNO-B.1_id  R2
0779-0405699 16.12
0779-0405721 16.40
0779-0405742 16.47
0779-0405723 16.94
0779-0405664 17.60


GRB_name: GRB150818A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18161
SUBJECT: GRB 150818A: Swift/UVOT Detection
DATE:    15/08/18 20:39:33 GMT
FROM:    Marissa McCaule at PSU  <marissamc@swift.psu.edu>

L. M. McCauley (PSU), L. M. Z. Hagen (PSU), and V. D'Elia (ASDC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150818A
94 s after the BAT trigger (D'Elia et al., GCN Circ. 18152).
A source consistent with the XRT position (Beardmore et al. GCN Circ. 18159)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  15:21:25.43 = 230.35594 (deg.)
    Dec (J2000) = +68:20:33.0  =  68.34251 (deg.)
with an estimated uncertainty of 0.66 arc sec. (radius, 90% confidence).

Preliminary detections and 3-sigma upper limits using the UVOT photometric
system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early
exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white_fc            94          121           27         19.39+-0.25
white             3414         4790          344         19.92+-0.17
white            10222        10826          590         19.68+-0.07
v                 3572         5201          393        >19.36
b                 4385         4585          196        >20.16
b                 5821        10217          927         20.56+-0.33
u                 4180         4379          196        >19.66
u                 5616         5816          196         19.63+-0.25
uvw1              3976         4175          195         18.78+-0.20
uvw1              5411         5611          196         18.95+-0.20
uvm2              3776         3976          192         18.81+-0.23
uvm2              5206         5406          196         18.89+-0.24
uvw2              4796         4996          196         18.90+-0.19

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB150818A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18162
SUBJECT: GRB 150818A: Swift-XRT refined Analysis
DATE:    15/08/18 23:54:04 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P.A. Evans (U. Leicester), B.P. Gompertz (U. Leicester), A. D'ai
(INAF-IASFPA), A. Maselli  (INAF-IASFPA), L.M. McCauley (PSU), J.A.
Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), J.P. Osborne (U. Leicester)
and V. D'Elia report on behalf of the Swift-XRT team:

We have analysed 6.4 ks of XRT data for GRB 150818A (D'Elia et al. GCN
Circ. 18152), from 74 s to 21.7 ks after the  BAT trigger. The data
comprise 34 s in Windowed Timing (WT) mode (the first 9 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Beardmore
et al. (GCN Circ. 18159).

The late-time light curve (from T0+3.5 ks) can be modelled with a
power-law decay with a decay index of alpha=.

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.59 (+0.11, -0.10). The
best-fitting absorption column is  2.33 (+0.28, -0.27) x 10^21 cm^-2,
in excess of the Galactic value of 2.5 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.96 (+0.30, -0.27)
and a best-fitting absorption column of 7.6 (+7.6, -5.1) x 10^20 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 3.3 x 10^-11 (3.9 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      7.6 (+7.6, -5.1) x 10^20 cm^-2
Galactic foreground: 2.5 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:      1.96 (+0.30, -0.27)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00652603.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB150819A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18163
SUBJECT: GRB 150819A: Swift detection of a burst
DATE:    15/08/19 01:02:15 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC), D. N. Burrows (PSU),
S. B. Cenko (GSFC), V. D'Elia (ASDC), L. Izzo (URoma/ICRA),
J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC) and
B. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift Team:

At 00:50:08 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150819A (trigger=652643).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 42.337, +9.784 which is 
   RA(J2000)  =  02h 49m 21s
   Dec(J2000) = +09d 47' 02"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is typical for image triggers, the real-time
light curve does not show anything significant. 

The XRT began observing the field at 00:52:27.1 UT, 138.1 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source located at RA, Dec 42.33146, 9.80665 which is
equivalent to:
   RA(J2000)  = 02h 49m 19.55s
   Dec(J2000) = +09d 48' 23.9"
with an uncertainty of 3.8 arcseconds (radius, 90% containment). This
location is 83 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 1.85
x 10^21 cm^-2 (Willingale et al. 2013). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 142 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
The 8'x8' region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.22. 

Burst Advocate for this burst is T. N. Ukwatta (tilan.ukwatta AT gmail.com). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)


GRB_name: GRB150818A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18164
SUBJECT: GRB150818A: NOT imaging 
DATE:    15/08/19 01:04:40 GMT
FROM:    Steve Schulze at U of Iceland  <sts30@hi.is>

S. Schulze (PUC, MAS), J. P. U. Fynbo (DARK, NBI), T. Kruehler (MPE), D. Malesani, (DARK/NBI), I. V. Rasmussen, J. L. Marcher, L. L. Thomson (NBI), A. Djupvik (NOT), B. Milvang-Jensen (DARK/NBI) and P. Jakobsson (U Iceland) report on behalf a larger collaboration:

We observed the field of GRB 150818A (D'Elia et al., GCN 18152) with the Nordic Optical Telescope (NOT) equipped with ALFOSC. We obtained a 180 s and a 3x300 s image in R band. Observations started at 21:34 UT on August 18 (i.e. 9.62 hr after the burst).

We clearly detect the source reported in Marshall et al. (GCN 18155) and McCauley et al. (GCN 18161). We measure R=20.86 +/- 0.08 mag calibrated against several USNO stars. This value is not corrected for foreground extinction. 

Given the lack of evidence for variability (McCauley et al., GCN 18161), the association of this object with GRB 150818A remains unclear.


GRB_name: GRB150819A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18165
SUBJECT: GRB 150819A: Prompt enhanced Swift-XRT position
DATE:    15/08/19 01:29:35 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:

Using  promptly downlinked XRT event data for GRB 150819A, we find an
enhanced XRT position of the afterglow: RA, Dec: 42.3335, 9.8075 which
is equivalent to:
   RA (J2000)  = 02 49 20.03
   Dec (J2000) = +09 48 26.9
with an uncertainty of 2.0 arcseconds (radius, 90% confidence).
Analysis of the promptly available data is online at
http://www.swift.ac.uk/sper/652643.

Position enhancement is is described by Goad et al. (2007, A&A, 476,
1401) and Evans et al. (2009, MNRAS, 397, 1177).

This circular is an official product of the Swift-XRT team.


GRB_name: GRB150818A
Detection_method: correction
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18166
SUBJECT: GRB 150818A: Swift-XRT update, correction to GCN 18162
DATE:    15/08/19 07:17:42 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P.A. Evans (U, Leicester) reports on behalf of the Swift-XRT team:

Due to a computer error, the light curve decay index was missing in GCN 
18162.

At the present time, we have analysed 7.6 ks of XRT data for GRB 150818A 
(D'Elia et al. GCN Circ. 18152), from 74 s to 44.1 ks after the BAT trigger.

The XRT light curve can be modelled as a broken power-law, with an 
initial decay index of 2.36 (+0.08, -0.06), a break at T0 + 3600 
(+/-500) s, and a subsequent shallow decay of 0.66 (+0.16, -0.15).

If the decay continues at alpha=0.66, the predicted count-rate at T0+24 
hrs is 8.9e-3 ct/sec, which corresponds to an observed (unabsorbed) 
0.3-10 keV flux of 2.97e-13 (3.56e-13) erg/cm^2/s.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB150819A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18167
SUBJECT: GRB 150819A: Enhanced Swift-XRT position
DATE:    15/08/19 08:43:27 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 2467 s of XRT Photon Counting mode data and 4 UVOT
images for GRB 150819A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 42.33310, +9.80748 which is equivalent
to:

RA (J2000): 02h 49m 19.94s
Dec (J2000): +09d 48' 26.9"

with an uncertainty of 1.5 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.


GRB_name: GRB150819A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18168
SUBJECT: GRB 150819A: Swift/UVOT Upper Limits
DATE:    15/08/19 10:22:34 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld@ucl.ac.uk>

A. A. Breeveld (UCL-MSSL) and T. N. Ukwatta (LANL)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150819A 
143 s after the BAT trigger (Ukwatta et al., GCN Circ. 18163).
No optical afterglow consistent with the XRT position (Evans et al. GCN 
Circ. 18167) is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system 
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding 
chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC           143          292          147         >21.0
u_FC               301          551          246         >20.2
white              143         7062          569         >21.4
v                  631         6037          274         >19.6
b                  557         6857          274         >20.3
u                  301         6652          501         >20.4
w1                 680         6447          274         >20.0
m2                 656         6242          274         >19.9
w2                 607         7135          346         >20.4

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.22 in the direction of the 
burst (Schlegel et al. 1998).


GRB_name: GRB150819A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18169
SUBJECT: GRB 150819A: MASTER-IAC early upper limit 
DATE:    15/08/19 10:46:45 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres
The Instituto de Astrofisica de Canarias

V. Lipunov, E. Gorbovskoy,  N.Tyurina, V.Kornilov,
P.Balanutsa,A.Kuznetsov,D.Kuvshinov,
Lomonosov Moscow State University, Sternberg Astronomical Institute

K.Ivanov, O.Gres, N.M.Budnev, S.Yazev,
Irkutsk State University

D.Buckley, S. Potter, A.Kniazev, M.Kotze
South African Astronomical Observatory

A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik
Kislovodsk Solar Station of the Pulkovo Observatory

V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov, A.Gabovich
Blagoveschensk Educational State University, Blagoveschensk

V.Krushinski, I.Zalozhnih
Ural Federal University, Kourovka

Hugo Levato and Carlos Saffe
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)

Claudio Mallamaci, Carlos Lopez and Federico Podest
Observatorio Astronomico Felix Aguilar (OAFA)

MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in IAC was pointed to the  GRB150819.03 25 sec after notice time 
and 100 sec after trigger time at 2015-08-19 00:51:51 UT. On our first 
(20s exposure)  set we haven't found optical transient  within SWIFT 
error-box (Ukwatta, Barthelmy  et al., GCN 18163; Evans, GCN 18165; 
Evans et al., GCN 18167). Zenit distance was aboute ~76 degrees.
The 5-sigma upper limit has been about 17.5 mag
Our results are:

T_start     T-Tmid  Expt.   Mlimit Coadd
00:51:51.6    112     20     17.5    1
00:51:51.6    163     90     18.0    3
00:54:05.5    337    180     18.9    3
00:51:51.6    536    760     19.8   10
01:06:31.0   1995   1800     20.4   10


The message may be cited.


GRB_name: GRB150819A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18170
SUBJECT: GRB 150819A: Swift-BAT refined analysis
DATE:    15/08/19 12:37:21 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>

T. Sakamoto (AGU), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL), M. Stamatikos (OSU),
T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
 
Using the data set from T-60 to T+243 sec from the recent telemetry downlinks,
we report further analysis of BAT GRB 150819A (trigger #652643)
(Ukwatta, et al., GCN Circ. '8'63).  The BAT ground-calculated position is
RA, Dec = 42.340, 9.787 deg, which is 
   RA(J2000)  =  02h 49m 21.5s 
   Dec(J2000) = +09d 47' 11.6" 
with an uncertainty of 2.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 93%.
 
the mask-weighted light curve shows a broad peaking starting at ~T+10 sec,
peaking at ~T+40 sec, and ending at ~T+70 sec.
T90 (15-350 keV) is 52.1 +- 12.9 sec (estimated error including systematics).
 
The time-averaged spectrum from T+14.18 to T+73.46 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.72 +- 0.27.  The fluence in the 15-150 keV band is 4.8 +- 0.9 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+17.70 sec in the 15-150 keV band
is 0.3 +- 0.1 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level. 
 
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/652643/BA/


GRB_name: GRB150818A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18171
SUBJECT: GRB 150818A: MITSuME Akeno optical upper limits
DATE:    15/08/19 12:38:55 GMT
FROM:    Taketoshi Yoshii at Tokyo Tech  <yoshii.t.ac@m.titech.ac.jp>

T.Fujiwara, T. Yoshii, Y. Saito, Y. Tachibana, H. Ohuchi, Y. Yano,
S. Kurita, Y.Ono, S.Harita,Y.Muraki, Y. Yatsu, and N. Kawai (Tokyo Tech)
report on behalf of the MITSuME collaboration:

We searched for the optical counterpart of GRB 150818A (V. D'Elia et al. GCN Circular #18152) with the
optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope of Akeno Observatory, Yamanashi, Japan.

The observation started on 2015-08-18 11:54:53 UT (~18 min after the burst).
We did not find any new point source within XRT circle in all three bands.

We obtained following limits for the magnitudes.

T0+[sec]      MID-UT      T-EXP[sec]         g'           Rc           Ic
---------------------------------------------------------------------------------------
  1101     11:59:46          540           >19.4      >19.4     > 18.5
---------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used GSC2.3 catalog for flux calibration


GRB_name: GRB150819A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18172
SUBJECT: GRB 150819A: Swift-XRT refined Analysis
DATE:    15/08/19 13:02:02 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

B.P. Gompertz (U. Leicester), A. D'ai (INAF-IASFPA), A. Maselli 
(INAF-IASFPA), A. Melandri (INAF-OAB), J.A. Kennea (PSU), B. Sbarufatti
(INAF-OAB/PSU), D.N. Burrows (PSU), J.P. Osborne (U. Leicester), K.L.
Page (U. Leicester) and T.N. Ukwatta report on behalf of the Swift-XRT
team:

We have analysed 7.1 ks of XRT data for GRB 150819A (Ukwatta et al. GCN
Circ. 18163), from 122 s to 34.3 ks after the  BAT trigger. The data
comprise 43 s in Windowed Timing (WT) mode (the first 9 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Evans et
al. (GCN Circ. 18165).

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.62 (+/-0.09).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.42 (+0.24, -0.23). The
best-fitting absorption column is  6.6 (+2.3, -1.9) x 10^21 cm^-2, in
excess of the Galactic value of 1.8 x 10^21 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 6.1 x 10^-11 (7.8 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      6.6 (+2.3, -1.9) x 10^21 cm^-2
Galactic foreground: 1.8 x 10^21 cm^-2
Excess significance: 4.1 sigma
Photon index:      1.42 (+0.24, -0.23)

If the light curve continues to decay with a power-law decay index of
1.62, the count rate at T+24 hours will be 2.0 x 10^-4 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.2 x
10^-14 (1.6 x 10^-14) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00652643.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB150819A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18173
SUBJECT: GRB 150819A: RATIR Optical Observations
DATE:    15/08/19 14:08:37 GMT
FROM:    Alan M. Watson at Instituto de Astronomia UNAM  <alan@astro.unam.mx>

Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William 
H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (UCB), J. Xavier 
Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (ORAU/GSFC), 
Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), 
Jos A. de Diego (UNAM), Leonid Georgiev (UNAM), Jess Gonzlez (UNAM), 
Carlos Romn-Ziga (UNAM), Neil Gehrels (GSFC), Harvey Moseley (GSFC), 
John Capone (UMD), V. Zach Golkhou (ASU), and Vicki Toy (UMD) report:

We observed the field of GRB 150819A (Ukwatta et al., GCN 18163) with the 
Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 
1.5m Harold Johnson Telescope at the Observatorio Astronmico Nacional on 
Sierra San Pedro Mrtir from 2015/08 19.33 to 2015/08 19.48 UTC (7.08 to 
10.60 hours after the BAT trigger), obtaining a total of 2.80 hours 
exposure in the r and i bands.

For a source within the enhanced Swift-XRT error circle (Evans et al., GCN 
18165), in comparison with the USNO-B1 and 2MASS catalogs, we obtain the 
following upper limits (3-sigma):

   r > 23.60
   i > 23.91

These magnitudes are in the AB system and are not corrected for Galactic 
extinction in the direction of the GRB.

We thank the staff of the Observatorio Astronmico Nacional in San Pedro 
Mrtir.


GRB_name: GRB150818A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18174
SUBJECT: GRB 150818A: MITSuME Ishigakijima upper limits
DATE:    15/08/19 14:55:43 GMT
FROM:    Daisuke Kuroda at OAO/NAOJ  <dikuroda@oao.nao.ac.jp>

D. Kuroda (OAO, NAOJ),  H. Hanayama, T. Miyaji, J. Watanabe (IAO, NAOJ),
K. Yanagisawa (OAO, NAOJ), S.Nagayama (NAOJ), M. Yoshida (Hiroshima),
K. Ohta (Kyoto) and N. Kawai(Tokyo Tech)
report on behalf of the MITSuME and OISTER collaboration:

We observed the field of GRB 150818A (D'Elia et al., GCNC 18152)
with the optical three color (g', Rc and Ic) CCD camera attached
to the Murikabushi 1m telescope of Ishigakijima Astronomical
Observatory.

The observation started on 2015-08-18 13:09:10 UT (~1.5h after the burst).
We could not detect the previously reported afterglow
(Marshall and D'Elia, GCNC 18155; McCauley et al., GCNC 18161;
Schulze et al., GCNC 18164) in all the three bands.

Three sigma upper limits of the OT are listed below.
We used GSC2.3 catalog for flux calibration.

#T0+[day]  MID-UT    T-EXP[sec]   g'     Rc     Ic
-----------------------------------------------------
0.11943    14:28:30    6180.0   >19.4  >19.7  >19.5
-----------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]


GRB_name: GRB150818A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18175
SUBJECT: GRB 150818A: Mondy optical observations
DATE:    15/08/19 16:25:12 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

E. Mazaeva (IKI), E. Klunko (ISTP), A. Volnova (IKI), I. Korobtsev 
(ISTP),  A. Pozanenko (IKI) report on behalf of larger GRB follow-up 
collaboration:

We observed the field of Swift GRB 150818A (D'Elia et al., GCNC 18152) 
with AZT-33IK telescope of Sayan observatory (Mondy) starting on Aug., 
18 (UT) 15:07:42. We obtained several images in R-filter of 120 s 
exposure. The source previously mentioned (McCauley et al., GCN 18161; 
Schulze  et al., GCN 18164) is clearly visible. Coordinates of the 
source are (J2000) 15:21:25.56 +68:20:32.0 with uncertainty of 0.3 
arcsec in both coordinates. Preliminary photometry of the source is 
following

Date       UT start   t-T0     Filter   Exp.    OT    Err.
                       (mid, days)       (s)

2015-08-18 15:07:42   0.16843  R        31*120  20.25 0.08

Photometry is based on USNO-B1.0 stars:

USNO-B.1_id  R2
1583-0162302 16.65
1583-0162268 17.48
1583-0162214 16.71
1583-0162248 19.43

We can suggest the source as shallow fading afterglow because the source 
is significantly faded between our observations (R=20.25+/-0.08 at 4 hrs 
after burst trigger) and NOT observations at 9.62 hrs (Schulze  et al., 
GCN 18164).


GRB_name: GRB150819B
Detection_method: IPN Triangulation
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18176
SUBJECT: IPN Triangulation of GRB 150819B (short / very intense)
DATE:    15/08/19 21:52:08 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

S. Golenetskii, R. Aptekar, V. Pal'shin, D. Frederiks,
D. Svinkin, and T. Cline on behalf of the Konus-Wind team,

K. Hurley, on behalf of the IPN,

V. Connaughton, M. S. Briggs, C. Meegan, V. Pelassa,
and A. Goldstein, on behalf of the Fermi GBM team, and

A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
report:

The short-duration, very intense GRB 150819B has been detected by Fermi 
(GBM trigger 461673203 / 150819440), Konus-Wind, and INTEGRAL (SPI-ACS), 
so far, at about 37999 s UT (10:33:19).

We have triangulated it to a preliminary, 3 sigma error box whose 
coordinates are:
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
    59.386 (03h 57m 33s) +39.701 (+39d 42' 05")
  Corners:
    59.157 (03h 56m 38s) +40.372 (+40d 22' 21")
    59.671 (03h 58m 41s) +39.060 (+39d 03' 35")
    59.608 (03h 58m 26s) +39.029 (+39d 01' 45")
    59.093 (03h 56m 22s) +40.341 (+40d 20' 29")
  ---------------------------------------------
The error box area is 272 sq. arcmin, and its maximum
dimension is 1.4 deg (the minimum one is 3.4 arcmin).
The Sun distance was 81 deg.

This box may be improved.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB150819_T38000/IPN/

The time history and spectrum will be given in forthcoming GCN Circulars.


GRB_name: GRB150818A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18177
SUBJECT: GRB 150818A: 10.4m GTC spectroscopy and host galaxy
DATE:    15/08/19 22:15:53 GMT
FROM:    Alberto Castro-Tirado at Inst.de Astro. de Andalucia  <ajct@iaa.es>

R. Sanchez-Ramirez (UPV/EHU, IAA-CSIC), J. Gorosabel (+, UPV/EHU,
IAA-CSIC), D. Perez-Ramirez (+, Univ. de Jaen), S. Jeong (IAA-CSIC, SKKU),
A. J. Castro-Tirado (IAA-CSIC, ISA-UMA), F. J. Aceituno, R. Cunniffe, P.
Ferrero, Y. Hu, S. R. Oates, J. C. Tello, B.-B. Zhang (IAA-CSIC), M.
Jelinek (ASU-CAS), S. Guziy (Nikolaev Univ.), V. Sokolov (SAO-RAS), J.M.
Castro Ceron (ESAC), J. Cepa (IAC), A. Garcia (GRANTECAN) and R. Scarpa
(IAC, GRANTECAN), report:

Following the detection of GRB 150818A by Swift/BAT (D Elia et al. 2015,
GCNC 18152), we have obtained an optical spectrum (2 x 900s) with the
10.4m GTC telescope (+OSIRIS) in La Palma (Spain), starting on Aug 18,
22:05 UT (i.e. 10.5 hr postburst), covering the 3700-7800 A wavelength
range. The slit included the position of the proposed optical afterglow
(Marshall and D Elia, GCNC 18155; Schulze et al., GCNC 18164; Mazaeva et
al. GCNC 18175).

At the position of the optical afterglow, we see no obvious absorption
features with the continuum extending from 3700 to 7800 A. However we
clearly detect emission lines of [OII] 3727A, H-beta and [OIII]
4960A,5008A, all at a common redshift z = 0.282. Indeed a diffuse object
seems to be adjacent (within 1 to the west) to the optical afterglow in
the acquisition image (under 0.7 seeing), which could be the host galaxy
at the above mentioned redshift.

Further spectroscopy and monitoring at all wavelengths is encouraged to
search for the emergence of the underlying supernova component in the next
weeks.


GRB_name: GRB150819B
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18178
SUBJECT: GRB 150819B: Fermi GBM detection
DATE:    15/08/20 02:15:28 GMT
FROM:    Eric Burns at U of Alabama  <eb0016@uah.edu>

H.-F. Yu (MPE) and E. Burns (UAH)
report on behalf of the Fermi GBM Team:

"At 10:33:19.50 UT on 19 August 2015, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 150819B (trigger 461673203 / 150819440).

The on-ground calculated location, using the GBM trigger
data, is RA = 62.72, Dec = 40.60 (J2000 degrees,
equivalent to 04h 10m 53s, 40d 36'), with an uncertainty
of 2.2 degrees (radius, 1-sigma containment,
statistical only; there is additionally a systematic
error which we have characterized as a core-plus-tail model, with 90% of
GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg
systematic error. [Connaughton et al. 2015, ApJS, 216, 32] ).

The trigger resulted in an Autonomous Repoint Request (ARR)
by the GBM Flight Software owing to the high peak flux of the GRB.
This ARR was accepted and the spacecraft slewed to the GBM in-flight
location. The initial angle from the Fermi LAT boresight
to the best location is 104 degrees .

The GBM light curve consists of two pulses
with a duration (T90) of about 0.96 s (50-300 keV).
The time-averaged spectrum from T0-0.064 s to T0+0.896 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -1.04 +/- 0.02 and
the cutoff energy, parameterized as Epeak, is 532 +/- 27 keV

The event fluence (10-1000 keV) in this time interval is
(7.6 +/- 0.1)E-06 erg/cm^2. The 64-ms peak photon flux measured
starting from T0+0.000 s in the 10-1000 keV band
is 148.4 +/- 3.8 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."


GRB_name: GRB150818A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18179
SUBJECT: GRB 150818A: Continued NOT monitoring - afterglow confirmation
DATE:    15/08/20 10:59:44 GMT
FROM:    Steve Schulze at U of Iceland  <sts30@hi.is>

S. Schulze (PUC, MAS), J. P. U. Fynbo, D. Malesani (DARK/NBI), R. Tuma, S. Dinh, M. Homann, M. Munoz (NBI) and P. Jakobsson (U. Iceland) report on behalf a larger collaboration:

We observed the field of GRB 150818A (D'Elia et al., GCN 18152) with the Nordic Optical Telescope (NOT) equipped with ALFOSC. We obtained a 300-s image in R band. Observations started at 21:03 UT on August 19 (i.e. 1.39 days after the burst).

We clearly detect the source reported in Marshall et al. (GCN 18155), McCauley et al. (GCN 18161), Schulze et al. (GCN 18164) and Mazaeva et al. (GCN 18175). We measure R=21.18 +/- 0.05 calibrated against several USNO stars. The optical transient faded by 0.3 mag compared to Schulze et al. (GCN 18164) in agreement with Mazaeva et al. (GCN 18175) who also found evidence for a shallow decay. Sanchez-Ramirez (GCN 18177) hinted that the host is possibly detected in GTC image. A significant host contribution would explain the shallow decay.

[GCN OPS NOTE(20aug15):  Per author's request, the 18177 id_num for the S-R reference was added.]


GRB_name: GRB150819B
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18180
SUBJECT: Konus-Wind observation of GRB 150819B
DATE:    15/08/20 12:46:07 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

S. Golenetskii, R. Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, A. Kozlova,
and T. Cline on behalf of the Konus-Wind team, report:

The short-duration, very intense GRB 150819B
(IPN triangulation: Golenetskii et al., GCN 18176;
Fermi GBM detection: Yu and Burns, GCN 18178)
triggered Konus-Wind at T0=38000.750 s UT (10:33:20.750).

The burst light curve shows at least three separate peaks.
A total duration of the burst is  ~1.2 s.
The emission is seen up to ~3 MeV.

As observed by Konus-Wind, the burst
had a fluence of 6.61(-0.88,+1.10)x10^-6 erg/cm2,
and a 16-ms peak flux, measured from T0+0.008 s,
of 1.20(-0.17,+0.19)x10^-4 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 5 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -1.03(-0.21,+0.24)
and Ep = 348(-70,+116) keV (chi2 = 74/89 dof).
Fitting by the GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index:
beta < -2.3 (chi2 = 74/88 dof).

The spectrum near the maximum count rate
(measured from T0 to T0+0.064 s)
is best fit in the 20 keV - 5 MeV range
by a power law with exponential cutoff model
with  alpha = -0.41(-0.15,+0.17)
and Ep = 618(-86,+95) keV (chi2 = 57/43 dof).
Fitting by the GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index:
beta < -2.8 (chi2 = 57/42 dof).

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB150819_T38000/

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.


GRB_name: GRB150819A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18181
SUBJECT: GRB150819A: NOT imaging
DATE:    15/08/20 15:28:20 GMT
FROM:    Steve Schulze at U of Iceland  <sts30@hi.is>

S. Schulze (PUC, MAS), D. Malesani, J. P. U. Fynbo (DARK, NBI), J. Duus, T. Hinz-Berg, O. Busborg Jensen (NBI) and P. Jakobsson (U Iceland) report on behalf a larger collaboration:

We observed the field of GRB 150819A (Ukwatta et al., GCN 18163) with the Nordic Optical Telescope (NOT) equipped with ALFOSC. We obtained 4 images in the I band and 3 images in the z band with an individual sub-exposure time of 300 s. Observations started at 02:01 UT on August 19 (i.e. 1.19 hr after the burst).

We detect no credible source in the co-added I and z band images at the refined XRT localisation (Evans et al., GCN 18167). The limiting magnitude of the I-band image is 23 mag (3 sigma, Vega). This value is not corrected for foreground extinction. The flux calibration of the z-band image is still pending.


GRB_name: GRB150818A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18182
SUBJECT: GRB 150818A: Mondy optical observations
DATE:    15/08/20 17:24:54 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

E. Mazaeva (IKI), E. Klunko (ISTP), A. Volnova (IKI), I. Korobtsev  (ISTP), 
A. Pozanenko (IKI) report on behalf of larger GRB follow-up  collaboration:

We continue observations of  the of Swift GRB 150818A (D'Elia et al., GCNC 
18152) with AZT-33IK telescope of Sayan observatory (Mondy).   We obtained 
several images in R-filter   starting on Aug., 19 (UT) 15:33:10.  The 
optical transient (Marshall et al., GCN 18155; McCauley et al., GCN 18161; 
Schulze  et al., GCN 18164; Mazaeva et al., GCN 18175) is clearly visible. 
Preliminary photometry of the optical transient is following

Date       UT start   t-T0     Filter   Exp.    OT    Err.
                       (mid, days)       (s)

2015-08-19  15:33:10   1.18517  R        30*120  21.0 0.1

Photometry is based on USNO-B1.0 stars referenced in (Mazaeva et al., GCN 
18175)


GRB_name: GRB120422A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18183
SUBJECT: KAIT Optical Upper Limits for GRB 120422A, 120724A, 120803B, 120911A, and 120923A
DATE:    15/08/20 18:55:59 GMT
FROM:    Xiang-Gao Wang at GuangXi U  <wangxg@gxu.edu.cn>

Xianggao Wang (UC Berkeley, GXU, UNLV), WeiKang Zheng,
Alexei V. Filippenko (UC Berkeley), and S. Bradley Cenko
(GSFC) report on behalf of the KAIT GRB team:

The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, responded to Swift GRBs 120422A (Troja et al.,
GCN 13243), 120724A (D'Avanzo et al., GCN 13510), 120803B
(Racusin et al. GCN 13566), 120911A (Cannizzo et al., GCN 13744),
and 120923A (Yershov et al., GCN 13796) at 510 s, 202 s, 196 s, 147 s,
and 236 s after the burst, respectively. Observations were performed
with an automatic sequence in the clear (roughly R), V, and I filters,
and the exposure time was 20 s per image. We do not detect any new 
sources within the XRT error circles. We estimate the following upper 
limits (magnitudes) in clear-band images for each GRB calibrated to 
USNO B1.0:

GRB       Start-Time  Coadd-Images  Mid-time   Upper-Limit (3 sigma)
120422A   510 s        20 s x 6           758 s              20.6
120724A   202 s        20 s x 10         647 s              20.7
120803B   196 s        20 s x 10         644 s              21.7
120911A   147 s        20 s x 6          501 s               20.9
120923A   236 s        20 s x 6          563 s               21.0


GRB_name: GRB120729A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18184
SUBJECT: GRB 120729A: KAIT Optical Observations
DATE:    15/08/20 18:56:44 GMT
FROM:    Xiang-Gao Wang at GuangXi U  <wangxg@gxu.edu.cn>

Xianggao Wang (UC Berkeley, GXU, UNLV), WeiKang Zheng,
Alexei V. Filippenko (UC Berkeley), and S. Bradley Cenko
(GSFC) report on behalf of the KAIT GRB team:

The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, responded to Swift GRB 120729A (Ukwatta et al.,
GCN 13530) starting at 10:58:16 UT, 122 s after the burst.
Observations were performed with an automatic sequence in the
clear (roughly R), V, and I filters, and the exposure time was
20 s per image. The bright optical afterglow (Ukwatta et al. GCN 13530,
Virgili et al. GCN 13531, Oates et al. GCN 13539, Im et al. 13544,
Wren et al. 13545, Khamitov et al. GCN 13548, Gorosabel GCN 13550,
D'Avanzo et al. GCN 13551, Smith et al. GCN 13554) was detected
in all three filters. Useful observations lasted for about 2.4 hours.
Preliminary analysis shows that the afterglow decays with a single
power (with alpha = -0.87) beyond 1000 s after the burst. A light
curve is posted at
http://astro.berkeley.edu/~zwk/grb/GRB120729A/GRB120729A_kait.png .


GRB_name: GRB150821A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18186
SUBJECT: GRB 150821A: Swift detection of a burst with an optical afterglow
DATE:    15/08/21 09:59:12 GMT
FROM:    Kim Page at U.of Leicester  <klp5@leicester.ac.uk>

E. Troja (NASA/GSFC/UMCP), M. G. Bernardini (INAF-OAB),
S. B. Cenko (GSFC), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC),
P. A. Evans (U Leicester), A. Melandri (INAF-OAB) and
K. L. Page (U Leicester) report on behalf of the Swift Team:

At 09:44:00 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150821A (trigger=652847).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 341.906, -57.875 which is 
   RA(J2000) = 22h 47m 37s
   Dec(J2000) = -57d 52' 30"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multi-peaked
structure with a duration of at least 100 sec.  The peak count rate
was ~2840 counts/sec (15-350 keV), at ~35 sec after the trigger. 

The XRT began observing the field at 09:48:04.2 UT, 243.3 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 341.9129, -57.8941 which is equivalent to:
   RA(J2000)  = +22h 47m 39.10s
   Dec(J2000) = -57d 53' 38.8"
with an uncertainty of 4.9 arcseconds (radius, 90% containment). This
location is 70 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy. 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 251 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  = 22:47:39.18 = 341.91326
  DEC(J2000) = -57:53:38.1  = -57.89393
with a 90%-confidence error radius of about 0.61 arc sec. This position is 0.9
arc sec. from the center of the XRT error circle. The estimated magnitude is
16.48 with a 1-sigma error of about  0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.02. 

Burst Advocate for this burst is E. Troja (eleonora.troja AT nasa.gov). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)


GRB_name: GRB150821A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18187
SUBJECT: GRB 150821A: VLT/X-shooter redshift
DATE:    15/08/21 11:30:04 GMT
FROM:    Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst  <malesani@dark-cosmology.dk>

V. D'Elia (ASI/ASDC and INAF-OAR), T. Kruehler (ESO), K. Wiersema (U. 
Leicester), N. R. Tanvir (U. Leicester), J. Japelj (U. Ljubljana), G. 
Pugliese (API/UvA), D. Malesani (DARK/NBI), B. Milvang-Jensen 
(DARK/NBI), J. P. U. Fynbo (DARK/NBI), report on behalf of a larger 
collaboration:

We observed the optical counterpart of GRB 150821A (Troja et al., GCN 
18186) with the ESO VLT equipped with the X-shooter spectrograph. Four 
spectra with individual exposure time of 600 s were secured covering the 
wavelength range 3,000-25,000 AA. Observations were carried out in 
robotic "rapid response mode" (RRM) and spectroscopy began 12.4 min 
after the BAT trigger (7.7 min after the XRT position, at which point 
the VLT was triggered). The afterglow is well detected in our 
acquisition image, with a magnitude of R ~ 16 (11.1 min after the GRB), 
calibrated to one nearby USNO star.

We detect a number of absorption features at a common redshift of z = 
0.755, including Mg II, Mg I, Fe II, Zn II. We also detect 
fine-structure lines at the same redshift (e.g. FeII* 2396 / 2389, and 
Ni II** 2166 / 2217 / 2223), confirming that the absorption system is 
local to the GRB and not intervening.

We thank the kind assistence of the observing staff at Paranal, in 
particular Claudia Cid and Marcela Espinoza.


GRB_name: GRB150818A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18189
SUBJECT: GRB 150818A: continued Mondy optical observations
DATE:    15/08/21 15:39:24 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

E. Mazaeva (IKI), E. Klunko (ISTP), A. Volnova (IKI), I. Korobtsev 
(ISTP), A. Pozanenko (IKI) report on behalf of larger GRB follow-up 
collaboration:

We continue observations of  the of Swift GRB 150818A (D'Elia et al., 
GCNC 18152) with AZT-33IK telescope of Sayan observatory (Mondy).   We 
obtained several images in R-filter   starting on Aug., 20 (UT) 
16:54:32.  The optical transient (Marshall et al., GCN 18155; McCauley 
et al., GCN 18161; Schulze  et al., GCN 18164; Mazaeva et al., GCN 
18175) is clearly visible. Preliminary photometry of the optical 
transient is following

Date       UT start   t-T0     Filter   Exp.    OT    Err.
                       (mid, days)       (s)

2015-08-20 16:54:32   2.23334  R        15*120  21.15 0.09

Photometry is based on USNO-B1.0 stars referenced in (Mazaeva et al., 
GCN 18175).

The continued shallow decay mentioned in Schulze et al. (GCN 18179) 
indeed can be explained by underlying host galaxy (Sanchez-Ramirez et 
al., GCN 18177).


GRB_name: GRB150821A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18190
SUBJECT: GRB 150821A: Fermi GBM detection
DATE:    15/08/21 15:43:49 GMT
FROM:    Oliver Roberts at UCD/Fermi  <oliver.roberts@ucd.ie>

O.J. Roberts (UCD) reports on behalf of the Fermi GBM team:

"At 09:44:20.33 UT on August 21st 2015, the Fermi Gamma-Ray
Burst Monitor triggered and located GRB 150821A (trigger
461843064/150821406), which was also detected by Swift
(Troja et al. 2015, GCN 18186).

The trigger resulted in an Autonomous Repoint Request (ARR)
due to the high peak flux of the GRB. This ARR was accepted
and the spacecraft slewed to the GBM in-flight location. Both
the GBM in-flight and on-ground locations are consistent with
the Swift position.

The angle of the burst direction to the Fermi LAT boresight
is 57 degrees.

The GBM light curve consists of a FRED-like burst, with two
unresolved peaks and a duration of about 103 s (50-300 keV).
The time-averaged spectrum from T0-2.0s to T0+101.4s is well
fit by a Band function with Epeak = 322 +/- 18 keV,
Alpha =-1.21 +/- 0.01 and Beta = -2.27 +/- 0.10.

The event fluence (10-1000 keV) in this time interval is
(6.87 +/- 0.08)E-05 erg/cm^2. The 1.024 s peak photon flux
measured starting from T0+17.1s in the 10-1000 keV band
is 11.1 +/- 0.3 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."


GRB_name: GRB150821A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18191
SUBJECT: GRB 150821A: Enhanced Swift-XRT position
DATE:    15/08/21 16:45:25 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 910 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 150821A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 341.91332, -57.89384 which is equivalent
to:

RA (J2000): 22h 47m 39.20s
Dec (J2000): -57d 53' 37.8"

with an uncertainty of 1.8 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.


GRB_name: GRB150821A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18192
SUBJECT: GRB 150821A: Swift/UVOT Detection
DATE:    15/08/21 19:28:53 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

N. P. M. Kuin (UCL-MSSL) and E. Troja (NASA/GSFC/UMCP) report on behalf
of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150821A
251 s after the BAT trigger (Troja et al., GCN Circ. 18186).  We use the
UVOT position as reported there which is consistent with the enhanced
XRT position  (Goad et al. GCN Circ. 18191).

Preliminary detections and 3-sigma upper limits using the UVOT photometric
system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early
exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white              251          401          147         16.59 +/- 0.03
v                  560          580           20         17.21 +/- 0.18
b                  484          504           19         17.48 +/- 0.12
u                  460          479           19         16.70 +/- 0.11
w1                 435          629           39         17.62 +/- 0.18
m2                 410         7287          372        >19.8
w2                 535         1904          156         19.85 +/- 0.28

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB150819A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18193
SUBJECT: GRB 150819A: Mondy and TSHAO optical upper limits
DATE:    15/08/21 23:11:50 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

E. Mazaeva (IKI),  E. Klunko (ISTP), I. Reva (Fesenkov Astrophysical 
Institute), A. Kusakin (Fesenkov Astrophysical Institute), A. Volnova 
(IKI), I. Korobtsev (ISTP),  A. Pozanenko (IKI) report on behalf of 
larger GRB follow-up collaboration:

We observed the field of the Swift GRB 150819A (Ukwatta  et al., GCN 
18163) with AZT-33IK telescope of Sayan observatory (Mondy) and 
Zeiss-1000 (West) 1-m telescope of Tien Shan Astronomical Observatory. 
We obtained several images in R-filter in each telescope. We do not 
detect any source within enhanced XRT error circle (Evans et al., GCN 
18167).
Upper limits of the field are  following

Date       UT start   t-T0     Filter   Exp.    UL(3 sigma)  Telescope
                       (mid, days)       (s)

2015-08-19 19:06:09   0.78197  R        30*120  22.7         AZT-33IK
2015-08-19 21:57:51   0.89889  R        10*300  19.4         Zeiss-1000

Photometry is based on USNO-B1.0 stars:
USNO-B.1_id    R2
0997-0042082 17.56
0997-0042080 18.70


GRB_name: GRB150821A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18194
SUBJECT: GRB 150821A: Swift-XRT refined Analysis
DATE:    15/08/21 23:59:03 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

A. Maselli  (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo
(INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), T.G.R.
Roegiers (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester),
C. Pagani (U. Leicester) and E. Troja report on behalf of the Swift-XRT
team:

We have analysed 7.7 ks of XRT data for GRB 150821A (Troja et al. GCN
Circ. 18186), from 233 s to 40.6 ks after the  BAT trigger. The data
comprise 1.1 ks in Windowed Timing (WT) mode (the first 8 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Goad et al.
(GCN Circ. 18191).

The late-time light curve (from T0+5.9 ks) can be modelled with a
power-law decay with a decay index of alpha=1.26 (+0.15, -0.13).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.85 (+/-0.03). The
best-fitting absorption column is  1.66 (+0.09, -0.08) x 10^22 cm^-2,
at a redshift of 0.755, in addition to the Galactic value of 1.8 x
10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon
index of 2.21 (+/-0.15) and a best-fitting absorption column of 2.2
(+0.4, -0.3) x 10^22 cm^-2. The counts to observed (unabsorbed) 0.3-10
keV flux conversion factor deduced from this spectrum  is 3.7 x 10^-11
(7.1 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Galactic foreground: 1.8 x 10^20 cm^-2
Intrinsic column:    2.2 (+0.4, -0.3) x 10^22 cm^-2 at z=0.755
Photon index:      2.21 (+/-0.15)

If the light curve continues to decay with a power-law decay index of
1.26, the count rate at T+24 hours will be 8.4 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.1 x
10^-13 (6.0 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00652847.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB150821A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18195
SUBJECT: GRB 150821A: GROND afterglow observations
DATE:    15/08/22 04:11:28 GMT
FROM:    Thomas Kruehler at MPE Garching  <kruehler@mpe.mpg.de>

T. Kruehler (ESO), F. Schrey, W. Bornemann, A. Rau and J. Greiner
(all MPE)  report on behalf of a larger collaboration:

We observed the field of GRB 150821A (Swift trigger 652847;
Troja et al., GCN 18186) simultaneously in g'r'i'z'JHK
with GROND (Greiner et al. 2008, PASP 120, 405) mounted
at the 2.2 m MPG telescope at ESO La Silla Observatory (Chile).

Observations started at 02:02 UT on 2015-08-22, 16.3 hours after the
GRB trigger. For the optical afterglow (Troja et al., GCN 18186,
D'Elia et al. GCN 18187, Kuin & Troja, GCN 18192) we derive magnitudes of:

g = 23.2 +- 0.1
r = 22.6 +- 0.1
i = 22.3 +- 0.1
z = 22.0 +- 0.2

at a midtime of 17.0 hours after the trigger. This photometry is in the
AB system and calibrated against GROND zeropoints. Because GROND is 
presently being recommissioned, our measurements are preliminary.


GRB_name: GRB150821A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18196
SUBJECT: GRB 150821A, Swift-BAT refined analysis
DATE:    15/08/22 15:32:50 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

M. Stamatikos (OSU), S. D. Barthelmy (GSFC),  J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU),
E. Troja (NASA/GSFC/UMCP), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 150821A (trigger #652847)
(Troja, et al., GCN Circ. 18186).  The BAT ground-calculated position is
RA, Dec = 341.913, -57.883 deg which is
  RA(J2000)  =  22h 47m 39.0s
  Dec(J2000) = -57d -52' -58.7"
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 1.5%.

Due to the low partial coding fraction of this burst, the light curves and
burst durations are created using the special DETECTION mask aperture.
However, the spectral analysis are done using the default FLUX aperture
for more accurate results, and thus the spectral analysis is only available
after T0+174.24 s, when the burst came into the BAT calibrated field of view.
Note that the interval used for the spectral analysis included < 1% of the
total fluence.

The  mask-weighted light curve starts at ~T0+20 s and contains several
overlapping pulses. The main structure ends at ~T0+70 s, with a long-lasting
tail until ~T0+330 s. T90 (15-350 keV) is 172.1 +- 99.0 sec (estimated error
including systematics).

The time-averaged spectrum from T+174.2 to T+330.7 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.10 +- 0.37.  The fluence in the 15-150 keV band is 7.9 +- 1.9 x 10^-7 erg/cm2.
The 1-s peak spectral analysis is unavailable because the 1-s peak duration
happens before the burst came into the BAT calibrated field of view.
All the quoted errors are at the 90% confidence level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/652847/BA/


GRB_name: GRB150821A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18197
SUBJECT: GRB 150821A: LCOGT Sutherland observations
DATE:    15/08/23 11:56:57 GMT
FROM:    Cristiano Guidorzi at Ferrara U,Italy  <guidorzi@fe.infn.it>

C. Guidorzi (U. Ferrara), S. Kobayashi (LJMU), A. Gomboc (U. Ljubljana), 
C. Mundell (U. Bath) on behalf of a larger collaboration report:

The 1-m LCOGT telescopes in Sutherland (South Africa) began observing 
Swift GRB 150821A (Troja et al. GCN 18186) on August 21, 19:39 UT (~9.9 
hours after the burst trigger) with SDSS r and i filters.
At the position of the optical afterglow (Troja et al. GCN 18186; D'Elia 
et al. GCN 18187; Kuin et al. GCN 18192; Kruehler et al. GCN 18195) we 
do not detect any source down to the following limits:

Mid Time      Exposure       Filter       Magnitude
(hrs)           (s)
---------------------------------------------------
10.4           2880          r'           > 20.4
10.6           2880          i'           > 21.0
---------------------------------------------------

Calibration is done against R2 and I values of USNOB-1 nearby stars.


GRB_name: GRB150818A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18198
SUBJECT: Konus-Wind observation of GRB 150818A
DATE:    15/08/24 09:58:14 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lysenko, A. Kozlova,
and T. Cline on behalf of the Konus-Wind team, report:

The long-duration GRB 150818A (Swift-BAT trigger #652603:
D'Elia, et al., GCN Circ. 18152; Palmer, et al., GCN Circ. 18157)
was detected by Konus-Wind in the waiting mode.

The burst light curve shows a single pulse
with a total duration of about 47 s.

As observed by Konus-Wind, the burst had a fluence of
5.3(-0.6,+0.7)x10^-6 erg/cm2 and a 2.944-s peak flux,
measured from ~T0(BAT)-3.3 s, of 1.8(-0.3,+0.4)x10^-7 erg/cm2/s
(both in the 20 - 1000 keV energy range).

Modeling the K-W 3-channel time-integrated spectrum
(from T0(BAT)-6.2 s to T0(BAT)+40.9 s)
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
yields alpha = -1.4(-0.2,+0.6) and Ep = 100 (-18,+29) keV.

The K-W light curve of this burst is available at
http://www.ioffe.ru/LEA/GRBs/GRB150818A/

Assuming the redshift z=0.282 (Sanchez-Ramirez, et al., GCN 18177)
and a standard cosmology model with H_0 = 70 km/s/Mpc,
Omega_M = 0.27, and Omega_Lambda = 0.73,
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is ~1.0x10^51 erg,
the peak luminosity L_iso is ~3.6x10^49 erg/s,
and the rest-frame peak energy of the time-integrated spectrum,
Ep,i, is ~128 keV.

All the quoted errors are at 1 sigma confidence level.
All the quoted values are preliminary.


GRB_name: GRB150821A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18199
SUBJECT: GRB 150821A: LCOGT Siding Springs early observations
DATE:    15/08/24 15:29:32 GMT
FROM:    Cristiano Guidorzi at Ferrara U,Italy  <guidorzi@fe.infn.it>

C. Guidorzi (U. Ferrara), S. Kobayashi (LJMU), A. Gomboc (U. Ljubljana),
C. Mundell (U. Bath) on behalf of a larger collaboration report:

The 1-m LCOGT telescopes in Siding Springs (Australia) began observing 
Swift GRB 150821A (Troja et al. GCN 18186) on August 21, 10:22 UT (38 
minutes after the burst trigger) with SDSS r and i filters under 
initially poor sky conditions.
We detect the optical afterglow (Troja et al. GCN 18186; D'Elia et al. 
GCN 18187; Kuin et al. GCN 18192; Kruehler et al. GCN 18195) with the 
following magnitudes:

Mid Time      Exposure       Filter       Magnitude
(min)           (s)
-----------------------------------------------------
135           1680          r'           19.1 +- 0.4
233            480          r'           19.7 +- 0.3
398            720          r'           20.3 +- 0.2
-----------------------------------------------------

Calibration is done against R2 and I values of USNOB-1 nearby stars.


GRB_name: GRB150821A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18200
SUBJECT: Konus-Wind observation of GRB 150821A
DATE:    15/08/24 15:32:49 GMT
FROM:    Anna Kozlova at Ioffe Institute  <ann_kozlova@mail.ioffe.ru>

S. Golenetskii, R. Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, A. Kozlova,
and T. Cline on behalf of the Konus-Wind team, report:

The long-duration GRB 150821A (Swift-BAT trigger #652847:
Troja et al., GCN 18186; Stamatikos et al., GCN 18196;
Fermi GBM detection: Roberts, GCN 18190)
triggered Konus-Wind at T0=35074.166 s UT (09:44:34.166).

The burst light curve shows a single multi-peaked pulse
which started at ~T0-1.4 s and had a total duration of ~161.6 s.
The emission is seen up to ~10 MeV.

As observed by Konus-Wind, the burst
had a fluence of 9.16(-2.22,+2.38)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+4.768 s,
of 3.68(-1.02,+1.27)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+164.096 s)
is best fit in the 20 keV - 18 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -1.47 (-0.09,+0.15),
the high energy photon index beta = -2.21 (-7.79,+0.29),
the peak energy 350 (-125,+202) keV
(chi2 = 129/97 dof)

The spectrum near the maximum count rate
(measured from T0+0.256 to T0+8.448 s)
is best fit in the 20 keV - 18 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -1.07 (-0.10,+0.15),
the high energy photon index beta = -3.13 (-6.87,+0.80),
the peak energy 327 (-66,+58) keV
(chi2 = 91/91 dof)

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB150821_T35074/
The background variations in the soft KW band are due to solar activity.

Assuming the redshift z=0.755 (D'Elia et al., GCN 18187)
and a standard cosmology model with H_0 = 70 km/s/Mpc,
Omega_M = 0.27, and Omega_Lambda = 0.73,
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is ~1.4x10^53 erg,
the peak luminosity L_iso is ~1.0x10^52 erg/s,
and the rest-frame peak energy of the time-integrated spectrum,
Ep,i, is ~614 keV.

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.


GRB_name: GRB150824A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18201
SUBJECT: GRB 150824A: Fermi GBM detection
DATE:    15/08/24 16:04:33 GMT
FROM:    Elisabetta Bissaldi at U.Innsbruk/IAPP  <Elisabetta.Bissaldi@uibk.ac.at>

E. Bissaldi (INFN Bari) and E. Burns (UAH)
report on behalf of the Fermi GBM Team:


"At 01:53:31.76 UT on 24 August 2015, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 150824A (trigger 462074015 / 150824079).

The on-ground calculated location, using the GBM trigger
data, is

RA = 161.3
DEC = -55.9

(J2000 degrees, equivalent to 10h 45m, -55d 55'),
with an uncertainty of 1.0 degrees (radius, 1-sigma containment,
statistical only; there is additionally a systematic
error which we have characterized as a core-plus-tail model, with 90% of
GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg
systematic error. [Connaughton et al. 2015, ApJS, 216, 32] ).

The angle from the Fermi LAT boresight at the GBM trigger time is 74 degrees.

The GBM light curve consists of several peaks
with a duration (T90) of about 13 s (50-300 keV).
The time-averaged spectrum from T0 to T0+15 s is
best fit by a Band function with Epeak = 187 +/- 9 keV,
alpha = -0.77 +/- 0.03, and beta = -2.40 +/- 0.10.

The event fluence (10-1000 keV) in this time interval is
(2.03 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1 s in the 10-1000 keV band
is 22.2 +/- 0.5 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."


GRB_name: GRB150824A
Detection_method: IPN Triangulation
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18202
SUBJECT: IPN Triangulation of GRB 150824A
DATE:    15/08/25 16:29:47 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

K. Hurley, on behalf of the IPN,

I. G. Mitrofanov, D. Golovin, M. L. Litvak, and A. B. Sanin,
on behalf of the HEND-Odyssey GRB team,

S. Golenetskii, R. Aptekar, V. Pal'shin, D. Frederiks,
D. Svinkin, and T. Cline on behalf of the Konus-Wind team,

V. Connaughton, M. S. Briggs, C. Meegan, V. Pelassa,
and A. Goldstein, on behalf of the Fermi GBM team,

A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
and

W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr,
on behalf of the GRS-Odyssey GRB team, report:

The long-duration, bright GRB 150824A has been detected by Fermi (GBM: 
Bissaldi and Burns, GCN Circ. 18201), Konus-Wind, INTEGRAL (SPI-ACS), 
and Mars-Odyssey (HEND), so far, at about 6812 s UT (01:53:32).

We have triangulated it to a preliminary, 3 sigma error box whose 
coordinates are:
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   167.550 (11h 10m 12s) -56.964 (-56d 57' 49")
  Corners:
   166.891 (11h 07m 34s) -57.136 (-57d 08' 10")
   167.182 (11h 08m 44s) -57.159 (-57d 09' 31")
   168.205 (11h 12m 49s) -56.787 (-56d 47' 12")
   167.915 (11h 11m 40s) -56.767 (-56d 46' 03")
  ---------------------------------------------
The error box area is 253 sq. arcmin, and its maximum
dimension is 48 arcmin (the minimum one is 6.2 arcmin).
The Sun distance was 69 deg.

This box may be improved.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB150824_T06810/IPN/

The Konus-Wind time history and spectrum will be given in a forthcoming 
GCN Circular.


GRB_name: GRB150824A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18203
SUBJECT: Konus-Wind observation of GRB 150824A
DATE:    15/08/25 16:37:18 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred@mail.ioffe.ru>

S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lysenko, A. Kozlova, and T. Cline
on behalf of the Konus-Wind team, report:

The long-duration, bright GRB 150824A
(Fermi-GBM detection: Bissaldi & Burns, GCN 18201;
IPN triangulation: Hurley et al., GCN 18202)
triggered Konus-Wind at T0=6810.119 s UT (01:53:30.119).

The light curve shows several pulses in the interval
from ~T0-0.5 s to ~T0+15 s.
The emission is seen up to ~5 MeV.

As observed by Konus-Wind, the burst had a fluence
of 1.8(-0.2,+0.2)x10^-5 erg/cm2, and a 64-ms peak flux,
measured from T0+0.896 s, of 7.6(-0.8,+0.9)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum (measured from T0 to T0+16.384 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.96 (-0.16,+0.11),
the high energy photon index beta = -3.11 (-6.89,+0.44),
the peak energy Ep = 197 (-16,+22) keV,
chi2 = 106/97 dof.

The spectrum near the peak count rate (measured from T0 to T0+8.192 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.83 (-0.11,+0.12),
the high energy photon index beta = -2.79 (-0.56,+0.29),
the peak energy Ep = 200 (-19,+20) keV,
chi2 = 90/92 dof.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB150824_T06810/

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.


GRB_name: GRB150818A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18205
SUBJECT: GRB 150818A: possible SN rise in light curve of Mondy observations
DATE:    15/08/27 16:54:50 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

E. Mazaeva (IKI), E. Klunko (ISTP), A. Volnova (IKI), I. Korobtsev 
(ISTP), A. Pozanenko (IKI) report on behalf of larger GRB follow-up 
collaboration:

We continue observations of the Swift GRB 150818A (D'Elia et al., GCN 
18152) with AZT-33IK telescope of Sayan observatory (Mondy).   We 
imaged optical transient (Marshall et al., GCN 18155; McCauley et al., 
GCN 18161; Schulze et al., GCN 18164; Mazaeva et al., GCN 18175)  in 
R-filter on Aug., 21, 22, 23, and 26.  The optical transient is clearly 
visible in each epochs. Preliminary light curve of the optical transient 
can be found in

http://grb.rssi.ru/GRB150818A/GRB150818A_R_lc.png

(Photometry is based on USNO-B1.0 stars referenced in (Mazaeva et al., 
GCN 18175).

One can suggest that steady re-brightening of the optical transient is 
related to a Supernova associated with nearby GRB 150818A  (z = 0.282, 
Sanchez-Ramirez et al., GCN 18177). We encourage observation for 
spectroscopic SN-confirmation.


GRB_name: GRB150831A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18209
SUBJECT: GRB 150831A: Swift detection of a short burst
DATE:    15/08/31 10:51:14 GMT
FROM:    Jamie A. Kennea at PSU/Swift-XRT  <kennea@swift.psu.edu>

A. Y. Lien (GSFC/UMBC), D. N. Burrows (PSU) and J. A. Kennea (PSU)
report on behalf of the Swift Team:

At 10:34:12 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150831A (trigger=653838).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 221.023, -25.649 which is 
   RA(J2000) = 14h 44m 05s
   Dec(J2000) = -25d 38' 57"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a short pulse
with a duration of about 1.2 sec.  The peak count rate
was ~10000 counts/sec (15-350 keV), at ~ 0.1 sec after the trigger. 

The XRT began observing the field at 10:35:36.3 UT, 83.4 seconds after
the BAT trigger. Using promptly downlinked data we find a bright, fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 221.0245,
-25.6356 which is equivalent to:
   RA(J2000)  = 14h 44m 05.87s
   Dec(J2000) = -25d 38' 08.2"
with an uncertainty of 2.6 arcseconds (radius, 90% containment). This
location is 48 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper.  

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 1.14
x 10^21 cm^-2 (Willingale et al. 2013). 

The initial flux in the 2.5 s image was 8.91e-10 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 88 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
The 8'x8' region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.11. 

Burst Advocate for this burst is A. Y. Lien (amy.y.lien AT nasa.gov). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)


GRB_name: GRB150831A
Detection_method: INTEGRAL
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18210
SUBJECT: INTEGRAL detection of GRB 150831A
DATE:    15/08/31 11:41:33 GMT
FROM:    Sandro Mereghetti at IASF/CNR  <sandro@iasf-milano.inaf.it>

S.Mereghetti (IASF-Milano), D.Gotz (CEA, Saclay), C.Ferrigno, E.Bozzo, 
L.Ducci (ISDC, Versoix), and J.Borkowski (CAMK, Torun) on behalf of the 
IBAS Localization Team report:

GRB 150831A (Lien et al. GCN 18209) has been detected by IBAS in the 
IBIS/ISGRI data with a significance slightly below the threshold for 
automatic alert delivery (IBAS Weak Alert n.7228 was distributed at 
10:34:24 UT).

The burst consists of a single peak with duration of 2 s and starting at 
10:34:12 UT.

The IBIS/ISGRI refined coordinates (J2000) are:

R.A.= 221.0207 deg
DEC.= -25.6474 deg

with an uncertainty of 3   arcmin (90% c.l.).

The burst had a fluence of about 3x10e-7 erg/cm2 in the the 20-200 keV 
energy range.

A plot of the light curve will  be posted at
http://ibas.iasf-milano.inaf.it/IBAS_Results.html


GRB_name: GRB150831A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18211
SUBJECT: GRB 150831A: optical upper limit ISON-SSO
DATE:    15/08/31 13:02:17 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

L. Elenin (KIAM), A. Volnova (IKI), E. Mazaeva (IKI), I. Molotov (KIAM), 
A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:

We observed the field of Swift and INTEGRAL short GRB 150309A (Lien et 
al., GCN 18209; Mereghetti et al., GCN 18210) with with 0.4-m f/2.4 
telescope of ISON-SSO (Siding Spring Observatory) starting on Aug. 31 
(UT) 10:44:10 (i.e. 10 minutes after burst trigger). We obtained 30 
unfiltered images of 30 s exposure. We do not detect any optical source 
within XRT error circle (Lien et al., GCN 18209). Preliminary photometry 
of the filed is following


Date       UT start   t-T0     Filter   Exp.   UL (3 sigma)
                       (mid, days)       (s)

2015-08-31 10:44:10   0.01299  none    30*30   18.8


Photometry is based on nearby USNO-B1.0 stars (R2)


GRB_name: GRB150831A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18212
SUBJECT: GRB 150831A: Enhanced Swift-XRT position
DATE:    15/08/31 16:33:51 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 1089 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 150831A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 221.02422, -25.63499 which is equivalent
to:

RA (J2000): 14h 44m 5.81s
Dec (J2000): -25d 38' 06.0"

with an uncertainty of 1.7 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.


GRB_name: GRB150818A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18213
SUBJECT: GRB 150818A: Spectroscopic confirmation of the SN from GTC
DATE:    15/08/31 17:49:21 GMT
FROM:    Antonio de Ugarte Postigo at IAA-CSIC  <deugarte@iaa.es>

A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), Z. Cano (U. Iceland), 
D. A. Perley (DARK/NBI), S. Schulze (PUC, MAS), D. Xu (NAOC/CAS), 
R. Sanchez-Ramirez (IAA-CSIC), D. Malesani (DARK/NBI), G. Lombardi 
(GRANTECAN, IAC, ULL), and A. Garcia (GRANTECAN), R. Scarpa 
(GRANTECAN) report on behalf of a larger collaboration:

We observed the counterpart of GRB 150818A (D'Elia et al. GCN 18152; 
Marshall et al. GCN 18155; McCauley et al. GCN 18161; Mazaeva et al. 
GCN 18175; Sanchez-Ramirez et al. GCN 18177; Mazaeva et al. GCN 
18182, GCN 18189, GCN 18205; Schulze et al. GCN 18179) with the 
10.4 m GTC telescope (+OSIRIS) on the 29th August 2015 (11.4 days 
after the burst). The observation consisted of 3x900 s spectroscopy using 
the R1000B grism (3700-7800 AA coverage with a resolution of ~1000) 
plus g-, r- and i-band imaging. We detect a point-like source at the location 
of the afterglow superposed on top of an extended source. 

The combined spectrum shows broad features typical of a broad-lined 
Type Ic SN near maximum light, thus confirming the detection of a rising 
supernova proposed by Mazaeva et al. (GCN 18205). The spectrum also 
shows narrow emission features of [OII], [OIII] and H-beta at z=0.282 
(Sanchez-Ramirez et al. GCN 18177).


GRB_name: GRB150831A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18214
SUBJECT: GRB 150831A: Swift-BAT refined analysis
DATE:    15/08/31 19:08:41 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), J. Norris (BSU), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU), (i.e. the Swift-BAT team):

Using the data set from T-240 to T+938 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 150831A (trigger #653838)
(Lien, et al., GCN Circ. 18209).  The BAT ground-calculated position is
RA, Dec = 221.034, -25.619 deg which is
  RA(J2000)  =  14h 44m 08.1s
  Dec(J2000) = -25d 37' 08.4"
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 52%.

The mask-weighted light curve shows a short pulse that starts and peaks
at ~ T0, and ends at ~ T+1.4 s. T90 (15-350 keV) is 1.15 +- 0.23 sec
(estimated error including systematics).

The time-averaged spectrum from T-0.03 to T+1.40 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
0.81 +- 0.16.  The fluence in the 15-150 keV band is 3.8 +- 0.3 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.0 sec in the 15-150 keV band
is 3.4 +- 0.3 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

The lag analysis using 8-ms binned light curve gives a spectral lag
of -2 ms +-  5 ms for the 100-350 keV and 25-50 keV band,
and 13 ms +- 20 ms for the 50-100 keV and 15-25 keV band.
These values are consistent with short GRBs.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/653838/BA/


GRB_name: GRB150831B
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18215
SUBJECT: GRB 150831B: Swift detection of a probable burst
DATE:    15/08/31 22:34:04 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

F. E. Marshall (NASA/GSFC), S. D. Barthelmy (GSFC),
A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL) and T. Sakamoto (AGU)
report on behalf of the Swift Team:

At 22:19:27 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150831B (trigger=653978).  Swift did not slew due to observing
constraint.  The BAT on-board calculated location is 
RA, Dec 271.021, -27.252, which is 
   RA(J2000)  =  18h 04m 05s
   Dec(J2000) = -27d 15' 07"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a couple of overlapping peaks
structure with a total duration of about 3 sec.  The peak count rate
was ~2000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

Due to an observing constraint, Swift will not slew until T0+49.6
minutes. There will be no XRT or UVOT data until this time. 

We note that this source is in the projected direction of the 
Galactic bulge (lon,lat = 3.51,-2.66) and for that reason there 
is a strong possibility that this is a Galactic source.  However, its
light curve and the presence of flux above 100 keV are more consistent 
with a cosmological GRB. 

Determination of the nature of this event will require XRT observations
and the full downlinked dataset. 

Burst Advocate for this burst is F. E. Marshall (marshall AT milkyway.gsfc.nasa.gov). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)


GRB_name: GRB150831A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18216
SUBJECT: GRB 150831A: Swift-XRT refined Analysis
DATE:    15/08/31 22:51:03 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), D.N. Burrows (PSU),
T.G.R. Roegiers (PSU), L.M. McCauley (PSU), K.L. Page (U. Leicester),
C. Pagani (U. Leicester), A.P. Beardmore (U. Leicester), V. D'Elia
(ASDC) and A.Y. Lien report on behalf of the Swift-XRT team:

We have analysed 8.6 ks of XRT data for GRB 150831A (Lien et al. GCN
Circ. 18209), from 72 s to 22.5 ks after the  BAT trigger. The data
comprise 8 s in Windowed Timing (WT) mode (taken while Swift was
slewing), with the remainder in Photon Counting (PC) mode. The enhanced
XRT position for this burst was given by Osborne et al. (GCN Circ.
18212).

The light curve can be modelled with a power-law decay with a decay
index of alpha=2.52 (+0.21, -0.22).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.25 (+0.17, -0.12). The
best-fitting absorption column is  1.27 (+0.89, -0.13) x 10^21 cm^-2,
consistent with the Galactic value of 1.1 x 10^21 cm^-2 (Willingale et
al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux
conversion factor deduced from this spectrum  is 5.0 x 10^-11 (5.4 x
10^-11) erg cm^-2 count^-1. 

A summary of the WT-mode spectrum is thus:
Total column:      1.27 (+0.89, -0.13) x 10^21 cm^-2
Galactic foreground: 1.1 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:      1.25 (+0.17, -0.12)

If the light curve continues to decay with a power-law decay index of
2.52, the count rate at T+24 hours will be 2.1 x 10^-7 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.1 x
10^-17 (1.2 x 10^-17) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00653838.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB150831B
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18217
SUBJECT: GRB 150831B: Swift-XRT observations
DATE:    15/08/31 23:37:00 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), D.N. Burrows
(PSU), J.A. Kennea (PSU), S. Campana (INAF-OAB) and G. Cusumano
(INAF-IASF PA) report on behalf of the Swift-XRT team:

The XRT began observing the field of GRB 150831B at 23:10:52.8 UT,
3085.5 seconds after the BAT trigger. Using promptly downlinked data we
find an uncatalogued X-ray source located at RA, Dec 271.03936,
-27.25933 which is equivalent to:
   RA(J2000)  = 18h 04m 09.45s
   Dec(J2000) = -27d 15' 33.6"
with an uncertainty of 3.9 arcseconds (radius, 90% containment). This
location is 64 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper.  We
cannot determine whether the source is fading at the present time. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 5.13
x 10^21 cm^-2 (Willingale et al. 2013). 


GRB_name: GRB150831A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18218
SUBJECT: GRB 150831A: Swift/UVOT Upper Limits
DATE:    15/09/01 00:14:09 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <siegel@swift.psu.edu>

M. H. Siegel (PSU) and A. Y. Lien (GSFC/UMBC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150831A
88 s after the BAT trigger (Lien et al., GCN Circ. 18209).
No optical afterglow consistent with the XRT position
(Osborne et al. GCN Circ. 18212)
is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC            88          238          147         >20.5
u_FC               300          550          246         >19.9
white               88         6622          746         >21.2
v                  631        17885         1356         >19.8
b                  557         6417          452         >20.4
u                  300        12784         1326         >21.0
w1                 680        12112         1153         >21.3
m2                 655        18529         1750         >21.3
w2                 607        16972         1357         >21.1

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.11 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB150831A
Detection_method: GROND
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18219
SUBJECT: GRB 150831A: GROND Upper Limits
DATE:    15/09/01 03:00:06 GMT
FROM:    Fabian Knust at MPE/GROND  <fknust@mpe.mpg.de>

F. Knust (MPE Garching), S. Klose (TLS Tautenburg), and J. Greiner (MPE Garching) report on behalf of the GROND team: 
We observed the field of GRB 150831A (Swift trigger 653838; Lien et al., GCN #18209) simultaneously in g'r'i'z'JHK 
with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla Observatory (Chile). 
Observations started at 23:21UT on 2015-08-31, 13hrs after the GRB trigger. They were performed at
an average seeing of 2.4" and at an average airmass of 1.5. 

We do not detect a source within the Swift-XRT error circle reported by Osborne et al. (GCN #18212) down to 
g'> 24.9 mag, 
r'> 24.5 mag, 
i'> 23.8 mag, 
z'> 23.8 mag, 
J> 21.4 mag, 
H> 20.9 mag, and 
K> 18.6 mag. 

The given limits are derived based on calibrating the images against GROND zeropoints as well as 2MASS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=0.1 mag in the direction of the burst (Schlegel et al. 1998).             


GRB_name: GRB150831B
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18220
SUBJECT: GRB 150831B: Fermi GBM detection
DATE:    15/09/01 04:53:10 GMT
FROM:    Peter Veres at ELTE,Budapest  <veresp@gmail.com>

P. Veres (UAH) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 22:19:27.158 UT on 31 August 2015, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 150831B (trigger 462752371 / 150831930)
which was also detected by the Swift/BAT and XRT
(Marshall et al. 2015, GCN 18215 and Evans et al. 2015, GCN 18217)
The GBM on-ground location is consistent with the Swift position.


The angle from the Fermi LAT boresight at the GBM trigger time is 96
degrees.


The GBM light curve has a duration (T90) of about 13.8 s (50-300 keV).
The time-averaged spectrum from T0-4.0 s to T0+6.3 s is
adequately fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.93 +/- 0.12 and
the cutoff energy, parameterized as Epeak, is 82.3 +/- 5.5 keV.


The event fluence (10-1000 keV) in this time interval is
(2.51 +/- 0.11)E-6 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+0.1 s in the 10-1000 keV band
is 9.1 +/- 0.4 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."


GRB_name: GRB150831B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18221
SUBJECT: GRB 150831B: MASTER-IAC early optical observations 
DATE:    15/09/01 07:28:29 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres
The Instituto de Astrofisica de Canarias

V. Lipunov, E. Gorbovskoy,  N.Tyurina, V.Kornilov,
P.Balanutsa, A.Kuznetsov, D.Kuvshinov, E.Popova
Lomonosov Moscow State University, Sternberg Astronomical Institute

K.Ivanov, O.Gres, N.M.Budnev, S.Yazev,
Irkutsk State University

D.Buckley, S. Potter, A.Kniazev, M.Kotze
South African Astronomical Observatory

A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik
Kislovodsk Solar Station of the Pulkovo Observatory

V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov, A.Gabovich
Blagoveschensk Educational State University, Blagoveschensk

V.Krushinski, I.Zalozhnih
Ural Federal University, Kourovka

Hugo Levato and Carlos Saffe
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)

Claudio Mallamaci, Carlos Lopez and Federico Podest
Observatorio Astronomico Felix Aguilar (OAFA)

MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru; 
http://161.72.133.2/) 
located in IAC was pointed to the  GRB150831B 24 sec after notice time 
and 56 sec after trigger time at 2015-08-31 22:20:23 UT (Swift: Marshall 
et al., GCN 18215; and Fermi:  Veres and C. Meegan, GCN 18220) .
On our first (10s exposure)  set (two polarisations) we  did  not found 
optical transient 
within SWIFT  error-box  (Marshall et al., GCN 18215; Evans et al., GCN 
18217) brighter then 16.3. The observations were stoped by beautifull 
Canarian sun rise ( see 
http://observ.pereplet.ru/images/webcam01spt2015.jpg ) at 2015-09-01 
06:37:36 UT.


Pro.type Date time + -      Exp.time Limit Filt. Tube.
                    Start
Alert      2015-08-31 22:20:23    10 16.3 P WEST
Alert     2015-08-31 22:20:23         10 15.6 P EAST
Alert     2015-08-31 22:21:07         20 16.4 P WEST
Alert     2015-08-31 22:21:07         20 15.9 P EAST
Alert     2015-08-31 22:21:37         30 16.8 P WEST
Alert     2015-08-31 22:21:37         30 16.2 P EAST
Alert     2015-08-31 22:22:18         30 0.0* P WEST 
Alert     2015-08-31 22:22:18         30 16.2 P EAST
Alert     2015-08-31 22:22:57         40 16.9 P WEST
Alert     2015-08-31 22:22:57         40 16.3 P EAST
Alert     2015-08-31 22:23:47         50 17.0 P WEST
Alert     2015-08-31 22:23:47         50 16.5 P EAST
Alert     2015-08-31 22:24:47         60 17.0 P WEST
Alert     2015-08-31 22:24:47         60 16.5 P EAST
Alert     2015-08-31 22:25:56         80 17.2 P WEST
Alert     2015-08-31 22:25:56         80 16.6 P EAST
Alert     2015-08-31 22:27:26         100 17.2 P WEST
Alert     2015-08-31 22:27:26         100 16.6 P EAST
Alert     2015-08-31 22:29:17         120 17.3 P WEST
Alert     2015-08-31 22:29:17          120 16.6 P EAST
Alert     2015-08-31 22:31:27         140 17.3 P WEST
Alert     2015-08-31 22:31:27         140 16.7 P EAST
Alert     2015-08-31 22:33:57         170 17.3 P WEST
Alert     2015-08-31 22:33:57         170 16.7 P EAST

* - no stars 
Our server hase a lot of job in Milky Way star dust now.

This message may be cited.


GRB_name: GRB150831B
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18222
SUBJECT: GRB 150831B: Swift-XRT refined Analysis
DATE:    15/09/01 10:58:46 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P. D'Avanzo (INAF-OAB), T.G.R. Roegiers (PSU), L.M. McCauley (PSU),
J.A. Kennea (PSU), C. Pagani (U. Leicester), A.P. Beardmore (U.
Leicester), V. D'Elia (ASDC), A. D'ai (INAF-IASFPA) and F. E. Marshall
(NASA/GSFC) report on behalf of the Swift-XRT team:

We have analysed 3.8 ks of XRT data for GRB 150831B (Marshall et al.
GCN Circ. 18215), from 3.1 ks to 28.3 ks after the  BAT trigger. The
data are entirely in Photon Counting (PC) mode. The refined XRT
position is RA, Dec = 271.0396, -27.2590 which is equivalent to:

RA (J2000): 18 04 09.49
Dec(J2000): -27 15 32.4

with an uncertainty of 3.7 arcsec (radius, 90% confidence).

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.32 (+0.26, -0.21).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.5 (+0.7, -0.6). The
best-fitting absorption column is  1.7 (+1.0, -0.7) x 10^22 cm^-2, in
excess of the Galactic value of 5.1 x 10^21 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 4.4 x 10^-11 (1.6 x 10^-10) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      1.7 (+1.0, -0.7) x 10^22 cm^-2
Galactic foreground: 5.1 x 10^21 cm^-2
Excess significance: 2.9 sigma
Photon index:      2.5 (+0.7, -0.6)

If the light curve continues to decay with a power-law decay index of
1.32, the count rate at T+24 hours will be 1.7 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.6 x
10^-14 (2.7 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00653978.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB150831B
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18223
SUBJECT: GRB 150831B: Swift-BAT refined analysis
DATE:    15/09/01 13:21:00 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>

S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
F. E. Marshall (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
 
Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 150831B (trigger #653978)
(Marshall et al., GCN Circ. 18215).  The BAT ground-calculated position is
RA, Dec = 271.030, -27.243 deg, which is 
   RA(J2000)  =  18h 04m 07.2s 
   Dec(J2000) = -27d 14' 34.4" 
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 7%.
 
The mask-weighted light curve shows two peaks starting at ~T-0.5 sec,
peaking at ~T+1 sec, and ending at ~T+8 sec.  T90 (15-350 keV)
is 6.2 +- 1.0 sec (estimated error including systematics).
 
The time-averaged spectrum from T-0.58 to T+6.84 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.87 +- 0.19.  The fluence in the 15-150 keV band is 1.4 +- 0.2 x 10^-06 erg/cm2.
The 1-sec peak photon flux measured from T-0.15 sec in the 15-150 keV band
is 6.1 +- 1.1 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level. 

In the BAT energy band, the hardness ratio vs T90 is typical of a GRB origin,
but not inconsistant with a galactic origin.  The T90 is too long for a
magnetar origin. We also note that the fading in the X-ray band is tyical
for a GRB (D'Avanzo, GCN 18222).
 
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/653978/BA/


GRB_name: GRB150821A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18224
SUBJECT: GRB 150821A: Flattening in the UVOT light curve
DATE:    15/09/01 15:33:59 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

Paul Kuin, Massimiliano de Pasquale (UCL/MSSL), Daniele
Malesani (DARK/NBI) and Peter Brown (TAMU) report on
behalf of the Swift UVOT team:

The light curve from GRB 150821A as observed by Swift/UVOT has
been monitored continuously since its discovery, up to about
300 ks in all seven filters, and in u, v and white since.

The GRB brightness decreased as a straight power law with
index -1.32 (+0.06/-0.05) until about 10 ks. At 100 ks
there was a clear flattening in the light curve, and around
250 ks a slight brightening may have taken place, but the
brightness could also be flat within our observational errors.
Data taken at 835 ks are consistent with a flat or slightly
decreasing brightness.

The summed 5 ks image in the white band from 300 - 800 ks
shows a nearby extended object to the north-west with
white = 22.01 +/- 0.17 mag, slightly brighter than the GRB at
about 10" distance which currently is at white=23.2 +/- 0.7
magnitudes, and is located about 5" from the edge of the
nearby object.

At this time it is unclear whether the observed flattening is
due to the host galaxy (hosts at this distance have typically
a size of 1" only) or are the emergence of a supernova
contribution to the afterglow. At the redshift of z = 0.755
(D'Elia et al., GCN Circ. 18187), the observed brightness
would imply a SN significantly brighter than those typically
associated with GRBs.

Further ground observations are encouraged.


GRB_name: GRB150901A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18225
SUBJECT: GRB 150901A: Swift detection of a burst
DATE:    15/09/01 15:40:23 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

B. Sbarufatti (INAF-OAB/PSU), S. D. Barthelmy (GSFC),
J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA) and
T. N. Ukwatta (LANL) report on behalf of the Swift Team:

At 15:26:35 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150901A (trigger=654042).  Swift did not slew due Sun observing
constraint.  The BAT on-board calculated location is 
RA, Dec 183.586, +25.038, which is 
   RA(J2000)  =  12h 14m 21s
   Dec(J2000) = +25d 02' 19"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single peak
with a duration of about 25 sec.  The peak count rate
was ~700 counts/sec (15-350 keV), at ~1 sec after the trigger. 

Due to a Sun observing constraint, Swift cannot slew to the BAT
position until 00:01 UT on 2015 October 28. There will thus be no XRT
or UVOT data for this trigger before this time. 

Burst Advocate for this burst is B. Sbarufatti (boris.sbarufatti AT brera.inaf.it). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)


GRB_name: GRB150831A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18226
SUBJECT: Konus-Wind observation of GRB 150831A
DATE:    15/09/01 15:51:15 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lysenko, A. Kozlova,
and T. Cline on behalf of the Konus-Wind team, report:

The short-duration GRB 150831A (Swift trigger 648437:
Lien, et al., GCN Circ. 18209; Ukwatta, et al., GCN Circ. 18214;
INTEGRAL detection: Mereghetti et al., GCN Circ. 18210)
triggered Konus-Wind at T0=38049.519 s UT (10:34:09.519).

The burst light curve shows a short pulse with
a total duration of ~1 s.

As observed by Konus-Wind, the burst had a fluence of
(2.4 +/- 0.4)x10^-6 erg/cm2, and a 16-ms peak flux,
measured from T0-0.082 s, of (9.1 +/- 2.5)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

Since the most intense part of the burst was detected before
the trigger, the spectral analysis was performed using
the KW 3-channel light curve data.

Modeling the 3-channel time-integrated spectrum
(from T0-0.108 s to T0+0.912 s) by a power law
with exponential cutoff (CPL) model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
yields alpha = -0.5 +/- 0.3, and Ep = 564 +/- 122 keV.

The K-W light curve of this burst is available at
http://www.ioffe.rssi.ru/LEA/GRBs/GRB150831_T38049/

All the quoted errors are estimated at the 1 sigma confidence level.
All the presented results are preliminary.


GRB_name: GRB150831B
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18227
SUBJECT: GRB 150831B: Swift/UVOT Upper Limits
DATE:    15/09/01 20:59:18 GMT
FROM:    Frank Marshall at GSFC  <femarsha@khamseen.gsfc.nasa.gov>

F. E. Marshall (NASA/GSFC) reports on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150831B
3089 s after the BAT trigger (Marshall et al., GCN Circ. 18215).
No optical afterglow consistent with the refined XRT position
(D'Avanzo et al., GCN Circ. 18222) is detected in the initial UVOT 
exposures. We note that this is a very crowded field.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC          3089         3239          147         >20.6
v                 3246         3445          197         >18.2
b                 8838         9745          885         >20.3
u                 3861         5659          158         >19.4
w1                3656         3856          197         >19.2
m2                3451         3651          197         >20.2

The magnitudes in the table are not corrected for the large
Galactic extinction in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB150902A
Detection_method: Fermi LAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18228
SUBJECT: GRB 150902A: Fermi-LAT detection
DATE:    15/09/03 07:19:06 GMT
FROM:    Magnus Axelsson at Stockholm U.  <magaxe@kth.se>

GRB 150902A: Fermi-LAT detection

M. Arimoto (Tokyo Tech), M. Axelsson (KTH Stockholm), J. Racusin (NASA/GSFC), E. Bissaldi (INFN Bari),
D. Kocevski (NASA/GSFC) report on behalf of the Fermi-LAT team:

At 17:35:39.37 UT on 2015-09-02, Fermi-LAT detected high-energy emission from GRB 150902A,
which was also detected by Fermi-GBM (trigger 462908143/150902733).

The best LAT on-ground location is found to be

RA, Dec = 214.926, -69.361 degrees (J2000)

with an error radius of 0.127 deg (90% containment, systematic error only). This was 38 deg
from the LAT boresight at the time of the trigger and triggered an autonomous repoint of the
spacecraft.

The data from the Fermi-LAT show a significant increase in the event rate that is spatially and
temporally correlated with the GBM emission. More than 50 photons above 100 MeV and 9
photons above 1 GeV were observed within 300 seconds. The highest-energy photon is a 11 GeV
event which is observed ~100 seconds after the GBM trigger.

A Swift ToO has been requested for this burst.

The Fermi-LAT point of contact for this burst is Daniel Kocevski (daniel.kocevski@nasa.gov<mailto:daniel.kocevski@nasa.gov>).

The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV
to greater than 300 GeV. It is the product of an international collaboration between NASA and
DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.


GRB_name: GRB150902A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18229
SUBJECT: GRB 150902A: Fermi GBM detection
DATE:    15/09/03 09:32:09 GMT
FROM:    Oliver Roberts at UCD/Fermi  <oliver.roberts@ucd.ie>

O.J. Roberts (UCD) and G. Younes (GWU) report on behalf
of the Fermi GBM team:

"At 17:35:39 UT on September 2nd 2015, the Fermi
Gamma-Ray Burst Monitor triggered and located
GRB 150902A (trigger 462908143/150902733), which was
also detected by Fermi-LAT (Axelsson et al. 2015, GCN 18228).

The trigger resulted in an Autonomous Repoint Request (ARR)
by the GBM Flight Software due to the high peak flux of the
GRB. This ARR was accepted and the spacecraft slewed to the
GBM in-flight location. Both the GBM in-flight and on-ground
locations are consistent with the LAT position.

The GBM light curve consists of a series of unresolved pulses,
with a duration of about 14 s (50-300 keV). The time-averaged
spectrum from T0+3.0s to T0+17.0s is well fit by a Band
function with Epeak = 351.40 +/- 5.61 keV, Alpha =-0.48 +/- 0.02
and Beta = -2.32 +/- 0.03.

The event fluence (10-1000 keV) in this time interval is
(8.221 +/- 0.043)E-05 erg/cm^2. The 1.024 s peak photon flux
measured starting from T0+8.8s in the 10-1000 keV band is
61.9 +/- 0.5 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."


GRB_name: GRB150902A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18230
SUBJECT: GRB 150902A: Swift ToO observations
DATE:    15/09/03 10:17:16 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a ToO observation of the Fermi/LAT GRB 150902A. 
Automated analysis of the XRT data will be presented online at
http://www.swift.ac.uk/ToO_GRBs/00020549

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the Fermi/LAT event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a 
GCN Circular after manual consideration.

Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).

This circular is an official product of the Swift-XRT team.


GRB_name: GRB150901A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18232
SUBJECT: GRB 150901A, Swift-BAT refined analysis
DATE:    15/09/03 12:53:33 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU), B. Sbarufatti (INAF-OAB/PSU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

Using the data set from T-254 to T+640 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 150901A (trigger #654042)
(Sbarufatti, et al., GCN Circ. 18225).  The BAT ground-calculated position is
RA, Dec = 183.609, 25.076 deg which is
  RA(J2000)  =  12h 14m 26.1s
  Dec(J2000) = +25d 04' 35.2"
with an uncertainty of 2.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 41%.

The mask-weighted light curve shows some weak emissions that start at
~ T-70 s, followed by the main structure with several overlapping pulses
from ~T0 to ~T+18 s. T90 (15-350 keV) is 64.0 +- 35.8 sec (estimated error
including systematics).

The time-averaged spectrum from T-61.8 to T+18.2 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.72 +- 0.53.  The fluence in the 15-150 keV band is 4.5 +- 1.3 x 10^-7 erg/cm2.
The 1-s peak photon flux is unconstrained due to the weakness of the burst.
All the quoted errors are at the 90% confidence level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/654042/BA/


GRB_name: GRB150902A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18233
SUBJECT: Konus-Wind observation of GRB 150902A
DATE:    15/09/03 16:00:52 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

S. Golenetskii, R. Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, A. Kozlova,
and T. Cline on behalf of the Konus-Wind team, report:

The long-duration, very bright GRB 150902A
(Fermi LAT detection: Arimoto et al., GCN Circ. 18228;
Fermi GBM detection: Roberts and Younes, GCN Circ. 18229)
triggered Konus-Wind at T0=63340.850 s UT (17:35:40.850).

The burst light curve shows a single pulse with
a total duration of ~20 s followed by a weak tail up to ~100 s.
The emission is seen up to ~18 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB150902_T63340/

As observed by Konus-Wind, the burst
had a fluence of 1.21(-0.07,+0.07)x10^-4 erg/cm2,
and a 64-ms peak flux, measured from T0+6.384 s,
of 2.13(-0.27,+0.28)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+25.600 s)
is best fit in the 20 keV - 18 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.58(-0.06,+0.07),
the high energy photon index beta = -2.30(-0.11,+0.09),
the peak energy 322(-21,+23) keV
(chi2 = 138/96 dof)

The spectrum near the maximum count rate
(measured from T0+6.144 to T0+6.656 s)
is best fit in the 20 keV - 11 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.02(-0.18,+0.21),
the high energy photon index beta = -2.75(-0.39,+0.23),
the peak energy 288(-33,+37) keV
(chi2 = 77/47 dof)

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.


GRB_name: GRB150902A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18234
SUBJECT: GRB 150902A: MASTER-SAAO optical observations
DATE:    15/09/03 16:56:26 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

D.Buckley, S. Potter, A.Kniazev, M.Kotze
South African Astronomical Observatory

E. Gorbovskoy,  V. Lipunov,  N.Tyurina, V.Kornilov, P.Balanutsa, A.Kuznetsov, 
E.Popova, D.Kuvshinov,
Lomonosov Moscow State University, Sternberg Astronomical Institute

R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres
The Instituto de Astrofisica de Canarias

A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik
Kislovodsk Solar Station of the Pulkovo Observatory

K.Ivanov, O.Gres, N.M.Budnev, S.Yazev, O.Chuvalaev, V.A.Poleshchuk
Irkutsk State University

V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov, A.Gabovich
Blagoveschensk Educational State University, Blagoveschensk

V.Krushinski, I.Zalozhnih
Ural Federal University, Kourovka

Hugo Levato and Carlos Saffe
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)

Carlos Lopez, Claudio Mallamaci and Federico Podest
Observatorio Astronomico Felix Aguilar (OAFA)



MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in SAAO was firstly pointed to the  GRB150902A (Roberts et. al. 
GCN 18229) 67 sec after trigger time at 2015-09-02 17:36:47 UT. On our 
first (10s exposure)  set we not  found  optical transient within FERMI 
error-box (ra=16 24 36 dec=-72 54 35 r=2.140000) brighter then 15.27. 
MASTER-SAAO robotic telescope  makes several alert and inspect 
observations inside actual (at that time) FERMI GBM error boxes, but all 
of that frames   located  far away from the final FERMI LAT  (Arimoto et. 
al GCN 18228) error box and did not cover it.

MASTER-VWF very wide fileld cameras placed in MASTER-SAAO cover FERMI LAT 
error box at 2015-09-02 17:36:32.0 i.e. 47 sec after notice and 53 sec 
after trigger time, and imaging it continuously without time gaps till 
2015-09-02 17:43:00. We have not find OT inside FERMI LAT error box with 
upper limit 11.5m on single (5 second) and 12.8m ( on coadd of 12 frames 
with total exposure 60 s) images.

  The message may be cited.


GRB_name: GRB150831A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18235
SUBJECT: GRB 150831A: 9.8 GHz VLA upper limits
DATE:    15/09/04 00:16:23 GMT
FROM:    Wen-fai Fong at U of Arizona  <wfong@email.arizona.edu>

W. Fong (U. Arizona) and B. A. Zauderer (Harvard) report:

"We observed the field of the short-duration GRB 150831A (Lien et al., GCN
18209) with the Karl G. Jansky Very Large Array (VLA) beginning on 2015 Aug
31.934 UT (11.9 hr post-burst) at a mean frequency of 9.8 GHz. In 1 hour of
observations, we do not detect any radio source within or around the
enhanced XRT position (Osborne et al., GCN 18212) to a 3-sigma limit of 25
microJy. Furthermore, we obtained a second set of observations beginning on
2015 Sep 2.954 UT (2.5 days post-burst) at a mean frequency of 9.8 GHz and
do not detect any radio source in or around the XRT position to a 3-sigma
limit of 21 microJy.

We therefore place 3-sigma limits of 25 microJy and 21 microJy on the radio
afterglow of GRB 150831A at 11.9 hr and 2.5 days after the burst,
respectively.

We thank the VLA staff for quickly executing these observations."


GRB_name: GRB150902A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18237
SUBJECT: GRB 150902A: Swift-XRT observations
DATE:    15/09/04 14:55:37 GMT
FROM:    Boris Sbarufatti at INAF-OAB/IASFPA  <boris.sbarufatti@brera.inaf.it>

L.M. McCauley (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU),
A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), V. D'Elia
(ASDC), A. D'ai (INAF-IASFPA), A. Maselli  (INAF-IASFPA) and P.A. Evans
(U. Leicester) report on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the
Fermi/LAT-detected burst GRB 150902A (Arimoto et al. GCN Circ. 18228),
collecting 4.9 ks of Photon Counting (PC) mode data between T0+59.6 ks
and T0+78.6 ks. 

Two uncatalogued X-ray sources have been detected inside or close to
the Fermi/LAT error region, however none of them is above the RASS
limit or shows definitive signs of fading. Therefore, at the present
time we cannot identify which, if any, is the afterglow. Details of
these sources are given below:

Source 1:
  RA (J2000):  214.9797  =  14:19:55.13
  Dec (J2000): -69.3535  =  -69:21:12.6
  Error: 4.4 arcsec (radius, 90% conf.)
  Count-rate: 0.0116 +/- 0.0022 ct s^-1
  Flux: (5.16 +/- 0.98)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 2:
  RA (J2000):  215.2707  =  14:21:4.97
  Dec (J2000): -69.4918  =  -69:29:30.3
  Error: 8.2 arcsec (radius, 90% conf.)
  Count-rate: (5.1 +/- 1.5)e-3 ct s^-1
  Flux: (2.07 +/- 0.62)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
http://www.swift.ac.uk/ToO_GRBs/00020549.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB150902A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18238
SUBJECT: GRB 150902A: Swift/UVOT Upper Limits
DATE:    15/09/04 15:37:25 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld@ucl.ac.uk>

A. A. Breeveld (UCL-MSSL) and L. Hagen (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150902A
59510 s after the LAT trigger (Arimoto et al., GCN Circ. 18228).
No optical afterglow consistent with the XRT Source 1 position given in 
McCauley et al. (GCN Circ. 18237) is detected in the initial UVOT 
exposures. Source 2 is outside the UVOT field of view.

Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial 
exposures for source 1 are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag
white            60331        60972          631         >21.7
v                61152        61997          828         >20.3
u                59510        66787         1184         >20.7

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.40 in the direction of the 
burst (Schlegel et al. 1998).


GRB_name: GRB150902A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18243
SUBJECT: GRB 150902A: Swift-XRT afterglow detection
DATE:    15/09/05 14:09:50 GMT
FROM:    Boris Sbarufatti at INAF-OAB/IASFPA  <boris.sbarufatti@brera.inaf.it>

L.M. McCauley (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU),
A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), V. D'Elia
(ASDC), A. D'ai (INAF-IASFPA), A. Maselli  (INAF-IASFPA) and P.A. Evans
(U. Leicester) report on behalf of the Swift-XRT team:

Swift-XRT has conducted further observations of the field of the
Fermi/LAT-detected burst GRB 150902A (Arimoto et al. GCN Circ. 18228).
The observations now extend from T0+59.5 ks to T0+192.1 ks. 

Of the sources reported by McCauley et al. (GCN Circ. 18237), "Source
1" is  believed to be the afterglow.  The position of this source is
RA, Dec=214.9796, -69.3536 which is equivalent to:

RA (J2000): 14:19:55.09
Dec(J2000): -69:21:13.1

with an uncertainty of 4.3 arcsec (radius, 90% confidence).  This
position is 73 arcsec from the Fermi/LAT position. 

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.0 (+0.7, -0.4).

The results of the XRT-team automatic analysis of the likely afterglow
are at http://www.swift.ac.uk/ToO_GRBs/00020549/index_1.php.
The results of the full analysis of the XRT observations are available
at http://www.swift.ac.uk/ToO_GRBs/00020549.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB150818A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18244
SUBJECT: GRB 150818A: TSHAO and SAO RAS optical observations
DATE:    15/09/07 09:29:09 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

E. Mazaeva (IKI), A. Moskvitin (SAO RAS), I. Reva (Fesenkov 
Astrophysical Institute),  A. Kusakin (Fesenkov Astrophysical 
Institute),  A. Volnova (IKI), A. Pozanenko  (IKI) report on behalf of 
larger GRB follow-up collaboration:

We are continuing observations the field of Swift GRB 150818A (D'Elia et 
al., GCNC 18152) with Zeiss-1000  1-m telescope of Tien Shan 
Astronomical Observatory and Zeiss-1000, 1-m telescope of SAO RAS. The 
optical transient (Marshall et al. GCN 18155; McCauley et al. GCN 18161; 
Mazaeva et al. GCN 18175; Sanchez-Ramirez et al. GCN 18177; Mazaeva et 
al. GCN 18182, GCN 18189, GCN 18205; Schulze et al. GCN 18179) is 
clearly visible on combined images in each epochs. The updated light 
curve of Supernova (de Ugarte Postigo et al. GCN 18213; Mazaeva et al. 
GCN 18205) + host galaxy (Sanchez-Ramirez et al., GCN 18177; de Ugarte 
Postigo et al. GCN 18213) can be found in

http://grb.rssi.ru/GRB150818A/GRB150818A_R_lc.png

The evident maximum of SN brightness (in Rc-filter) was on ~ Sep. 1-2, 
and the brightness of SN+host galaxy was R ~ 21.1 +/- 0.1 on Sep. 6 (UT) 
18:00. We are grateful to V.P. Goranskiy for assistance in SAO RAS 
observations.


GRB_name: GRB150906A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18245
SUBJECT: GRB 150906A: Fermi GBM detection
DATE:    15/09/07 16:30:19 GMT
FROM:    Oliver Roberts at UCD/Fermi  <oliver.roberts@ucd.ie>

O.J. Roberts (UCD), G. Younes (GWU), and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 22:38:47.31 UT on the 6th of September 2015, the Fermi
Gamma-Ray Burst Monitor triggered and located GRB 150906A
(trigger 463271931 / 150906944).

The on-ground calculated location, using the GBM trigger
data, is RA = 212.04, DEC = 1.09 (J2000 degrees,
equivalent to 14h 08m 9.6s, +01d 5' 24" ), with an uncertainty of
5.19 degrees (radius, 1-sigma containment, statistical
only; there is additionally a systematic error which we
have characterized as a core-plus-tail model, with 90%
of GRBs having a 3.7 deg error and a small tail suffering
a larger than 10 deg systematic error.
[Connaughton et al. 2015, ApJS, 216, 32]).

The angle from the Fermi LAT boresight at the GBM trigger
time is 29 degrees.

The trigger resulted in an Autonomous Repoint Request
(ARR) by the GBM Flight Software owing to the high peak
flux and hardness of the GRB. This ARR was accepted and
the spacecraft slewed to the GBM in-flight location.

The GBM light curve consists of a single short pulse, with
a duration (T90) of about 1 s (50-300 keV). The
time-averaged spectrum from T0-0.064 s to T0+0.064 s is
adequately fit by a power law function with an exponential
high-energy cutoff. The power law index is -0.60 +/- 0.16
and the cutoff energy, parameterized as Epeak,
is 597 +/- 130 keV

The event fluence (10-1000 keV) in this time interval is
4.944 +/- 0.384)E-07 erg/cm^2. The 64 ms peak photon flux
measured starting from T0-0.064 s in the 8-1000 keV band
is 13.6 +/- 1.4 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."


GRB_name: GRB150907A
Detection_method: MAXI Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18246
SUBJECT: GRB 150907A: MAXI/GSC detection
DATE:    15/09/07 17:46:13 GMT
FROM:    Motoko Suzuki at RIKEN  <motoko@crab.riken.jp>

Y. E. Nakagawa (JAXA), H. Negoro, (Nihon U.), M. Serino (RIKEN),
M. Ishikawa, S. Nakahira, S. Ueno, H. Tomida,  M. Kimura(JAXA),
T. Mihara, M. Sugizaki,  M. Shidatsu, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN), 
N. Kawai, Y. Tachibana, T. Yoshii (Tokyo Tech),
A. Yoshida, T. Sakamoto, Y. Kawakubo, H. Ohtsuki (AGU), 
H. Tsunemi, R. Imatani (Osaka U.), M. Nakajima, T. Masumitsu, K. Tanaka (Nihon U.), 
Y. Ueda, T. Kawamuro, T. Hori (Kyoto U.), Y. Tsuboi, S. Kanetou (Chuo U.), 
M. Yamauchi, D. Itoh (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Morii (ISM) 
report on behalf of the MAXI team:

The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at
16:00:50 UT on 7 September 2015. Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (224.845 deg, -47.592 deg) = (14 59 22, -47 35 31) (J2000)
with a 90% C.L. statistical error of 0.06 deg. 
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 1464 +- 75 mCrab (4-10keV, 1 sigma error).
There was no significant excess flux in the previous transit at 14:28 UT on 7 September 2015
with an upper limit of 20 mCrab.


GRB_name: GRB150907A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18247
SUBJECT: GRB 150907A: Tiled Swift observations
DATE:    15/09/07 18:37:17 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a series of observations, tiled on the sky, of the
MAXI GRB 150907A. Automated analysis of the XRT data will
be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00048

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. The probability of finding
serendipitous sources, unrelated to the MAXI event is high: any X-ray source
considered to be a probable afterglow candidate will be reported via a GCN Circular
after manual consideration.

Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).

This circular is an official product of the Swift-XRT team.


GRB_name: GRB150907B
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18249
SUBJECT: GRB 150907B: Swift detection of a burst
DATE:    15/09/07 23:37:45 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

T. G. R. Roegiers (PSU), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC),
D. M. Palmer (LANL), B. Sbarufatti (INAF-OAB/PSU) and
T. N. Ukwatta (LANL) report on behalf of the Swift Team:

At 23:26:27 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150907B (trigger=654803).  Swift could not slew
immediately to the burst due to an observing constraint. 
The BAT on-board calculated location is 
RA, Dec 255.219, -63.819 which is 
   RA(J2000) = 17h 00m 53s
   Dec(J2000) = -63d 49' 07"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  Only partial BAT lightcurve data is available,
but the light curve shows a complex structure at least 10 seconds long. 
The peak count rate was ~1500 counts/sec (15-350 keV), at ~0 sec 
after the trigger. 

Due to an observing constraint, Swift will not slew until T0+49.0
minutes. There will be no XRT or UVOT data until this time. 

Burst Advocate for this burst is T. G. R. Roegiers (troegiers AT swift.psu.edu). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)


GRB_name: GRB150907A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18250
SUBJECT: GRB 150907A: Swift-XRT observations
DATE:    15/09/08 00:52:27 GMT
FROM:    Tineke Roegiers at PSU  <troegiers@swift.psu.edu>

J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), T.G.R. Roegiers (PSU),
J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A. D'ai
(INAF-IASFPA), A. Maselli  (INAF-IASFPA), A. Melandri (INAF-OAB), D.N.
Burrows (PSU) and P.A. Evans (U. Leicester) report on behalf of the
Swift-XRT team:

Swift-XRT has performed follow-up observations of the MAXI-detected
burst GRB 150907A (Nakagawa et al. GCN Circ. 18246) in a series of
observations tiled on the sky. The total exposure time is 1.7 ks,
distributed over 4 tiles; the maximum exposure at a single sky location
was 1.1 ks. The data were collected between T0+8.8 ks and T0+18.8 ks,
and are entirely in Photon Counting (PC) mode. 

One uncatalogued X-ray source has been detected, it is below the RASS
limit and shows no definitive signs of fading. Therefore, at the
present time we cannot confirm this as the afterglow. Details of this
source are given below:

Source 1:
  RA (J2000):  225.0526  =  15:00:12.62
  Dec (J2000): -47.7084  =  -47:42:30.3
  Error: 6.0 arcsec (radius, 90% conf.)
  Count-rate: 0.037 +/- 0.010 ct s^-1
  Flux: (2.50 +/- 0.70)e-12 erg cm^-2 s^-1 (observed, 0.3-10 keV)

The results of the XRT-team automatic analysis of the tiled XRT
observations, including a position-specific upper limit calculator, are
available at http://www.swift.ac.uk/xrt_products/TILED_GRB00048.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB150907B
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18251
SUBJECT: GRB 150907B: Swift-XRT observations
DATE:    15/09/08 00:54:41 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

J.P. Osborne (U. Leicester), D.N. Burrows (PSU), J.A. Kennea (PSU), G.
Cusumano (INAF-IASF PA), M. Perri (ASDC) and P.A. Evans (U. Leicester)
report on behalf of the Swift-XRT team:

The XRT began observing the field of GRB 150907B at 00:16:37.8 UT,
3010.0 seconds after the BAT trigger. Using promptly downlinked data we
find an uncatalogued X-ray source located at RA, Dec 255.30809,
-63.78591 which is equivalent to:
   RA(J2000)  = 17h 01m 13.94s
   Dec(J2000) = -63d 47' 09.3"
with an uncertainty of 4.0 arcseconds (radius, 90% containment). This
location is 185 arcseconds from the BAT onboard position, outside the
BAT error circle. This position may be improved as more data are
received; the latest position is available at
http://www.swift.ac.uk/sper.  We cannot determine whether the source is
fading at the present time. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 1.52
x 10^21 cm^-2 (Willingale et al. 2013). 


GRB_name: GRB150907B
Detection_method: GROND
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18252
SUBJECT: GRB 150907B: GROND Upper Limits
DATE:    15/09/08 05:47:06 GMT
FROM:    Philip Wiseman at MPE/Swift  <wiseman@mpe.mpg.de>

P. Wiseman, C. Delvaux and J. Greiner (all MPE Garching) report on behalf
of the GROND team:

We observed the field of GRB 150907B (Swift trigger 654803; Roegiers et
al., GCN #18249) simultaneously in g'r'i'z'JHK with GROND (Greiner et al.
2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla
Observatory (Chile).

Observations started at 02:03 UT on 08/09/2015, 2.63 hours after the GRB
trigger. They were performed at an average seeing of 2.5" and an average
airmass of 2.0.

We do not detect a source within the Swift-XRT error circle reported by
Osborne et al. (GCN #18251) down to limits of:

g' > 24.5 mag,

r' > 23.9 mag,

i' > 23.3 mag,

z' > 23.2 mag,

J > 21.1 mag,

H > 20.6 mag, and

K > 19.2 mag.

We note a source at the eastern edge of the Swift-XRT error circle, at a
position:
RA  =  255.3110
Dec = -63.7860,
or 17h 01m 14.64s -64d 47' 09.6".

This source does not seem to be fading, and with a non GRB-like SED, and
matches to the known source S7FP064671 from The Guide Star Catalogue,
Version 2.3.2 (Lasker B., Lattanzi M.G., McLean B.J., et al. Astron. J.
136, 735 (2008)).

The given limits are derived based on calibrating the images against GROND
zeropoints and 2MASS field stars and are not corrected for the Galactic
foreground extinction corresponding to a reddening of E_(B-V)= 0.1432 in
the direction of the burst (Schlegel et al. 1998).


GRB_name: GRB150907B
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18253
SUBJECT: GRB 150907B: Enhanced Swift-XRT position
DATE:    15/09/08 06:27:12 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 3059 s of XRT Photon Counting mode data and 4 UVOT
images for GRB 150907B, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 255.30407, -63.78510 which is equivalent
to:

RA (J2000): 17h 01m 12.98s
Dec (J2000): -63d 47' 06.4"

with an uncertainty of 1.9 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.


GRB_name: GRB150907B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18254
SUBJECT: GRB 150907B: MASTER-SAAO early optical observations 
DATE:    15/09/08 08:22:48 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

D.Buckley, S. Potter, M.Kotze
South African Astronomical Observatory

V. Lipunov, E.Gorbovskoy,  N.Tyurina, V.Kornilov, P.Balanutsa, 
A.Kuznetsov, D.Kuvshinov, I.Gorbunov
Lomonosov Moscow State University, Sternberg Astronomical Institute

R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres
The Instituto de Astrofisica de Canarias

A. Tlatov, D. Dormidontov, V.Senik
Kislovodsk Solar Station of the Pulkovo Observatory

K.Ivanov, O.Gres, N.M.Budnev, S.Yazev, O.Chuvalaev, V.A.Poleshchuk
Irkutsk State University

V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov, A.Gabovich
Blagoveschensk Educational State University, Blagoveschensk

V.Krushinski, I.Zalozhnih
Ural Federal University, Kourovka

Hugo Levato and Carlos Saffe
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)

Carlos Lopez, Claudio Mallamaci and Federico Podest
Observatorio Astronomico Felix Aguilar (OAFA)



MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in SAAO was pointed to the Swift Alert (Roegiers et al., GCN 
18249) GRB150907B 25 sec after notice time 
and 40 sec after trigger time at 2015-09-07 23:27:10 UT. On our first (10s 
exposure)  set we haven't found optical transient  within SWIFT error-box 
(ra=17 00 51 dec=-63 49 07 r=0.050000).
The next images limit without OT:

  Id      Coord             Pro.type Time,UT Exp.time  Lim Filt. Tube

110113 16h 59m 04.1s -63d 41m 01s  Alert  23:27:10  10     15.5  P  EAST
110114 17h 00m 00.1s -63d 42m 55s  Alert  23:27:10  10     15.7  P  WEST
110115 16h 59m 47.7s -63d 42m 57s  Alert  23:27:34  10     15.4  P  WEST
110116 16h 59m 22.0s -63d 41m 10s  Alert  23:27:34  10     15.2  P  EAST
110117 16h 59m 47.5s -63d 42m 57s  Alert  23:27:56  20     15.9  P  WEST
110118 16h 59m 21.8s -63d 41m 10s  Alert  23:27:56  20     15.7  P  EAST
110119 16h 59m 21.6s -63d 41m 09s  Alert  23:28:27  20     15.9  P  EAST
110120 16h 59m 47.4s -63d 42m 56s  Alert  23:28:27  20     16.1  P  WEST
110121 16h 59m 21.6s -63d 41m 09s  Alert  23:28:58  30     13.2  P  EAST
110122 16h 59m 47.4s -63d 42m 56s  Alert  23:28:58  30     13.5  P  WEST
110123 17h 00m 00.1s -63d 42m 55s SumAlert23:27:10  40     16.3  P  WEST
110124 16h 59m 21.4s -63d 41m 08s  Alert  23:29:39  40     15.1  P  EAST
110125 16h 59m 47.1s -63d 42m 55s  Alert  23:29:39  40     15.5  P  WEST
110126 16h 59m 04.1s -63d 41m 01s SumAlert23:27:10  40     16.1  P  EAST
110127 16h 59m 47.1s -63d 42m 55s  Alert  23:30:30  50     15.9  P  WEST
110128 16h 59m 21.3s -63d 41m 08s  Alert  23:30:30  50     15.5  P  EAST
110129 16h 59m 47.4s -63d 42m 56s SumAlert23:28:27  90     15.9  P  WEST
110130 16h 59m 21.2s -63d 41m 08s  Alert  23:31:31  60     14.8  P  EAST
110131 16h 59m 47.1s -63d 42m 56s  Alert  23:31:31  60     15.4  P  WEST
110132 16h 59m 21.6s -63d 41m 09s SumAlert23:28:27  110    16.1  P  EAST

There was a short time between rain and clouds. Then the clouds returned.

The message may be cited.


GRB_name: GRB150907A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18255
SUBJECT: GRB150907A: Swift/UVOT observations
DATE:    15/09/08 11:57:36 GMT
FROM:    Massimiliano de Pasquale at IASF-Palermo  <m.depasquale@ucl.ac.uk>

M. De Pasquale (UCL-MSSL) and D. Malesani (DARK/NBI) report on behalf of
the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150907A
8821 s after the MAXI trigger (Suzuki et al., GCN Circ. 18246).

No optical source consistent with the XRT Source 1 position given in
Kennea et al. (GCN Circ. 18250) is detected in the summed u band exposures.

We note however, that there is source in the DSS catalogue consistent
with the XRT Source 1 position.


Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the exposure
for source 1 is:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

u                8821        18835         336           >19.5


The magnitudes in the table are not corrected for the Galactic 
extinction due
to the reddening of E(B-V) = 0.08 in the direction of the burst 
(Schlegel et al. 1998).

-- 

Dr. Massimiliano De Pasquale
Research associate - Swift UVOT scientist
Mullard Space Science Laboratory, University College London


GRB_name: GRB150907B
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18256
SUBJECT: GRB 150907B: Swift-BAT refined analysis
DATE:    15/09/08 12:27:43 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>

H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. G. R. Roegiers (PSU), T. Sakamoto (AGU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
 
Using the data set from T-240 to T+962 sec from the recent telemetry downlinks,
we report further analysis of BAT GRB 150907B (trigger #654803)
(Roegiers, et al., GCN Circ. 18249).  The BAT ground-calculated position is
RA, Dec = 255.265, -63.798 deg, which is 
   RA(J2000)  =  17h 01m 03.5s 
   Dec(J2000) = -63d 47' 51.6" 
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 50%.
 
The mask-weighted light curve shows a Fred-like starting at ~T-1 sec,
peaking at ~T+1 sec, and ending around T+100 sec.
T90 (15-350 keV) is 62.0 +- 11.1 sec (estimated error including systematics).
 
The time-averaged spectrum from T-1.48 to T+64.53 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 0.17 +- 1.03, 
and Epeak of 67.4 +- 29.7 keV (chi squared 53.2 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 1.1 +- 0.2 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+0.59 sec in the 15-150 keV band is
1.0 +- 0.2 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.47 +- 0.18 (chi squared 59.8 for 57 d.o.f.).  All the quoted errors
are at the 90% confidence level. 
 
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/654803/BA/


GRB_name: GRB150906B
Detection_method: IPN Triangulation
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18258
SUBJECT: IPN Triangulation of GRB 150906B (short/intense)
DATE:    15/09/08 17:10:06 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

K. Hurley, on behalf of the IPN,

I. G. Mitrofanov, D. Golovin, M. L. Litvak, and A. B. Sanin,
on behalf of the HEND-Odyssey GRB team,

S. Golenetskii, R. Aptekar, V. Pal'shin, D. Frederiks,
D. Svinkin, and T. Cline on behalf of the Konus-Wind team,

S. Barthelmy, J. Cummings, N. Gehrels, H. Krimm, and D. Palmer,
on behalf of the Swift-BAT team,

A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
and

W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr,
on behalf of the GRS-Odyssey GRB team, report:

The short-duration, intense GRB 150906B has been detected by Konus-Wind, 
INTEGRAL (SPI-ACS), Mars-Odyssey (HEND), and Swift (BAT), so far, at 
about 31345 s UT (08:42:25). The burst was outside the coded field of 
view of the BAT.

We have triangulated it to a preliminary, 3 sigma error box whose 
coordinates are:
---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   159.239 (10h 36m 57s) -25.603 (-25d 36' 09")
  Corners:
   158.968 (10h 35m 52s) -25.638 (-25d 38' 17")
   159.102 (10h 36m 24s) -25.740 (-25d 44' 23")
   159.510 (10h 38m 02s) -25.566 (-25d 33' 57")
   159.376 (10h 37m 30s) -25.465 (-25d 27' 54")
  ---------------------------------------------
The error box area is 210 sq. arcmin, and its maximum
dimension is 30 arcmin (the minimum one is 8.6 arcmin).
The Sun distance was 32 deg.

This box may be improved.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB150906_T31340/IPN/

The Konus-Wind time history and spectrum will be given in a forthcoming 
GCN Circular.


GRB_name: GRB150906B
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18259
SUBJECT: Konus-Wind observation of GRB 150906B
DATE:    15/09/08 18:12:45 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred@mail.ioffe.ru>

S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik, M. 
Ulanov, D. Svinkin, A. Tsvetkova, A.Lysenko, A.Kozlova, and T. Cline
on behalf of the Konus-Wind team, report:

The short-duration, hard-spectrum  GRB 150906B
(IPN triangulation:  Hurley, et al., GCN 18258)
triggered Konus-Wind at 31340.560 s UT (08:42:20.560).

The KW light curve shows a single, multi-peaked pulse
with a duration of ~2 s.
The emission is visible up to ~10 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB150906_T31340/

As observed by Konus-Wind, the burst had a fluence
of 2.8(-0.2,+0.2)x10^-5 erg/cm2, and a 16-ms peak flux,
measured from T0+1.488 s, of 2.9(-0.3,+0.3)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum (measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 15 MeV range
by the cutoff power law with the following model parameters:
the photon index alpha = -0.43(-0.11,+0.12),
and the peak energy Ep = 928(-95,+111) keV,
chi2 = 93/94 dof.
Fitting this spectrum with the GRB (Band) function yields
the same alpha and Ep with an upper limit on beta of -2.8

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.


GRB_name: GRB150907B
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18260
SUBJECT: GRB 150907B: Swift-XRT refined Analysis
DATE:    15/09/08 18:29:56 GMT
FROM:    Tineke Roegiers at PSU  <troegiers@swift.psu.edu>

B. Sbarufatti (INAF-OAB/PSU), J.P. Osborne (U. Leicester), K.L. Page
(U. Leicester), C. Pagani (U. Leicester), A. Maselli  (INAF-IASFPA), A.
Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), D.N. Burrows (PSU) and T.
G. R. Roegiers (PSU) report on behalf of the Swift-XRT team:

We have analysed 7.9 ks of XRT data for GRB 150907B (Roegiers et al.
GCN Circ. 18249), from 3.0 ks to 32.2 ks after the  BAT trigger. The
data are entirely in Photon Counting (PC) mode. The enhanced XRT
position for this burst was given by Beardmore et al. (GCN Circ.
18253).

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.61 (+0.37, -0.28).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.02 (+0.28, -0.35). The
best-fitting absorption column is  4.4 (+7.7, -1.8) x 10^21 cm^-2, in
excess of the Galactic value of 1.5 x 10^21 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 4.1 x 10^-11 (6.7 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      4.4 (+7.7, -1.8) x 10^21 cm^-2
Galactic foreground: 1.5 x 10^21 cm^-2
Excess significance: 2.6 sigma
Photon index:      2.02 (+0.28, -0.35)

If the light curve continues to decay with a power-law decay index of
1.61, the count rate at T+24 hours will be 3.4 x 10^-4 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.4 x
10^-14 (2.3 x 10^-14) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00654803.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB150906B
Detection_method: IPN Triangulation
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18263
SUBJECT: Short GRB 150906B: proximity to NGC 3313 galaxy group
DATE:    15/09/09 08:45:20 GMT
FROM:    Nial Tanvir at U.Leicester  <nrt3@star.le.ac.uk>

A. J. Levan (U. Warwick), N. R. Tanvir (U. Leicester) and J. Hjorth (DARK/NBI) report:

We note that the preliminary IPN localisation of the short, intense GRB 150906B (Hurley et al. GCN 18258, Golenetskii et al. GCN 18259) lies close to the local galaxy NGC 3313 (z=0.0124, d=54 Mpc). At its closest the IPN error box passes approximately 8.5 arc minutes from the centre of the galaxy, which has a major diameter of 4 arc minutes. This offset corresponds to approximately 130 kpc in projection at 54 Mpc, and is within the range that either kicked neutron star binaries or globular clusters associated with NGC 3313 may be found. In fact, NGC 3313 is the brightest galaxy of a moderate group, and there are several other fainter group members (presumably with shallower potential wells and hence greater typical binary neutron star kick offsets) that lie comparably close to the IPN error region, which are thus also candidate hosts. An image showing the IPN region and group members is at http://www.star.le.ac.uk/~nrt3/NGC3313_group.png .

At 54 Mpc the inferred isotropic energy of GRB 150906B would be E_iso ~ 10^49 erg, within the range of energetics of known short-GRBs.

Although it is certainly plausible that the proximity of GRB 150906B to NGC 3313 is a chance alignment, it is of particular interest given that NGC 3313 lies well within the expected detection horizon of Advanced-LIGO/VIRGO for compact binary mergers. Unfortunately the sky location of GRB 150906B means that it is very poorly placed for optical/IR observations at this time.


GRB_name: GRB150910A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18264
SUBJECT: GRB 150910A: Swift detection of a burst with an optical afterglow
DATE:    15/09/10 09:26:53 GMT
FROM:    Kim Page at U.of Leicester  <klp5@leicester.ac.uk>

C. Pagani (U Leicester), A. P. Beardmore (U Leicester),
A. A. Breeveld (UCL-MSSL), K. L. Page (U Leicester),
P. Romano (INAF-IASFPA) and T. N. Ukwatta (LANL) report on behalf of
the Swift Team:

At 09:04:48 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150910A (trigger=655097). Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 5.675, +33.499 which is 
   RA(J2000) = 00h 22m 42s
   Dec(J2000) = +33d 29' 55"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty). As is typical for image triggers, the real-time
light curve does not show anything significant. 

The XRT began observing the field at 09:07:14.1 UT, 145.3 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 5.6669, 33.4717 which is equivalent to:
   RA(J2000)  = +00h 22m 40.06s
   Dec(J2000) = +33d 28' 18.1"
with an uncertainty of 5.1 arcseconds (radius, 90% containment). This
location is 101 arcseconds from the BAT onboard position, within the
BAT error circle. No event data are yet available to determine the
column density using X-ray spectroscopy. 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 153 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  = 00:22:40.14 = 5.66723
  DEC(J2000) = +33:28:21.9  =  33.47275
with a 90%-confidence error radius of about 0.71 arc sec. This position is 3.9
arc sec. from the center of the XRT error circle. The estimated magnitude is
20.27 with a 1-sigma error of about  0.18. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.05. 

Burst Advocate for this burst is C. Pagani (cp232 AT star.le.ac.uk). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)


GRB_name: GRB150910A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18265
SUBJECT: GRB 150910A: KAIT Optical Afterglow Detection
DATE:    15/09/10 10:00:52 GMT
FROM:    Weikang Zheng at UC Berkeley  <weikang@berkeley.edu>

WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on
behalf of the KAIT GRB team:

The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, responded to Swift GRB 150910A (Pagani
et al., GCN 18264) starting at 09:34:20 UT, ~30 minutes after
the burst. Observations were performed with an automatic sequence
in the clear (roughly R), V, and I filters, and the exposure time was
20 s per image. The UVOT afterglow reported by Pagani et al. (GCN 18264)
was clearly detected in all filters. The brightness is about R~16.2 mag
at ~30 minutes after the burst, and is decreasing.
Follow-up observations are encouraged.


GRB_name: GRB150910A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18266
SUBJECT: GRB 150910A: LCOGT FTN afterglow observations
DATE:    15/09/10 11:05:14 GMT
FROM:    Cristiano Guidorzi at Ferrara U,Italy  <guidorzi@fe.infn.it>

S. Dichiara, C. Guidorzi (U. Ferrara), S. Kobayashi (LJMU), A. Gomboc 
(U. Ljubljana), C. Mundell (U. Bath) on behalf of a larger collaboration 
report:

The 2-m LCOGT Faulkes Telescope North in Hawaii began observing Swift 
GRB 150910A (Pagani et al. GCN 18264) on September 10, 09:33:19 UT (28 
minutes after the burst trigger) with SDSS r and i filters. We clearly 
detect the optical afterglow (Pagani et al. GCN 18264; Zheng et al. GCN 
18265) with the following magnitudes:

Mid Time      Exposure       Filter       Magnitude
(min)           (s)
-------------------------------------------------------
29.0             60          r'           16.60 +- 0.02
35.6             60          i'           16.42 +- 0.02
-------------------------------------------------------

Calibration is done against SDSS magnitudes of nearby stars.


GRB_name: GRB150910A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18267
SUBJECT: GRB 150910A: MITSuME Okayama Optical Observation
DATE:    15/09/10 11:41:03 GMT
FROM:    Daisuke Kuroda at OAO/NAOJ  <dikuroda@oao.nao.ac.jp>

D. Kuroda, K. Yanagisawa, Y. Shimizu, H. Toda (OAO, NAOJ),
S. Nagayama (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto)
and N. Kawai(Tokyo Tech)
report on behalf of the MITSuME and OISTER collaboration:

We observed the field of GRB 150910A (Pagani et al., GCNC 18264)
with the optical three color (g', Rc and Ic) CCD camera attached
to the MITSuME 50cm telescope of Okayama Astrophysical Observatory.

The observation started on 2015-09-10 10:20:44 UT (~1.3 h after
the burst). We detected the previously reported afterglow (Pagani
et al., GCNC 18264; Zheng and Filippenko, GCNC 18265; Dichiara
et al., GCNC 18266) in all the three bands.

Photometric results of the OT are listed below.
We used SDSS-DR7 catalog for flux calibration.

#T0+[day]  MID-UT    T-EXP[sec]   g'  g'_err  Rc  Rc_err  Ic  Ic_err
-----------------------------------------------------------------------
0.05630    10:25:52     540.0     17.6 0.2    18.4 0.2    17.0 0.1
------------------------------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]


GRB_name: GRB150910A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18268
SUBJECT: GRB 150910A: Swift-BAT refined analysis
DATE:    15/09/10 13:19:46 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>

A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC),
C. Pagani (U Leicester), D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
 
Using the data set from T-239 to T+963 sec from the recent telemetry downlinks,
we report further analysis of BAT GRB 150910A (trigger #655097)
(Pagani, et al., GCN Circ. 18264).  The BAT ground-calculated position is
RA, Dec = 5.677, 33.466 deg, which is 
   RA(J2000)  =  00h 22m 42.5s 
   Dec(J2000) = +33d 27' 56.8" 
with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 14%.
 
The mask-weighted light curve shows the burst definitely starting at ~T-150 sec
(and posibly before T-240 when we start having data), peaking at ~T+83 sec,
and ending at ~T+450 sec.  T90 (15-350 keV) is 112.2 +- 38.3 sec
(estimated error including systematics).
 
The time-averaged spectrum from T-5.00 to T+149.75 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.42 +- 0.12.  The fluence in the 15-150 keV band is 4.8 +- 0.4 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+82.89 sec in the 15-150 keV band
is 1.1 +- 0.4 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level. 
 
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/655097/BA/


GRB_name: GRB150910A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18269
SUBJECT: GRB 150910A: Nanshan optical observations
DATE:    15/09/10 14:50:26 GMT
FROM:    Dong Xu at NAOC/CAS  <dong.dark@gmail.com>

D. Xu (NAOC/CAS), Y. Qin (Geneva Observatory), Y.-D. Hu (IAA-CSIC),
Y.-H. Han (NAOC/CAS, HUST), X. Zhang, A. Esamdin, L. Ma (XAO) report:

We observed the field of GRB 150910A (Pagani et al., GCN 18264) using
the 1m telescope located at Nanshan, Xinjiang, China. We obtained
3x600s R-band frames with some floating clouds in the sky.

The afterglow (Pagani et al., GCN 18264; Zheng & Filippenko, GCN
18265) is detected in each of the frames. Preliminary results are as
follows

Mid Time  Exposure  Mag   MagErr
(hr)            (s)
4.91         600          19.40    0.20
5.14         600          19.55    0.20
5.31         600          19.30    0.20

and calibrated with the nearby SDSS field.


GRB_name: GRB150910A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18270
SUBJECT: GRB 150910A: Swift/UVOT Detection of a Brightening Afterglow
DATE:    15/09/10 16:11:49 GMT
FROM:    Marissa McCaule at PSU  <marissamc@swift.psu.edu>

L. M. McCauley (PSU) and C. Pagani (U Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150910A
154 s after the BAT trigger (Pagani et al., GCN Circ. 18264).
A source consistent with the XRT position
(Pagani et al. GCN Circ. 18264)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  00:22:40.11 =   5.66713 (deg.)
    Dec (J2000) = +33:28:21.9  =  33.47274 (deg.)
with an estimated uncertainty of 0.58 arc sec. (radius, 90% confidence).

Preliminary detections using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) show a very rapid and steep
rise in the luminosity of the afterglow over the first 1 ks of observation.
Further investigation is strongly encouraged.
Preliminary detections for the early exposures are:


Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white                 153            303         147         19.90
white                 156            303         144         19.93
white                 592            612          19         17.09
white                 765            785          19         16.67
white                 866           1016         147         16.30
v                     135            145           9        >17.23
v                     642            662          19         16.64
v                     815            835          19         16.91
v                    1046           1066          19         16.11
b                     568            588          19         17.56
b                     741            761          19         16.87
u                     312            561         245         18.03
u                     312            561         245         18.02
u                     716            736          19         16.14
uvw1                  692            712          19         16.76
uvw2                 1022           1041          19        >17.97

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.05 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB150910A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18271
SUBJECT: GRB 150910A: Enhanced Swift-XRT position
DATE:    15/09/10 19:10:24 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 1428 s of XRT Photon Counting mode data and 5 UVOT
images for GRB 150910A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 5.66723, +33.47278 which is equivalent
to:

RA (J2000): 00h 22m 40.14s
Dec (J2000): +33d 28' 22.0"

with an uncertainty of 1.4 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.


GRB_name: GRB150910A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18272
SUBJECT: GRB 150910A: Swift-XRT refined Analysis
DATE:    15/09/10 22:26:03 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A. Melandri
(INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), D.N. Burrows
(PSU), T.G.R. Roegiers (PSU), L.M. McCauley (PSU) and C. Pagani report
on behalf of the Swift-XRT team:

We have analysed 8.0 ks of XRT data for GRB 150910A (Pagani et al. GCN
Circ. 18264), from 136 s to 35.1 ks after the  BAT trigger. The data
comprise 938 s in Windowed Timing (WT) mode (the first 7 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Evans et
al. (GCN Circ. 18271).

The late-time light curve (from T0+6.4 ks) can be modelled with a
series of power-law decays. The initial decay index is alpha=0.67
(+0.23, -0.21). At T+10.9 ks  the decay steepens to an alpha of 3.17
(+0.86, -0.30) before breaking again at T+20.3 ks to a final decay with
index alpha=1.3 (+/-0.4).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.56 (+/-0.04). The
best-fitting absorption column is  1.30 (+0.16, -0.15) x 10^21 cm^-2,
in excess of the Galactic value of 5.4 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.77 (+0.09, -0.08)
and a best-fitting absorption column of 7.1 (+2.3, -1.7) x 10^20 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 3.7 x 10^-11 (4.2 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      7.1 (+2.3, -1.7) x 10^20 cm^-2
Galactic foreground: 5.4 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:      1.77 (+0.09, -0.08)

If the light curve continues to decay with a power-law decay index of
1.3, the count rate at T+24 hours will be 0.033 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.2 x
10^-12 (1.4 x 10^-12) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00655097.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB150910A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18273
SUBJECT: GRB 150910A: Kast spectroscopy from 3m Shane telescope
DATE:    15/09/11 00:05:09 GMT
FROM:    Weikang Zheng at UC Berkeley  <weikang@berkeley.edu>

WeiKang Zheng, Alexei V. Filippenko and Heechan Yuk (UC Berkeley),
Yinan Zhu (NAOC) and Daniel A. Perley (Dark Cosmology Center)
report on behalf of the KAIT GRB team:

We observed the optical afterglow of GRB 150910A (Pagani et al., 
GCN 18264; Zheng & Filippenko, GCN 18265) with the Kast spectrograph
on the 3m Shane telescope at Lick Observatory, started at 10:08 UT
(about 1.1 hours after the burst), covering the 3500 - 10000 A   
wavelength range. A 1200-second and a 2400-second exposures
were acquired.

The spectrum shows blue continuum flux across the entire spectral
range. We detect absorption lines from Mg II (2796,2803) and Fe II
(2344,2374,2383) at a common redshift of z=1.359, as well as additional
lines further to the blue. We suggest this as the likely redshift of
the GRB.


GRB_name: GRB150910A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18274
SUBJECT: GRB 150910A: Redshift from 10.4m GTC+OSIRIS
DATE:    15/09/11 00:17:10 GMT
FROM:    Antonio de Ugarte Postigo at IAA-CSIC  <deugarte@iaa.es>

Antonio de Ugarte Postigo (IAA-CSIC, DARK/NBI), Christina Thoene (IAA-CSIC), 
Gianluca Lombardi (IAC, ULL, GRANTECAN), and Alberto Perez (GRANTECAN) 
report on behalf of a larger collaboration:

We have observed the afterglow of GRB 150910A (Pagani et al., GCN 18264) 
using the 10.4 m GTC telescope equipped with OSIRIS. Our observation began 
at 23:11 UT (14.1 hr after the burst) and consisted of 3x900s exposures using the 
R1000B grism. The spectrum covers the wavelength range between 3700 and 
7800 AA.

The acquisition image shows the afterglow at a magnitude of r=20.65+/-0.07 as 
compared to SDSS stars.

The first spectrum shows a continuum throughout the full spectral range, with 
several absorption features that correspond to AlII, AlIII, FeII, MgII and MgI at a 
common redshift of 1.360, which we interpret as the redshift of the GRB.


GRB_name: GRB150910A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18275
SUBJECT: GRB 150910A: SAO RAS optical photometry
DATE:    15/09/11 02:06:57 GMT
FROM:    Moskvitin Alexander at SAO RAS  <mosk@sao.ru>

A.S.Moskvitin (SAO RAS), V.P.Goranskij (SAI, Moscow State University),
report on behalf of larger GRB follow-up team:

We observed the field of the GRB 150910A (Pagani et al., GCN #18264)
with the Zeiss-1000, 1-meter telescope of SAO RAS (Russia),
equipped with the broadband filters UBVRcIc and EEV 42-40 CCD.
The observations started since 10.85 hours after the trigger.

We obtained sets of 6 x 300-sec. frames in Rc band three times per
September, 10/11 night. The OT (reported by Pagani et al., GCN #18264;
Zheng & Filippenko, GCN #18265; Dichiara et al., GCN #18266;
Kuroda et al., GCN #18267; Xu et al., GCN #18269; McCauley & Pagani,
GCN #18270; Zheng et al., GCN #18273; de Ugarte Postigo et al.,
GCN #18274) is clearly visible even in single frames.
The results of observations are as following.

#   (T_mid-T0),h   exp.,s     R_mag            time, UT
1.  11.035         6 x 300    20.20 +/- 0.05   19:56:03--20:17:48
2.  13.448         6 x 300    20.57 +/- 0.05   22:15:17--22:48:09
3.  15.739         6 x 300    20.78 +/- 0.05   00:32:30--01:05:46

Photometry is based on nearby SDSS stars (their magnitudes
were converted with the Lupon 2005 equations).


GRB_name: GRB150910A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18276
SUBJECT: GRB 150910A: MITSuME Ishigakijima Optical Observation
DATE:    15/09/11 04:46:31 GMT
FROM:    Daisuke Kuroda at OAO/NAOJ  <dikuroda@oao.nao.ac.jp>

D. Kuroda (OAO, NAOJ),  H. Hanayama, T. Miyaji, J. Watanabe (IAO, NAOJ),
K. Yanagisawa (OAO, NAOJ), S.Nagayama (NAOJ), M. Yoshida (Hiroshima),
K. Ohta (Kyoto) and N. Kawai(Tokyo Tech)
report on behalf of the MITSuME and OISTER collaboration:

We observed the field of GRB 150910A (Pagani et al., GCNC 18264)
with the optical three color (g', Rc and Ic) CCD camera attached
to the Murikabushi 1m telescope of Ishigakijima Astronomical
Observatory.

The observation started on 2015-09-10 12:21:44 UT (~3.3 h after
the burst). We detected the previously reported afterglow (Pagani
et al., GCNC 18264; Zheng and Filippenko, GCNC 18265; Dichiara
et al., GCNC 18266; Kuroda et al., GCNC 18267) in all the three
bands.

Photometric results of the OT are listed below.
We used GSC2.3 catalog for flux calibration.

#T0+[day]  MID-UT    T-EXP[sec]   g'  g'_err  Rc  Rc_err  Ic  Ic_err
-----------------------------------------------------------------------
0.14010    12:26:33     540.0     19.1 0.1    18.8 0.1    18.4 0.1
-----------------------------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]


GRB_name: GRB150910A
Detection_method: GROND
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18277
SUBJECT: GRB 150910A: GROND observation of the afterglow
DATE:    15/09/11 08:30:45 GMT
FROM:    Sebastian Schmidl at TLS Tautenburg  <schmidl@tls-tautenburg.de>

S. Schmidl (TLS Tautenburg), F. Knust, and J. Greiner (both MPE Garching)
report on behalf of the GROND team:

We observed the field of GRB 150910A (SWIFT trigger 655097; Pagani et al,
GCN 18264) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008,
PASP 120, 405) mounted at the 2.2m MPG telescope at ESO La Silla
Observatory (Chile).

Observations started on September 11, 2015, at 05:08 UT, 20.1 hrs after the
GRB trigger. They were performed at an average seeing of 2.8" and at an
average airmass of 2.2.

We clearly detect the optical afterglow reported by Pagani et al. (GCN
18264), Zheng & Filippenko (GCN 18265), Dichiara et al. (GCN 18266),
Kuroda et al. (GCN 18267), Xu et al. (GCN 18269), de Ugarte Postigo et al.
(GCN 18274) and Moskvitin et al (GCN 18275).

Based on total exposures of 7.7 minutes in g'r'i'z'and 4.0 minutes in
JHK, at a midtime of 20.8 hrs after the burst, we measure the following
preliminary magnitudes (AB magnitude system):

g' = 21.5 +/- 0.2 mag,
r' = 21.2 +/- 0.2 mag,
i' = 21.0 +/- 0.2 mag,
z' = 20.8 +/- 0.2 mag,
J  > 19.8 mag,
H  > 19.3 mag, and
K  > 18.1 mag.

Given magnitudes and upper limits are calibrated against SDSS as well as
2MASS field stars and are not corrected for the expected Galactic
foreground extinction corresponding to a reddening of E_(B-V) = 0.05 mag
in the direction of the burst (Schlegel et al. 1998).


GRB_name: GRB150910A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18278
SUBJECT: GRB 150910A: MITSuME Okayama Ks-band Observation
DATE:    15/09/11 09:07:35 GMT
FROM:    Kenshi Yanagisawa at OAO/NAOJ  <yanagi@oao.nao.ac.jp>

Kenshi Yanagisawa, Daisuke Kuroda, Yasuhiro Shimizu, Hideyuki
Izumiura (OAO/NAOJ), Michitoshi Yoshida (Hiroshima-U),
Kouji Ohta(Kyoto-U), and Nobuyuki Kawai(Tokyo Tech.) report
on behalf of the MITSuME collaboration:

We observed the field of GRB150910A (Pagani et al., GCNC 18264)
in Ks-band with a wide-field NIR camera at Okayama Astrophysical
Observatory (Japan). The camera has an effective aperture of 0.91m.

Observations started from 10:03 UT on 10th September, 59 min after
the BAT trigger, to 11:14 UT. The total exposure of 26 min was
successfully obtained.

In our co-add image, we found a single point source at
  R.A.(J2000) = 00:22:39.84
  DEC (J2000) = +33:28:20.5
with an uncertainty of of about 2 arcsec.

We estimate the magnitude Ks = 14.85 +/- 0.13 (Vega).
The calibration was made against 2MASS field stars.

T0+[min]    MID-UT     T-EXP[min]    Ks
------------------------------------------------------------
  +94       10:38        26          14.85 +/- 0.13 (Vega)
------------------------------------------------------------
T0+ : Elapsed time after the burst [min]
T-EXP: Total Exposure time [min]


GRB_name: GRB150910A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18279
SUBJECT: GRB 150910A: NOT observations of the afterglow
DATE:    15/09/11 13:06:31 GMT
FROM:    Zach Cano at U of Iceland  <zewcano@gmail.com>

Z. Cano (U. Iceland), D. Malesani (DARK/NBI), A. de Ugarte Postigo
(IAA-CSIC, DARK/NBI), D. Xu (NAOC/CAS), J. Saario (NOT, U. Turku) and P.
Jakobsson (U. Iceland) report on behalf of a larger collaboration:

We observed the field of GRB 150910A (Pagani et al., GCN Circ. 18264) with
the 2.5-m Nordic Optical Telescope (NOT) equipped with MOSCA in two epochs
on the morning of 11-Sept-2015, at 01:10 and 04:45 UT, respectively.  In
SDSS filters r (epoch 1) and ugrz (epoch 2) we clearly detect the optical
afterglow (e.g. Zheng & Filippenko, GCN Circ. 18265).

A summary of our photometry is as follows:

-------------------------------------------------------
filter (SDSS)        t-t0 (hr)            mag +- merr
-------------------------------------------------------
   r                  16.27              20.85 +- 0.18
   r                  20.18              21.24 +- 0.21
   u                  20.05              21.82 +- 0.24
   g                  20.24              21.49 +- 0.22
   z                  19.84              20.78 +- 0.24

These magnitudes are calibrated to SDSS and are not corrected for
foreground extinction.  We note that these magnitudes are in good agreement
with those obtained by GROND (Schmidl et al., GCN Circ. 18277) at a
contemporaneous post-explosion epoch.  Compared with other datasets, e.g.
Xu et al. (GCN Circ. 18269), our second epoch of r-band observations
implies a power-law like decay in time, e.g. f(t)=t^-alpha, with a decay
slope of alpha=1.
â€‹1.


GRB_name: GRB150911A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18280
SUBJECT: GRB 150911A: Swift detection of a burst
DATE:    15/09/11 18:55:33 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

R. L. C. Starling (U Leicester), S. D. Barthelmy (GSFC),
D. N. Burrows (PSU), V. D'Elia (ASDC), H. A. Krimm (CRESST/GSFC/USRA),
F. E. Marshall (NASA/GSFC), B. Sbarufatti (INAF-OAB/PSU) and
M. H. Siegel (PSU) report on behalf of the Swift Team:

At 18:40:21 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150911A (trigger=655262).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 67.424, +5.743, which is 
   RA(J2000)  =  04h 29m 42s
   Dec(J2000) = +05d 44' 34"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a pair of overlapping peaks
with a total duration of about 12 sec.  The peak count rate
was ~5000 counts/sec (15-350 keV), at ~4 sec after the trigger. 

The XRT began observing the field at 18:41:41.3 UT, 79.9 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 67.4331,
5.7350 which is equivalent to:
   RA(J2000)  = 04h 29m 43.95s
   Dec(J2000) = +05d 44' 05.9"
with an uncertainty of 2.3 arcseconds (radius, 90% containment). This
location is 43 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 1.87
x 10^21 cm^-2 (Willingale et al. 2013). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 82 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
The 8'x8' region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.32. 

Burst Advocate for this burst is R. L. C. Starling (rlcs1 AT star.le.ac.uk). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)


GRB_name: GRB150910A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18281
SUBJECT: GRB 150910A: TSHAO optical observations
DATE:    15/09/11 19:27:21 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

E. Mazaeva (IKI), I. Reva (Fesenkov Astrophysical Institute),   A. 
Kusakin (Fesenkov Astrophysical Institute), A. Volnova (IKI), A. 
Pozanenko  (IKI) report on behalf of larger GRB follow-up collaboration:

We observed the field of GRB 150910A (Pagani et al., GCN  18264)  with 
Zeiss-1000 (East) 1-m telescope of Tien Shan Astronomical Observatory on 
Sep. 10 (UT) 18:02:59 -- 20:37:38.  We obtained several images in R and 
B filters.  In both filters the afterglow  (Pagani et al., GCN 18264; 
Zheng & Filippenko, GCN 18265) is clearly visible. Within 2.5 hours of 
observations we do not detect significant fading of the afterglow. The 
photometry of combined images are following

Date       UT start    t-T0     Filter  Exp.     OT       Err
                        (mid, days)      (s)

2015-09-10 18:08:20    0.42807  R       11*300   20.18 +/- 0.05
2015-09-10 18:02:59    0.42436  B       12*300   20.85 +/- 0.08

The photometry is based on nearby SDSS stars

SDSS_id            R(Lupton)
J002232.47+332751.3    16.29
J002236.24+332854.2    15.92
J002241.61+332836.1    16.23
J002248.33+332723.4    16.76
J002231.90+333004.8    16.93
J002225.39+332809.6    16.12
J002246.76+332716.9    17.63

Our photometry in R-filter is in agreement with  in subsequent 
observations (Moskvitin & Goranskij, GCN 18275).


GRB_name: GRB150911A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18282
SUBJECT: GRB150911A MITSuME Okayama Ks-band upper-limit
DATE:    15/09/11 20:40:22 GMT
FROM:    Kenshi Yanagisawa at OAO/NAOJ  <yanagi@oao.nao.ac.jp>

Kenshi Yanagisawa, Daisuke Kuroda, Yasuhiro Shimizu, Hideyuki Izumiura
(OAO/NAOJ), Michitoshi Yoshida (Hiroshima-U), Kouji Ohta(Kyoto-U)
and Nobuyuki Kawai(Tokyo Tech.) report on behalf of the MITSuME
collaboration:

We observed the field of GRB150911A (Starling et al, GCN18280)
in Ks-band with a wide-field near infrared imager at Okayama
Astrophysical Observatory (Japan).  The imager has effective
aperture of 0.91 m.

Observations started from 18:56 UT on 11th September, just 16 min
after the BAT trigger, to 19:10 UT. The total exposure of 6 min
was successfully obtained.

In our co-add image, we did not find any new point source within
the enhanced XRT error circle (Starling et al, GCN18280) down
to limiting magnitude of Ks=14.3 (Vega, S/N=10) . The photometric
calibration was made against 2MASS field stars.

T0+[s]      MID-UT     T-EXP[sec]      Ks
---------------------------------------------------
 +1380      19:03          375        >14.3
---------------------------------------------------
T0+ : Elapsed time after the burt [sec]
T-EXP: Total Exposure time [sec]


GRB_name: GRB150911A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18283
SUBJECT: GRB 150911A: Enhanced Swift-XRT position
DATE:    15/09/11 21:53:13 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 1481 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 150911A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 67.43406, +5.73533 which is equivalent
to:

RA (J2000): 04h 29m 44.17s
Dec (J2000): +05d 44' 07.2"

with an uncertainty of 1.7 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.


GRB_name: GRB150910A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18284
SUBJECT: GRB 150910A: continued SAO RAS optical observations
DATE:    15/09/11 22:20:23 GMT
FROM:    Moskvitin Alexander at SAO RAS  <mosk@sao.ru>

A. S. Moskvitin (SAO RAS), report on behalf of larger GRB follow-up team:

The field of the GRB 150910A (Pagani et al., GCN #18264) was observed
with the Zeiss-1000 telescope of SAO RAS (Russia) in Rc band
on September, 11.791 (T_mid-T0 = 1.413 days), 17:55:54--20:01:44 UT.

20 x 300 seconds frames were obtained. The OT is still clearly visible
in the stacked image. The brightness of the object R = 22.2 +/- 0.10
(based on the same SDSS stars as in previous circular GCN #18275).


GRB_name: GRB150910A
Detection_method: VLA Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18285
SUBJECT: GRB 150910A: VLA Detection
DATE:    15/09/11 22:54:59 GMT
FROM:    Kate Alexander at Harvard  <kalexander@cfa.harvard.edu>

K. Alexander (Harvard), T. Laskar (NRAO / UC Berkeley), and E. Berger
(Harvard) report on behalf of a larger collaboration:

We observed GRB 150910A (Pagani et al; GCN 18264) at multiple frequencies
with the Karl G. Jansky Very Large Array (VLA) beginning 2015 September
11.10 UT (0.72 days after the burst). At a mean frequency of 9.8 GHz, we
detect a radio source with a preliminary flux density of ~ 0.1 mJy at

RA = 00:22:40.120 +/- 0.021
Dec = +33:28:21.750 +/- 0.036

consistent with the UVOT optical position (McCauley et al; GCN 18270) and
the enhanced Swift/XRT position (Evans et al.; GCN 18271). Follow-up
observations are planned.


GRB_name: GRB150911A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18286
SUBJECT: GRB 150911A: MITSuME Okayama upper limits
DATE:    15/09/12 00:15:46 GMT
FROM:    Daisuke Kuroda at OAO/NAOJ  <dikuroda@oao.nao.ac.jp>

D. Kuroda, K. Yanagisawa, Y. Shimizu, H. Toda (OAO, NAOJ),
S. Nagayama (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto)
and N. Kawai(Tokyo Tech)
report on behalf of MITSuME and OISTER collaboration:

We observed the field of GRB 150911A (Starling et al., GCNC 18280)
with the optical three color (g', Rc and Ic) CCD camera attached
to the MITSuME 50cm telescope of Okayama Astrophysical Observatory.

The observation started on 2015-09-11 18:41:02 UT (~41 sec after the burst).
We did not find any new point source within the enhanced XRT circle
(Goad et al., GCNC 18283) in all the three bands.

Three sigma upper limits of the OT are listed below.
We used GSC2.3 catalog for flux calibration.

#T0+[day]  MID-UT    T-EXP[sec]   g'     Rc     Ic
-----------------------------------------------------
0.01168    18:57:10    1380.0   >20.2  >19.5  >19.1
-----------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]


GRB_name: GRB150910A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18287
SUBJECT: GRB 150910A: Chuguev observatory optical observations
DATE:    15/09/12 02:51:11 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

Yu. Krugly (IA KhNU),  E. Mazaeva (IKI), V. Shevchenko  (IA KhNU),  T. 
Gromakina (IA KhNU), I. Molotov (KIAM), A. Pozanenko  (IKI) report on 
behalf of larger GRB follow-up collaboration:

We observed the field of GRB 150910A (Pagani et al., GCN  18264)  with 
0.7m  telescope of Institute of Astronomy, Kharkiv National University 
starting on Sep. 10 (UT) 21:41:15. We obtained several images in R B 
filter.   The afterglow  (Pagani et al., GCN 18264; Zheng & Filippenko, 
GCN 18265) is clearly visible in a combined image. The photometry of the 
combined image is following

Date       UT start    t-T0     Filter  Exp.     OT       Err
                        (mid, days)      (s)

2015-09-10 21:41:15    0.52235  R       11*180   20.25 +/-0.14

The photometry is based on SDSS stars used in GCN 18281 (Mazaeva et al.)


GRB_name: GRB150910A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18288
SUBJECT: GRB 150910A: MITSuME Ishigakijima Optical Observation after 1 day
DATE:    15/09/12 02:51:13 GMT
FROM:    Daisuke Kuroda at OAO/NAOJ  <dikuroda@oao.nao.ac.jp>

D. Kuroda (OAO, NAOJ),  H. Hanayama, T. Miyaji, J. Watanabe (IAO, NAOJ),
K. Yanagisawa (OAO, NAOJ), S.Nagayama (NAOJ), M. Yoshida (Hiroshima),
K. Ohta (Kyoto) and N. Kawai(Tokyo Tech)
report on behalf of the MITSuME and OISTER collaboration:

We observed the field of GRB 150910A (Pagani et al., GCNC 18264)
with the optical three color (g', Rc and Ic) CCD camera attached
to the Murikabushi 1m telescope of Ishigakijima Astronomical
Observatory.

The observation started on 2015-09-11 12:29:42 UT (~1.14 days after
the burst). We detected the previously reported afterglow (Pagani
et al., GCNC 18264; Zheng and Filippenko, GCNC 18265; Dichiara
et al., GCNC 18266; Kuroda et al., GCNC 18267) in g' and Rc bands.

Photometric results and three sigma upper limit of the OT are listed below.
We used GSC2.3 catalog for flux calibration.

#T0+[day]  MID-UT    T-EXP[sec]   g'  g'_err  Rc  Rc_err  Ic  Ic_err                                                                    
-----------------------------------------------------------------------
1.21526    14:14:46    4800.0     21.8 0.2    21.2 0.2    >20.8
-----------------------------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]


GRB_name: GRB150910A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18289
SUBJECT: GRB 150910A: AAO optical observations
DATE:    15/09/12 03:14:23 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

E. Mazaeva (IKI), R. Inasaridze (AAO), V. Zhuzhunadze (AAO), I. Molotov 
(KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up 
collaboration:

We observed the field of GRB 150910A (Pagani et al., GCN  18264)  with 
  with AS-32 (0.7m) telescope of Abastumani Observatory starting on Sep. 
10 (UT) 18:53:54. We obtained several unfiltered images. The afterglow 
(Pagani et al., GCN 18264; Zheng & Filippenko, GCN 18265) is clearly 
visible in a combined image. The photometry of the combined image is 
following

Date       UT start    t-T0     Filter  Exp.     OT       Err
                        (mid, days)      (s)

2015-09-10 18:53:54    0.45834  none    50*120   20.16 +/- 0.06

The photometry is based on SDSS stars used in GCN 18281 (Mazaeva et al.)


GRB_name: GRB150911A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18290
SUBJECT: GRB 150911A: Swift-XRT refined Analysis
DATE:    15/09/12 06:55:05 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

C. Pagani (U. Leicester), A.P. Beardmore (U. Leicester), P. D'Avanzo
(INAF-OAB), V. D'Elia (ASDC), A. D'ai (INAF-IASFPA), T.G.R. Roegiers
(PSU), L.M. McCauley (PSU), J.A. Kennea (PSU), P.A. Evans (U.
Leicester) and R.L.C. Starling report on behalf of the Swift-XRT team:

We have analysed 10 ks of XRT data for GRB 150911A (Starling et al. GCN
Circ. 18280), from 65 s to 23.7 ks after the  BAT trigger. The data
comprise 114 s in Windowed Timing (WT) mode (the first 7 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Goad et al.
(GCN Circ. 18283).

The late-time light curve (from T0+4.9 ks) can be modelled with a
power-law decay with a decay index of alpha=1.81 (+0.14, -0.13).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.58 (+0.11, -0.10). The
best-fitting absorption column is  2.7 (+0.6, -0.5) x 10^21 cm^-2, in
excess of the Galactic value of 1.9 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.96 (+0.14, -0.13)
and a best-fitting absorption column of 4.1 (+/-0.7) x 10^21 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 4.0 x 10^-11 (6.1 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      4.1 (+/-0.7) x 10^21 cm^-2
Galactic foreground: 1.9 x 10^21 cm^-2
Excess significance: 5.4 sigma
Photon index:      1.96 (+0.14, -0.13)

If the light curve continues to decay with a power-law decay index of
1.81, the count rate at T+24 hours will be 2.0 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.2 x
10^-14 (1.3 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00655262.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB150912A
Detection_method: INTEGRAL
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18291
SUBJECT: GRB 150912A: A long GRB detected by INTEGRAL
DATE:    15/09/12 11:39:08 GMT
FROM:    Sandro Mereghetti at IASF/CNR  <sandro@iasf-milano.inaf.it>

S.Mereghetti (IASF-Milano), D.Gotz (CEA, Saclay), E.Bozzo, C.Ferrigno, 
L.Ducci (ISDC, Versoix), and J.Borkowski (CAMK, Torun) on behalf of the 
IBAS Localization Team report:

a gamma ray burst lasting about 30 s has been detected by IBAS in the 
IBIS/ISGRI data at 10:37:30 UT of 2015 September 12.

The refined coordinates (J2000) are:

R.A.= 248.4435 deg
DEC.= -21.03376  deg

with an uncertainty of   2  arcmin (90% c.l.).

The burst had a peak flux of about 1.5 counts/cm2/s (20-200 keV, 1-s 
integration time) and a fluence in the same energy range of about 1e-6 
erg/cmq.

A plot of the light curve will  be posted at
http://ibas.iasf-milano.inaf.it/IBAS_Results.html


GRB_name: GRB150911A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18292
SUBJECT: GRB 150911A: Swift-BAT refined analysis
DATE:    15/09/12 14:47:18 GMT
FROM:    Tilan Ukwatta at LANL  <tilan.ukwatta@gmail.com>

C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC),
J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC),
D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU), R. L. C. Starling (U Leicester),
T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-240 to T+962 sec from the recent telemetry
downlink,
we report further analysis of BAT GRB 150911A (trigger #655262)
(Starling, et al., GCN Circ. 18280). The BAT ground-calculated position is
RA, Dec = 67.428, 5.731 deg which is
   RA(J2000)  =  04h 29m 42.6s
   Dec(J2000) = +05d 43' 50.2"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 67%.

The mask-weighted light curve shows a broad peak starting around
T-2 sec and ending around T+10 sec. T90 (15-350 keV) is
T90 (15-350 keV) is 7.2 +- 0.6 sec (estimated error including systematics).

The time-averaged spectrum from T-1.04 to T+9.61 sec is best fit by a power
law
with an exponential cutoff.  This fit gives a photon index 1.02 +- 0.26,
and Epeak of 51.6 +- 3.8 keV (chi squared 52.34 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 2.1 +- 0.1 x 10^-06
erg/cm2
and the 1-sec peak flux measured from T+3.90 sec in the 15-150 keV band is
5.2 +- 0.3 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.93 +- 0.05 (chi squared 97.49 for 57 d.o.f.).  All the quoted errors
are at the 90% confidence level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/655262/BA/


GRB_name: GRB150911A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18293
SUBJECT: GRB 150911A: Swift/UVOT Upper Limits
DATE:    15/09/12 15:18:00 GMT
FROM:    Frank Marshall at GSFC  <femarsha@khamseen.gsfc.nasa.gov>

GRB 150911A: Swift/UVOT Upper Limits

F. E. Marshall (NASA/GSFC) and R. L. C. Starling (U. Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150911A
82 s after the BAT trigger (Starling et al., GCN Circ. 18280).
No optical afterglow consistent with the enhanced XRT position
(Goad et al. GCN Circ. 18283) is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC            82          232          147         >20.6
u_FC               294          544          246         >20.2
white               82         1702          400         >21.2
v                  623         1590          117         >18.9
b                  549         1689          117         >19.4
u                  294         1665          343         >20.4
w1                 673         1640          117         >19.1
w2                 772         1565           97         >19.5

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.32 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB150911A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18294
SUBJECT: GRB150911A: P60 Observations
DATE:    15/09/12 15:24:56 GMT
FROM:    S. Bradley Cenko at NASA/GSFC  <brad.cenko@nasa.gov>

S. B. Cenko (NASA/GSFC) and D. A. Perley (DARK) report on behalf of a larger collaboration:

We observed the location of GRB150911A (Starling et al., GCN 18280) with the robotic Palomar 60-inch telescope.  Observations were obtained in the r', i', and z' filters beginning at 09:03 UT on 2015 Sep 12 (dt ~ 14.4 hours after the Swift trigger).  In stacked images we do not detect any sources within the enhanced XRT error circle (Goad et al., GCN 18283) in any filter.  Using comparison point sources from the USNO-B1 catalog for reference, we calculate a limiting magnitude of R > 22.5 in a stacked image at a median time of 09:46 UT on 2015 Sep 12.


GRB_name: GRB150910A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18295
SUBJECT: GRB150910A: P60 Observations
DATE:    15/09/12 16:15:10 GMT
FROM:    Daniel Perley at Caltech  <dperley@astro.caltech.edu>

D. A. Perley (DARK) and S. B. Cenko (NASA/GSFC) report:

We observed the location of GRB 150910A (Pagani et al., GCN 18264) using 
the robotic Palomar 60-inch telescope on two epochs during the night of 
2015-09-11 UT, and an additional epoch during the night of 2015-09-12 
UT.  During each epoch we acquired 3x180s of imaging in each of the g', 
r', and i' filters.

The optical afterglow (Pagani et al.; Zheng and Filippenko, GCN 18265) 
is detected in each observation.  Preliminary photometry relative to 
SDSS yields:

t_start(d)  filt   mag      emag
    0.973    i  =  21.24 +/- 0.12
    0.980    g  =  21.54 +/- 0.06
    0.989    r  =  21.35 +/- 0.08
    1.067    i  =  21.28 +/- 0.07
    1.074    g  =  21.85 +/- 0.06
    1.081    r  =  21.50 +/- 0.06
    2.060    i  =  22.21 +/- 0.17
    2.067    g  =  22.66 +/- 0.14
    2.074    r  =  23.03 +/- 0.26


GRB_name: GRB150906B
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18296
SUBJECT: GRB 150906B: theoretical estimation of redshift and isotropic energy
DATE:    15/09/12 19:09:18 GMT
FROM:    Remo Rufinni at ICRA  <ruffini@icra.it>

R. Ruffini, C.L. Bianco, M. Enderli, M. Kovacevic, L. Li, M. Muccino, R. Moradi, G.B. Pisani, J.A. Rueda, Y. Wang report:

In the GCN 18263 (Levan et al. 2015), the galaxy NGC 3313 (z=0.0124, d=54 Mpc), which lies within the detection horizon of Advanced-LIGO/VIRGO, is presumed to be the host galaxy of GRB 150906B. Consequently, the isotropic energy of GRB 150906B is inferred Eiso~10^{49} erg. In the GCN 18259 (Golenetskii et al., 2015) from Konus-Wind, the time-averaged spectrum of GRB 150906B fitted by a cutoff power law gives the peak energy Ep = 928(-95,+111) keV in the observer's frame.

From previous GRB statistics (see attached figure [1] and ref. [2]), a typical short GRB with Ep~1 MeV corresponds to Eiso~10^{51} erg. With a fluence of 2.8(-0.2,+0.2)x10^{-5} erg/cm2 from GCN 18259, the redshift of GRB 150906B is expected to be z > 0.06 (266 Mpc), most probably z~0.12 (555 Mpc). Therefore the host galaxy of GRB 150906B could be one of the others nearby.

This type of short GRBs with Eiso < 10^{52} erg originate from merging neutron stars (NSs) leading to a massive NS and not to a black hole [3]. In view of the small value of the energetic, we indicate these sources as short gamma-ray flash (SGRF). As opposed to the more energetic short gamma-ray bursts, the SGRFs never have GeV emission.


 [1] The MuRuWaZha Ep-Eiso relation: <http://www.icranet.org/documents/MuRuWaZha.pdf>
 [2] Zhang, F.-W., Shao, L., Yan, J.-Z., et al. 2012, ApJ 750, 88
 [3] Ruffini, R., Muccino, M., Kovacevic., et al. 2015 ApJ 808, 190


GRB_name: GRB150912A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18297
SUBJECT: GRB 150912A: Swift ToO observations
DATE:    15/09/12 19:40:14 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a ToO observation of the INTEGRAL GRB 150912A. 
Automated analysis of the XRT data will be presented online at
http://www.swift.ac.uk/ToO_GRBs/00020557

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the INTEGRAL event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a 
GCN Circular after manual consideration.

Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).

This circular is an official product of the Swift-XRT team.


GRB_name: GRB150906B
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18298
SUBJECT: GRB 150906B - NGC 3313 association: Constraints from Ep-Eiso and Ep-Liso Relations
DATE:    15/09/12 19:47:57 GMT
FROM:    Binbin Zhang at UAH  <binbin.zhang@uah.edu>

Fu-Wen Zhang (UNLV/GULT), Binbin Zhang (UAH) and Bing Zhang (UNLV) report:

GRB 150906B was observed by Konus-Wind as a typical short, bright and
spectrally hard burst with Ep=928(-95,+111) keV (Golenetskii et al.
GCN 18259). It was suggested (Levan et al. GCN 18263) that it may be
associated with NGC 3313 (z=0.0124, d=54 Mpc) with an offset = 130
kpc. Using the flux/fluence and spectral information of Golenetskii et
al. GCN 18259, we plot GRB 150906B in the E_p-Eiso (Fig1) and E_p-Liso
(Fig 2) diagrams and compare it with other short and long GRBs. We
found that GRB 150906B would be a significant outlier of both
relations if it had occurred at redshift = 0.01. So if the burst is
indeed within the aLIGO horizon, it must be very different from most
short GRBs we observe. If one believes this burst is a typical GRB,
then it would have a redshift in the range of ~0.1 to 1.0.  We note
that Ruffini et al. (GCN 18296) reached a similar conclusion
independently.

Fig1: http://104.167.114.70/gcns/grb150906b/fig1.png
Fig2: http://104.167.114.70/gcns/grb150906b/fig2.png


GRB_name: GRB150912A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18299
SUBJECT: GRB 150912A: Fermi GBM observation
DATE:    15/09/12 21:34:34 GMT
FROM:    Elisabetta Bissaldi at U.Innsbruk/IAPP  <Elisabetta.Bissaldi@uibk.ac.at>

E. Bissaldi (INFN Bari) reports on behalf of the Fermi GBM Team:


"At 10:37:38.70 UT on 12 September 2015, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 150912A (trigger 463747062/150912443),
which was also detected by INTEGRAL (Mereghetti et al. 2015, GCN 18291).
The GBM on-ground location is consistent with the INTEGRAL position.

The angle from the Fermi-LAT boresight at the GBM trigger time is 67 degrees.

The GBM light curve consists of a single peak
with a duration (T90) of about 30 s (50-300 keV).
The time-averaged spectrum from T0-6 s to T0+22 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -1.11 +/- 0.10 and
the cutoff energy, parameterized as Epeak, is 250 +/- 40 keV.

The event fluence (10-1000 keV) in this time interval is
(4.5 +/- 0.3)E-06 erg/cm^2. The 1-sec peak photon flux, measured
starting from T0+2.2 s in the 10-1000 keV band,
is 2.82 +/- 0.25 ph/s/cm^2.


The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."


GRB_name: GRB150912A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18300
SUBJECT: GRB 150912A: MASTER-IAC optical observations 
DATE:    15/09/12 22:30:37 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres
The Instituto de Astrofisica de Canarias

V. Lipunov, E. Gorbovskoy,  N.Tyurina, V.Kornilov,
P.Balanutsa, A.Kuznetsov, D.Kuvshinov, E.Popova
Lomonosov Moscow State University, Sternberg Astronomical Institute

K.Ivanov, O.Gres, N.M.Budnev, S.Yazev,
Irkutsk State University

D.Buckley, S. Potter, A.Kniazev, M.Kotze
South African Astronomical Observatory

A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik
Kislovodsk Solar Station of the Pulkovo Observatory

V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov, A.Gabovich
Blagoveschensk Educational State University, Blagoveschensk

V.Krushinski, I.Zalozhnih
Ural Federal University, Kourovka

Hugo Levato and Carlos Saffe
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)

Claudio Mallamaci, Carlos Lopez and Federico Podest
Observatorio Astronomico Felix Aguilar (OAFA)

MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in IAC  was pointed to the  GRB150912A 33865 sec (9.4 h) after 
trigger time at 2015-09-12 20:01:55 UT directly after the sunset. On our 
first single and coadd sets we haven't found optical transient  within IPN 
error-box (Mereghetti et. al GCN 18291).
The 5-sigma upper limit has been about 19.2 on single (180 sec) and ~ 20.3 
at coadd (10x180 sec) images.
The message may be cited.


GRB_name: GRB150910A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18301
SUBJECT: GRB 150910A: MITSuME Ishigakijima Optical Observation after 2 days
DATE:    15/09/13 00:03:14 GMT
FROM:    Daisuke Kuroda at OAO/NAOJ  <dikuroda@oao.nao.ac.jp>

D. Kuroda (OAO, NAOJ),  H. Hanayama, T. Miyaji, J. Watanabe (IAO, NAOJ),
K. Yanagisawa (OAO, NAOJ), S.Nagayama (NAOJ), M. Yoshida (Hiroshima),
K. Ohta (Kyoto) and N. Kawai(Tokyo Tech)
report on behalf of the MITSuME and OISTER collaboration:

We observed the field of GRB 150910A (Pagani et al., GCNC 18264)
with the optical three color (g', Rc and Ic) CCD camera attached
to the Murikabushi 1m telescope of Ishigakijima Astronomical
Observatory.

The observation started on 2015-09-12 13:59:26 UT (~2.2 days after
the burst). We detected the previously reported afterglow (Pagani
et al., GCNC 18264; Zheng and Filippenko, GCNC 18265; Dichiara
et al., GCNC 18266; Kuroda et al., GCNC 18267) in Rc band.

Photometric results and three sigma upper limit of the OT are listed below.
We used GSC2.3 catalog for flux calibration.

#T0+[day]  MID-UT    T-EXP[sec]   g'     Rc  Rc_err  Ic
-----------------------------------------------------------------------
2.22658    14:31:04    3240.0    >22.4   22.3 0.4   >20.73
-----------------------------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]


GRB_name: GRB150910A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18302
SUBJECT: GRB 150910A: RATIR Observations
DATE:    15/09/13 16:22:24 GMT
FROM:    Nat Butler at UC berkeley  <natxbutler@gmail.com>

Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (UCB), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (GSFC/STScI), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jos A. de Diego (UNAM), Leonid Georgiev (UNAM), Jess Gonzlez (UNAM), Carlos Romn-Ziga (UNAM), Neil Gehrels (GSFC), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (ASU), and Vicki Toy (UMD) report:

We observed the field of GRB 150910A (Pagani et al., GCN 18264) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astronmico Nacional on Sierra San Pedro Mrtir from 2015/09 13.15 to 2015/09 13.26 UTC (66.44 to 69.21 hours after the BAT trigger), obtaining a total of 0.99 hours exposure in the r, i, and z bands.

The optical afterglow (Pagani et al.; Zheng and Filippenko, GCN 18265) is well detected.  In comparison with the SDSS DR9 catalog, we obtain:

   r 22.44 +/- 0.13
   i 22.31 +/- 0.11
   z > 20.29 (3-sigma)

These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB.

We thank the staff of the Observatorio Astronmico Nacional in San Pedro Mrtir.


GRB_name: GRB150911A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18303
SUBJECT: GRB 150911A: WHT optical imaging
DATE:    15/09/13 20:49:33 GMT
FROM:    Nial Tanvir at U.Leicester  <nrt3@star.le.ac.uk>

N. R. Tanvir, K. Wiersema (U. Leicester), A. J. Levan (U. Warwick),
F. Riddick (ING), C. Bergfors (UCL) report on behalf of a larger collaboration:

We observed the position of GRB 150911A (Starling et al. GCN 18280), using the ACAM instrument on the 4.2m William Herschel Telescope (La Palma, Spain).  We acquired imaging in Sloan r, i and z bands, with midpoint 03:46 UT on 12 September 2015 (i.e. 8.9 hours after burst). Data consist of 4x300 seconds exposure time in each filter. No sources are detected within the XRT enhanced position error circle (Goad et al. GCN 18283). Just outside the XRT error circle are two faint sources, detected in all filters:

Source 1  at  RA, Dec = 04:29:44.279, +5:44:08.52
Source 2 at   RA, Dec = 04:29:44.120, +5:44:04.34

We note that source 1 is slightly extended and provisional photometric calibration gives magnitude r=24.1.  Source 2 appears point-like with magnitude r=25.2.

A second epoch observation would be required to ascertain which if any of these sources is associated with the GRB.


GRB_name: GRB150912A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18304
SUBJECT: GRB 150912A: MITSuME Ishigakijima upper limits
DATE:    15/09/14 00:44:10 GMT
FROM:    Daisuke Kuroda at OAO/NAOJ  <dikuroda@oao.nao.ac.jp>

D. Kuroda (OAO, NAOJ),  H. Hanayama, T. Miyaji, J. Watanabe (IAO, NAOJ),
K. Yanagisawa (OAO, NAOJ), S.Nagayama (NAOJ), M. Yoshida (Hiroshima),
K. Ohta (Kyoto) and N. Kawai(Tokyo Tech)
report on behalf of the MITSuME and OISTER collaboration:

We observed the field of GRB 150912A (Mereghetti et al., GCNC 18291)
with the optical three color (g', Rc and Ic) CCD camera attached
to the Murikabushi 1m telescope of Ishigakijima Astronomical
Observatory.

The observation started on 2015-09-12 12:15:39 UT (~1.6 h after the burst).
We did not find any new point source within the INTEGRAL-IBAS error circle
(Mereghetti et al., GCNC 18291) in all the three bands.

Three sigma upper limits of the OT are listed below.
We used GSC2.3 catalog for flux calibration.

#T0+[day]  MID-UT    T-EXP[sec]   g'     Rc     Ic
-----------------------------------------------------
0.07014    12:18:30     300.0   >19.7  >19.4  >18.6
-----------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]


GRB_name: GRB150910A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18306
SUBJECT: GRB 150910A: Mt. Terskol observatory optical observation
DATE:    15/09/14 07:16:41 GMT
FROM:    Alexei Pozanenko at IKI  <alex@grb.rssi.ru>

M. Andreev (Terskol Branch of INASAN), E. Mazaeva (IKI), A. Sergeev (Terskol Branch of INASAN), A. Volnova (IKI), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:

We observed the field of GRB 150910A (Pagani et al., GCN 18264) with Zeiss-600 telescope of Mt. Terskol observatory in R-filter starting on Sep. 10 (UT) 20:45:05. We obtained several unfiltered images. The afterglow (Pagani et al., GCN 18264; Zheng & Filippenko, GCN 18265) is clearly detected in a combined image. The photometry of the combined image is following

Date UT start t-T0 Filter Exp. OT Err
(mid, days) (s)

2015-09-10 20:45:05 0.51974 R 46*120 20.46 +/- 0.07

The photometry is based on SDSS stars used in GCN 18281 (Mazaeva et al.) 


GRB_name: GRB150911A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18307
SUBJECT: GRB 150911A:   Khureltogot upper limit
DATE:    15/09/14 07:20:31 GMT
FROM:    Alexei Pozanenko at IKI  <alex@grb.rssi.ru>

E. Mazaeva (IKI), S. Schmalz (AIP), N. Tungalag (Research Center of Astronomy and Geophysics MAS), A. Volnova (IKI), I.Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:

We observed the field of GRB 150911A (Starling et al., GCN 18280) with ORI-40 telescope of Khureltogot observatory starting on Sep., 11 (UT) 19:03:00, i.e. ~23 minutes after the burst trigger. We do not detect any object within enhanced XRT error circle (Goad et al., GCN 18283). Photometry of the field is following


Date UT start       t-T0   Filter Exp.  Upper_Limit (3sigma)
                    (mid, days) (s)

2015-09-11 19:03:00 0.0351 none   45*60 20.9

Photometry is base on nearby USNO-B.1 stars
USNO-B.1_id R2
0957-0043966 15.54
0957-0043954 16.24
0957-0043961 16.45


GRB_name: GRB150911A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18308
SUBJECT: GRB 150911A: Mt. Terskol observatory upper limit
DATE:    15/09/14 07:27:05 GMT
FROM:    Alexei Pozanenko at IKI  <alex@grb.rssi.ru>

M. Andreev (Terskol Branch of INASAN), E. Mazaeva (IKI), A. Sergeev (Terskol Branch of INASAN), A. Volnova (IKI), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:

We observed the field of GRB 150911A (Starling et al., GCN 18280) with Zeiss-600 telescope of Mt. Terskol observatory in R-filter starting on Sep. 11 (UT) 23:26:40. We do not detect any object within enhanced XRT error circle (Goad et al., GCN 18283). Photometry of the field is following

Date UT start        t-T0 Filter Exp.   Upper_Limit (3sigma)
                     (mid, days) (s)

2015-09-11 23:26:40 0.2273 R     40*120 21.7

Photometry is based on nearby USNO-B.1 stars
USNO-B.1_id R2
0957-0043966 15.54
0957-0043954 16.24
0957-0043961 16.45


GRB_name: GRB150911A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18309
SUBJECT: GRB 150911A: Chuguev observatory upper limit
DATE:    15/09/14 08:47:21 GMT
FROM:    Alexei Pozanenko at IKI  <alex@grb.rssi.ru>

Yu. Krugly (IA KhNU), V. Shevchenko (IA KhNU), T. Gromakina (IA KhNU), I. Molotov (KIAM), E. Mazaeva (IKI), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:

We observed the field of GRB 150911A (Starling et al., GCN 18280) with 0.7m telescope of Institute of Astronomy, Kharkiv National University starting on Sep. 12 (UT) 01:07:23. We do not detect any object within enhanced XRT error circle (Goad et al., GCN 18283). Photometry of the field is following


Date UT start       t-T0   Filter Exp.   Upper_Limit (3sigma)
                    (mid, days)  (s)

2015-09-12 01:07:23 0.2804 R      11*180 20.8

Photometry is based on nearby USNO-B.1 stars
USNO-B.1_id R2
0957-0043966 15.54
0957-0043954 16.24
0957-0043961 16.45


GRB_name: GRB150912A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18310
SUBJECT: GRB 150912A: Swift-XRT and UVOT observations
DATE:    15/09/14 13:38:28 GMT
FROM:    Kim Page at U.of Leicester  <klp5@leicester.ac.uk>

K.L. Page (U. Leicester), M. H. Siegel (PSU) and P.A. Evans (U.
Leicester) report on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the INTEGRAL-detected
burst GRB 150912A (Mereghetti et al. GCN Circ. 18291), collecting 4.7
ks of Photon Counting (PC) mode data between T0+32.6 ks and T0+50.4 ks.


No X-ray sources have been detected inside or close to the INTEGRAL
error region. The 3-sigma upper limit in the field ranges from ~0.002
to ~0.004 ct s^-1, corresponding to a 0.3-10 keV observed flux of
9.0e-14 to 1.5e-13 erg cm^-2 s^-1 (assuming a typical GRB spectrum).

Two uncatalogued sources were detected too far from the GRB position to
be likely afterglow candidates.

The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
http://www.swift.ac.uk/ToO_GRBs/00020557.

Swift-UVOT also began settled observations of the field of GRB 150912A
32.6 ks after the INTEGRAL trigger. No optical afterglow consistent
with the INTEGRAL position is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial
exposures are:

Filter        T_start(s)   T_stop(s)    Exp(s)   Mag

w2   32643       50446     4789  >21.2

The magnitudes in the table are not corrected for the Galactic
extinction due to the reddening of E(B-V) = 0.42 in the direction of
the burst (Schlegel et al. 1998).

This circular is an official product of the Swift-XRT and UVOT teams.


GRB_name: GRB150907A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18311
SUBJECT: GRB 150907A: Swift-XRT afterglow detection
DATE:    15/09/14 16:02:36 GMT
FROM:    Boris Sbarufatti at INAF-OAB/IASFPA  <boris.sbarufatti@brera.inaf.it>

J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), J.P. Osborne (U.
Leicester), K.L. Page (U. Leicester), A. D'ai (INAF-IASFPA), A. Maselli
 (INAF-IASFPA), A. Melandri (INAF-OAB), D.N. Burrows (PSU) and P.A.
Evans (U. Leicester) report on behalf of the Swift-XRT team:

Swift-XRT has conducted further observations of the field of the
MAXI-detected burst GRB 150907A (Nakagawa et al. GCN Circ. 18246). The
observations now extend from T0+8.8 ks to T0+489.4 ks. The source
previously reported by Kennea et al. (GCN Circ. 18250), "Source 1", is
fading with 3-sigma significance, and is therefore likely the GRB
afterglow.  The position of this source is RA, Dec=225.0528, -47.7080
which is equivalent to:

RA (J2000): 15:00:12.68
Dec(J2000): -47:42:28.8

with an uncertainty of 6.8 arcsec (radius, 90% confidence).  This
position is 10.9 arcmin from the MAXI position.  The source is fading
with alpha >0.5.

The results of the XRT-team automatic analysis of the likely afterglow
are at http://www.swift.ac.uk/xrt_products/TILED_GRB00048/index_1.php.
The results of the full analysis of the tiled XRT observations are
available at http://www.swift.ac.uk/xrt_products/TILED_GRB00048.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB150910A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18312
SUBJECT: GRB 150910A: Continued RATIR Observations
DATE:    15/09/14 17:25:20 GMT
FROM:    Nat Butler at UC berkeley  <natxbutler@gmail.com>

Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (UCB), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (GSFC/STScI), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jos A. de Diego (UNAM), Leonid Georgiev (UNAM), Jess Gonzlez (UNAM), Carlos Romn-Ziga (UNAM), Neil Gehrels (GSFC), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (ASU), and Vicki Toy (UMD) report:

We observed the field of GRB 150910A (Pagani et al., GCN 18264) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astronmico Nacional on Sierra San Pedro Mrtir from 2015/09 14.17 to 2015/09 14.46 UTC (90.88 to 98.01 hours after the BAT trigger), obtaining a total of 1.71 hours exposure in the r, i, and z bands.

The optical afterglow (Pagani et al.; Zheng and Filippenko, GCN 18265) is well detected.  In comparison with the SDSS DR9 catalog, we obtain:

   r = 22.23 +/- 0.09
   i = 22.44 +/- 0.10
   z > 19.89 (3-sigma)

These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB.  Compared to our previous night of observations (Butler et al., GCN 18302), the source flux is consistent with remaining constant at the ~1-sigma level.  Also, the source appears to be extended in our images, suggesting that the flux may be dominated by the GRB host galaxy.

We thank the staff of the Observatorio Astronmico Nacional in San Pedro 
Mrtir.


GRB_name: GRB150911A
Detection_method: GROND
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18313
SUBJECT: GRB 150911A: GROND Upper Limits
DATE:    15/09/14 18:14:04 GMT
FROM:    Sebastian Schmidl at TLS Tautenburg  <schmidl@tls-tautenburg.de>

S. Schmidl (TLS Tautenburg), F. Knust, and J. Greiner (both MPE Garching)
report on behalf of the GROND team:

We observed the field of GRB 150911A (Swift trigger 655262; Starling et
al, GCN 18280) simultaneously in g'r'i'z'JHK with GROND (Greiner et al.
2008,PASP 120, 405) mounted at the 2.2m MPG telescope at ESO La Silla
Observatory (Chile).

Observations started on September 12, 2015, at 05:59 UT, 11.3 hrs after
the GRB trigger. They were performed at an average seeing of 2.2" and at an
average airmass of 1.8.

We do not detect a source within the 1.7" Swift-XRT error circle
reported by Goad et al. (GCN 18283).

Based on total exposures of 33 minutes in g'r'i'z'and 43 minutes in
JHK, at a midtime of 12.1 hrs after the burst, we measure the following
preliminary upper limits (AB magnitude system):

g'> 24.1 mag,
r'> 23.8 mag,
i'> 23.2 mag,
z'> 22.8 mag,
J > 21.6 mag,
H > 21.0 mag, and
K > 19.9 mag.

Given upper limits are calibrated against GROND zeropoints as well as
2MASS field stars and are not corrected for the expected Galactic
foreground extinction corresponding to a reddening of E_(B-V) = 0.32 mag
in the direction of the burst (Schlegel et al. 1998).


GRB_name: GRB150910A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18314
SUBJECT: GRB 150910A: T100 observations
DATE:    15/09/15 08:24:52 GMT
FROM:    Eda Sonbas at NASA/GSFC  <edasonbas@gmail.com>

E. Sonbas (Adiyaman Univ.), O. Basturk (Ankara Univ.), T. Guver (Istanbul
Univ.), E. Gogus (Sabanci Univ.), S. Eryilmaz, O. Erece, H. Kirbiyik (TUG)
report on behalf of a larger collaboration


We observed the field of Swift GRB 150910A (Pagani et al., GCN#18264) with
the 1.0 meter T100 telescope (Bakirlitepe, TUBITAK National Observatory,
Turkey), starting September, 10, 20:08:16 UT (~ 11 hours after the
trigger). Observations were carried out in the R filter. The afterglow is
detected in the R band images with an exposure time of 300 s.


Using USNO-B1 star USNO-B1 1234-0008068 (R.A.=5.65, Dec=+33.45) in the
field, the magnitudes of the OT were estimated as follows;


t-t0 (hr) exp.(s) filt mag err (+/-)

10.97 300 R 20.09 0.23

11.06 300 R 20.18 0.25


Analysis of further observations with the same filter is ongoing.


We thank to TUBITAK National Observatory for a partial support in using
T100 telescope with project number 10CT100-95 and technical support.


GRB_name: GRB150915A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18315
SUBJECT: GRB 150915A: Swift detection of a burst
DATE:    15/09/15 21:37:16 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

V. D'Elia (ASDC), N. Gehrels (NASA/GSFC), L. Izzo (URoma/ICRA),
F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL) and M. H. Siegel (PSU)
report on behalf of the Swift Team:

At 21:18:24 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150915A (trigger=655721).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 319.731, -34.854 which is 
   RA(J2000) = 21h 18m 55s
   Dec(J2000) = -34d 51' 12"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is usual for an image trigger, there
is no obvious variation in the immediately available BAT lightcurve. 

The XRT began observing the field at 21:20:33.5 UT, 128.7 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source located at RA, Dec 319.65874,
-34.91306 which is equivalent to:
   RA(J2000)  = 21h 18m 38.10s
   Dec(J2000) = -34d 54' 47.0"
with an uncertainty of 3.6 arcseconds (radius, 90% containment). This
location is 301 arcseconds from the BAT onboard position. This position
may be improved as more data are received; the latest position is
available at http://www.swift.ac.uk/sper. 

Although this position is outside the nominal 90% BAT error circle, 
it is probably the GRB. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (8.65 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 2.7
(+2.23/-1.97) x 10^21 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 5.57e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 133 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
The 8'x8' region for the list of sources generated on-board covers 19% of the
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.10. 

Burst Advocate for this burst is V. D'Elia (delia AT asdc.asi.it). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)


GRB_name: GRB150915A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18316
SUBJECT: GRB 150915A: MASTER-NET optical observations 
DATE:    15/09/15 22:38:43 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres
The Instituto de Astrofisica de Canarias

V. Lipunov, E. Gorbovskoy,  N.Tyurina, V.Kornilov,
P.Balanutsa, A.Kuznetsov, D.Kuvshinov, E.Popova
Lomonosov Moscow State University, Sternberg Astronomical Institute

K.Ivanov, O.Gres, N.M.Budnev, S.Yazev,
Irkutsk State University

D.Buckley, S. Potter, A.Kniazev, M.Kotze
South African Astronomical Observatory

A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik
Kislovodsk Solar Station of the Pulkovo Observatory

V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov, A.Gabovich
Blagoveschensk Educational State University, Blagoveschensk

V.Krushinski, I.Zalozhnih
Ural Federal University, Kourovka

Hugo Levato and Carlos Saffe
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)

Claudio Mallamaci, Carlos Lopez and Federico Podest
Observatorio Astronomico Felix Aguilar (OAFA)

MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in IAC (Tenerife, Spain) was pointed to the  GRB150915A 22 sec 
after notice time and 95 sec after trigger time at 2015-09-15 21:20:03 UT 
in two polarizations. On our first single  (20s exposure) and coadd  (760s 
exposure)  sets we haven't found optical transient  within SWIFT error-box 
(Elia et al. GCN 18315).
The 5-sigma upper limit has been about 17.3 on single and 19.8 on coadd 
image.

MASTER II  robotic telescope located in SAAO (South Africa) was pointed to 
the  GRB150915A 25 sec after notice time and 100 sec after trigger time at 
2015-09-15 21:20:07 UT in two polarizations. On our first (20s exposure) 
set we haven't found optical transient  within SWIFT error-box .
The 5-sigma upper limit has been about 17.2 mag

The message may be cited.


GRB_name: GRB150915A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18317
SUBJECT: GRB 150915A: GROND detection of an optical counterpart candidate
DATE:    15/09/16 06:40:48 GMT
FROM:    Jochen Greiner at MPI  <jcg@mpe.mpg.de>

R. Yates, J. Bolmer and J. Greiner (all MPE Garching) report on behalf of
the GROND team:

We observed the field of GRB 150915A (D'Elia et al., GCN 18315) simultaneously
in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at 
the 2.2 m MPG telescope at ESO La Silla Observatory (Chile). Observations 
started at 23:28 UT on 2015-09-15, 2.2 hours after the GRB trigger.

Based on a 42 minutes exposure at a mid-time of 3.7 hours after the BAT 
trigger, at an average seeing of 1.6" and at an average airmass of 1.0, 
we detect an optical counterpart at the edge of the Swift-XRT error-circle at
  RA = 21 18 37.84
  Decl. = -34 54 48.3
(+/- 0.3")

at the following with magnitudes (AB system)

g' = 23.0 +/- 0.1 mag,
r' = 23.1 +/- 0.1 mag,
i' = 22.9 +/- 0.2 mag,
z' = 22.7 +/- 0.2 mag,
J  > 19.9 mag,
H  > 19.3 mag,
K  > 17.9 mag.

The given magnitudes are derived based on calibrating the images against
GROND zeropoints in the optical and 2MASS in the NIR, and are not corrected 
for the expected Galactic foreground extinction corresponding to a reddening 
of E_(B-V) = 0.10 mag in the direction of the burst (Schlegel et al. 1998).


GRB_name: GRB150915A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18318
SUBJECT: GRB 150915A: VLT/X-shooter redshift
DATE:    15/09/16 07:51:37 GMT
FROM:    Valerio D'Elia at ASDC  <delia@asdc.asi.it>

V. D'Elia (ASI/ASDC and INAF-OAR), T. Kruehler (MPE), D. Xu (NAOC/CAS), Pall Jakobsson (Univ. Iceland), N. R. Tanvir (U. Leicester), A. de Ugarte Postigo (IAA/CSIC), D. Malesani (DARK/NBI) and J. P. U. Fynbo (DARK/NBI), report on behalf of a larger collaboration:

We observed the optical counterpart of GRB 150915A (D'Elia et al., GCN 18315) with the ESO VLT equipped with the X-shooter spectrograph. Four spectra with individual exposure time of 1200 s were secured covering the wavelength range 3,000-21,000 AA. Spectroscopy began 3.3 hr after the BAT trigger. The afterglow is well detected in our acquisition image at the position of the optical counterpart (Yates et al., GCN 18317).

We detect a number of absorption features at a common redshift of z = 1.968, including Ly-a, C IV, Al II, Si II, Fe II, Mg II. We also detect fine-structure lines at the same redshift (e.g. FeII* 2396 / 2389, and Si II* 1533). Finally, we report strong emission lines of [O II], H-alpha and H-beta at a similar redshift, thus confirming z=1.968 as the GRB/host galaxy redshift.

We thank the kind assistence of the observing staff at Paranal, in particular Steve Ertel.


GRB_name: GRB150910A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18319
SUBJECT: GRB 150910A: TSHAO optical observations
DATE:    15/09/16 11:35:17 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

A. Volnova (IKI), I. Reva (Fesenkov Astrophysical Institute), A. Kusakin 
(Fesenkov Astrophysical Institute), E. Mazaeva (IKI),  A. Pozanenko 
(IKI) report on behalf of larger GRB follow-up collaboration:

We observed the field of GRB 150910A (Pagani et al., GCN  18264)  with 
Zeiss-1000 (East) 1-m telescope of Tien Shan Astronomical Observatory on 
Sep. 11 and Sep. 12.  We obtained several images in R filter.  The 
afterglow  (Pagani et al., GCN 18264; Zheng & Filippenko, GCN 18265) is 
clearly visible in a combined image on Sep. 11 and on Sep. 12 we 
obtained upper limit.  The photometry of the combined images are following

Date       UT start    t-T0     Filter  Exp.     OT       Err
                        (mid, days)      (s)

2015-09-11 18:39:41    1.38753  R       16*300   21.87    0.10
2015-09-12 19:03:44    2.39553  R       21*300   >22.3   (3 sigma)

The photometry is based on SDSS stars used in GCN 18281 (Mazaeva et al.)


GRB_name: GRB150910A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18320
SUBJECT: GRB 150910A: Mt. Terskol observatory optical observations
DATE:    15/09/16 11:45:10 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

A. Volnova (IKI), A. Sergeev (Terskol Branch of INASAN), M. Andreev 
(Terskol Branch of INASAN),  E. Mazaeva (IKI), A. Pozanenko (IKI) report 
on behalf of larger GRB follow-up collaboration:

We observed the field of GRB 150910A (Pagani et al., GCN 18264) with 
Zeiss-2000 telescope of Mt. Terskol observatory in R-filter starting on 
Sep. 11 (UT) 00:40:58.  The afterglow (Pagani et al., GCN 18264; Zheng & 
Filippenko, GCN 18265) is clearly detected in a each image. The 
photometry of a combined image is following

Date UT start       t-T0    Filter Exp.   OT     Err
                     (mid, days)    (s)

2015-09-11 00:40:58 0.67083 R      13*120 20.90  0.07

The photometry is based on SDSS stars used in GCN 18281 (Mazaeva et al.)


GRB_name: GRB150906B
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18321
SUBJECT: GRB 150906B: Further analysis of the Konus-Wind data
DATE:    15/09/16 13:33:08 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

D. Svinkin, D. Frederiks, and V. Pal'shin,
on behalf of the Konus-Wind team, report:

It was suggested by Levan et. al. (GCN 18263) that the short-duration,
hard-spectrum, bright GRB 150906B (Golenetskii et al. GCN 18259) might
be connected with the NGC 3313 galaxy group. Continuing the discussion
on the possible origin of GRB 150906B (Ruffini et al. GCN 18296 and
F. Zhang et al. GCN 18298) we present a further analysis of the KW data
for this GRB.

Among ~300 bursts from the Konus catalog of short GRBs
(Svinkin et al., in preparation), GRB 150906B is within top 25%
in the terms of 16-ms peak energy flux and within top 3% in the terms
of the total energy fluence, both in the 20 keV - 10 MeV range.
In the terms of Epeak (CPL model), the burst is within 25% hardest
GRBs in the sample.

However, the burst duration is rather long T50=0.952+/-0.036 s
(T90 = 1.642+/-0.076 s). The position of the GRB 150906B in
the hardness-duration diagram (logT50-logHR32) of 1143 KW bright GRBs
cannot exclude that the burst comes from the long GRB population.
The figure showing the hardness-duration diagram is available at
http://www.ioffe.ru/LEA/GRBs/GRB150906_T31340/GRB150906B_T50HR.png
The contours denote the 1, 2, and 3 sigma confidence regions for
two-dimensional Gaussian distributions. The HR32 is the ratio of counts
in the 200-760 keV and 50-200 keV bands accumulated during burst
duration. The vertical dashed line at T50=0.6 s marks the boundary used
by Svinkin et al. to distinguish between short and long KW GRBs.

The spectral lag calculated between the KW 400-1500 keV and 25-100 keV
band light curves (tau = 70+/-40 ms, 68% confidence level)
is consistent, within 68% CL, with the KW lag distributions
for both short and long GRBs.

Thus, being hard enough, GRB 150906B cannot be unambiguously
classified as a short/hard from the KW data.


GRB_name: GRB150915A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18322
SUBJECT: GRB 150915A: Swift UVOT upper limits
DATE:    15/09/16 17:53:39 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>

A. A. Breeveld (UCL-MSSL) and V. D'Elia (ASDC) report on behalf of the
Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150915A
295s after the BAT trigger (D'Elia et al., GCN Circ. 18315).
No optical afterglow consistent with the XRT position (Dâ€™Elia et al.,
GGN Circ. 18315) or the GROND position (Yates et al., GCN Circ. 18317)
is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding
chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

u_FC               295          545          246         >20.0
white              576          769           39         >19.9
v                  625          818           39         >18.2
b                  550          745           39         >19.2
u                  295         4267          434         >20.0

The magnitudes in the table are not corrected for the Galactic
extinction due to the reddening of E(B-V) = 0.10 in the direction of the
burst (Schlegel et al. 1998).


GRB_name: GRB150915A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18323
SUBJECT: GRB 150915A: NOT observations of a brightening afterglow
DATE:    15/09/16 23:25:46 GMT
FROM:    Dong Xu at NAOC/CAS  <dong.dark@gmail.com>

D. Xu (NAOC/CAS), A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), N. R.
Tanvir (Univ. Leicester), D. Malesani (DARK/NBI), T. Kruehler (MPE),
P. Jakobsson (Univ. Iceland), S. Schulze (PUC, MAS), V. D'Elia
(ASI/ASDC and INAF-OAR), K. Karhunen (Turku Univ.), report on behalf
of a larger collaboration:

We observed the field of GRB 150915A (D'Elia et al., GCN 18315) with
the Nordic Optical Telescope equipped with the ALFOSC camera. Two
observations composed each by 3x300 s exposures in R-band were taken
with the mean times of 0.80 and 3.05 hr after the GRB trigger.

The source detected by GROND and reported by Yates et al. (GCN 18317)
is clearly visible in our images at both epochs, with a magnitude of
R(Vega) = 22.52 +- 0.09 on our first epoch (assuming R = 16.72 for the
star at RA = 21:18:34.76, Dec = -34:53:44.9).

Interestingly, the object is found to brighten between the two epochs
by 0.28 +- 0.11 mag - a behavior not common, though not unprecedented.


GRB_name: GRB150915A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18325
SUBJECT: GRB150915A : IRSF NIR upper limits
DATE:    15/09/17 01:58:08 GMT
FROM:    Daisuke Kuroda at OAO/NAOJ  <dikuroda@oao.nao.ac.jp>

K. L. Murata (Nagoya U.), S. Nagatomo (Kyoto U.), and T. Nagayama (Kagoshima U.)

We observed the field of GRB150915A (D'Elia et al., GCN Circular #18315) with the near-infrared (J, H, Ks) simultaneous
imaging camera SIRIUS attached to 1.4 m telescope IRSF ( InfraRed Survey Facility) in Sutherland observatory, South Africa.

The observations started on 2015-09-15 23:45:25 UT (~ 2.5 hours after the burst).
We could not detect the afterglow within the XRT error circle reported in the GCN circular in the three bands.
We have obtained the following preliminary upper limits (Vega magnitude system):

J  > 16.47
H  > 15.91
Ks > 15.64.

Given magnitudes were calibrated against 2MASS point sources in this field.
The upper limits were determined as the magnitudes of the faintest star within 1 arcmin from the XRT position.

This observation was carried out by IRSF and OISTER collaboration.


GRB_name: GRB150911A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18326
SUBJECT: Konus-Wind observation of  GRB 150911A
DATE:    15/09/17 04:21:46 GMT
FROM:    Anastasia Tsvetkova at Ioffe Institute  <tsvetkova@mail.ioffe.ru>

S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lysenko, A. Kozlova and T. Cline
on behalf of the Konus-Wind team, report:

The long-duration GRB 150911A (Swift-BAT trigger #655262:
Starling, et al., GCN Circ. 18280; Markwardt , et al., GCN Circ. 18292)
was detected by Konus-Wind in the waiting mode.

The burst light curve shows a single pulse with a total duration of ~9 s.

As observed by Konus-Wind, the burst had a fluence of
3.13(-0.20,+0.26)x10^-6 erg/cm2 and a 2.944-s peak flux,
measured from ~T0(BAT)+2.5 s, of 4.01(-0.32,+0.59)x10^-7 erg/cm2/s
(both in the 20 - 1000 keV energy range).

Fitting the K-W 3-channel time-integrated spectrum
(measured from ~T0(BAT)-0.5 s to ~T0(BAT)+8.5 s)
by a simple power-law model yields the photon index
-2.32(-0.09,+0.09), chi2=0.6/1 dof.

All the quoted errors are estimated at the 1 sigma confidence level.
All the presented results are preliminary.

The K-W light curve of this burst is available at
http://www.ioffe.rssi.ru/LEA/GRBs/GRB150911A/

[GCN OPS NOTE(16sep15):  This circular was delayed  ~12 hours
in distribution because of an operation mistake at GCN.]


GRB_name: GRB150910A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18327
SUBJECT: GRB 150910A: AAO optical observations
DATE:    15/09/17 07:27:12 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

E. Mazaeva (IKI), R. Inasaridze (AAO), O. Kvaratskhelia(AAO), I. Molotov 
(KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up 
collaboration:

We observed the field of GRB 150910A (Pagani et al., GCN  18264)  with 
AS-32 (0.7m) telescope of Abastumani Observatory starting on Sep. 11 
(UT) 20:32:45. We obtained several unfiltered images. The afterglow 
(Pagani et al., GCN 18264; Zheng & Filippenko, GCN 18265) is clearly 
visible in a combined image. The photometry of the combined image is 
following

Date       UT start    t-T0     Filter  Exp.     OT       Err
                        (mid, days)      (s)

2015-09-11 20:32:45    1.46327  none    49*120   21.55 +/- 0.08

The photometry is based on SDSS stars used in GCN 18281 (Mazaeva et 
al.), R magnitude deduced from Lupton's transformations.


GRB_name: GRB150915A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18328
SUBJECT: GRB 150915A, Swift-BAT refined analysis
DATE:    15/09/17 09:05:19 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

D. M. Palmer (LANL), S. D. Barthelmy (GSFC),  J. R. Cummings (GSFC/UMBC),
V. D'Elia (ASDC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), T. Sakamoto (AGU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 150915A (trigger #655721)
(D'Elia, et al., GCN Circ. 18315).  The BAT ground-calculated position is
RA, Dec = 319.675, -34.874 deg which is
  RA(J2000)  =  21h 18m 42.0s
  Dec(J2000) = -34d -52' -27.1"
with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 55%.

The mask-weighted light curve shows a weak complex structure that starts
at ~ T0-70 s and ends at ~T0+120 s. There might be additional weak emission
that starts since the beginning of the event data. T90 (15-350 keV)
is 164.7 +- 49.7 sec (estimated error including systematics).

The time-averaged spectrum from T-69.0 to T+116.8 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.51 +- 0.42.  The fluence in the 15-150 keV band is 8.0 +- 1.8 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+17.68 sec in the 15-150 keV band
is 0.5 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/655721/BA/


GRB_name: GRB150915A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18329
SUBJECT: GRB 150915A: Swift-XRT refined Analysis
DATE:    15/09/17 13:20:26 GMT
FROM:    Valerio D'Elia at ASDC  <delia@asdc.asi.it>

A. D'ai (INAF-IASFPA), A. Maselli  (INAF-IASFPA), A. Melandri
(INAF-OAB), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), D.N.
Burrows (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), 
L. Izzo (URoma/ICRA) and V. D'Elia (ASDC) report on behalf of the
Swift-XRT team:

We have analysed 12 ks of XRT data for the Swift/BAT-detected burst GRB
150915A (D'Elia et al. GCN Circ. 18315), from 118 s to 126.0 ks after
the  Swift/BAT trigger. The data comprise 256 s in Windowed Timing (WT)
mode (the first 8 s were taken while Swift was slewing) with the
remainder in Photon Counting (PC) mode. The refined XRT position is RA,
Dec = 319.6584, -34.9136 which is equivalent to:

RA (J2000): 21 18 38.01
Dec(J2000): -34 54 49.1

with an uncertainty of 3.7 arcsec (radius, 90% confidence). This
position is 5.1 arcmin from the Swift/BAT position. 

The light curve can be modelled with an initial power-law decay with an
index of alpha=0.5 (+/-0.3), followed by a break at T+170 s to an alpha
of 3.94 (+0.15, -0.13).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.79 (+/-0.04). The
best-fitting absorption column is  7.8 (+1.7, -1.6) x 10^21 cm^-2, at a
redshift of 1.968, in addition to the Galactic value of 8.6 x 10^20
cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed)
0.3-10 keV flux conversion factor deduced from this spectrum  is 3.7 x
10^-11 (4.5 x 10^-11) erg cm^-2 count^-1. 

A summary of the WT-mode spectrum is thus:
Galactic foreground: 8.6 x 10^20 cm^-2
Intrinsic column:    7.8 (+1.7, -1.6) x 10^21 cm^-2 at z=1.968
Photon index:      1.79 (+/-0.04)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00655721.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB150919A
Detection_method: IPN Triangulation
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18355
SUBJECT: IPN Triangulation of GRB 150919A (short / hard)
DATE:    15/09/22 20:40:06 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

K. Hurley, on behalf of the IPN,

I. G. Mitrofanov, D. Golovin, M. L. Litvak, and A. B. Sanin,
on behalf of the HEND-Odyssey GRB team,

S. Golenetskii, R. Aptekar, V. Pal'shin, D. Frederiks,
D. Svinkin, and T. Cline on behalf of the Konus-Wind team,

A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
and

W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr,
on behalf of the GRS-Odyssey GRB team, report:

A short-duration GRB 150919A has been detected by Konus-Wind,
INTEGRAL (SPI-ACS), and Mars-Odyssey (HEND), so far,
at about 74595 s UT (20:43:15).

We have triangulated it to a preliminary, 3 sigma error box whose 
coordinates are:
---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   132.960 (08h 51m 50s) +44.066 (+44d 03' 59")
  Corners:
   132.432 (08h 49m 44s) +43.742 (+43d 44' 33")
   132.726 (08h 50m 54s) +44.076 (+44d 04' 34")
   133.487 (08h 53m 57s) +44.379 (+44d 22' 43")
   133.193 (08h 52m 46s) +44.055 (+44d 03' 20")
  ---------------------------------------------
The error box area is 412 sq. arcmin, and its maximum
dimension is 59 arcmin (the minimum one is 11 arcmin).
The Sun distance was 58 deg.

This box may be improved.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB150919_T74595/IPN/

The Konus-Wind time history and spectrum will be given in a forthcoming 
GCN Circular.


GRB_name: GRB150919A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18356
SUBJECT: Konus-Wind observation of GRB 150919A
DATE:    15/09/22 20:58:31 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

S. Golenetskii, R. Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, A. Kozlova,
and T. Cline on behalf of the Konus-Wind team, report:

The short-duration GRB 150919A
(IPN triangulation: Hurley et al., GCN Circ. 18355)
triggered Konus-Wind at T0=74595.399 s UT (20:43:15.399).

The burst light curve shows a single pulse with a duration of ~0.2 s
followed by a weak emission up to ~1.2 s.
The emission is seen up to ~2 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB150919_T74595/

As observed by Konus-Wind, the burst
had a fluence of 1.46(-0.27,+0.33)x10^-6 erg/cm2,
and a 16-ms peak flux, measured from T0 s,
of 1.43(-0.44,+0.50)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+0.128 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.61(-0.34,+0.43)
and Ep = 405(-114,+199) keV (chi2 = 22/25 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta <-1.8
(chi2 = 21/24 dof)

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.


GRB_name: GRB150922A
Detection_method: IPN Triangulation
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18357
SUBJECT: IPN Triangulation of GRB 150922A (short/hard)
DATE:    15/09/22 21:10:23 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

S. Golenetskii, R. Aptekar, V. Pal'shin, D. Frederiks,
D. Svinkin, and T. Cline on behalf of the Konus-Wind team,

K. Hurley, on behalf of the IPN,

I. G. Mitrofanov, D. Golovin, M. L. Litvak, and A. B. Sanin,
on behalf of the HEND-Odyssey GRB team,

V. Connaughton, M. S. Briggs, C. Meegan, V. Pelassa,
and A. Goldstein, on behalf of the Fermi GBM team,

A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
and

W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr,
on behalf of the GRS-Odyssey GRB team, report:

The short-duration, hard-spectrum GRB 150922A has been detected by 
Konus-Wind, Fermi (GBM trigger 464593053/150922234), Mars-Odyssey 
(HEND), and INTEGRAL (SPI-ACS), so far, at about 20249 s UT (05:37:29).

We have triangulated it to a preliminary, 3 sigma error box whose 
coordinates are:
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   294.381 (19h 37m 31s)  -5.486 ( -5d 29' 10")
  Corners:
   294.315 (19h 37m 16s)  -6.116 ( -6d 06' 57")
   294.303 (19h 37m 13s)  -5.399 ( -5d 23' 56")
   294.448 (19h 37m 48s)  -4.881 ( -4d 52' 51")
   294.458 (19h 37m 50s)  -5.573 ( -5d 34' 25")
  ---------------------------------------------
The error box area is 385 sq. arcmin, and its maximum
dimension is 75 arcmin (the minimum one is 9.1 arcmin).
The Sun distance was 115 deg.

This box may be improved.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB150922_T20250/IPN/

The time history and spectrum will be given in forthcoming GCN Circulars.


GRB_name: GRB150922A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18358
SUBJECT: GRB 150922A: Fermi GBM observation
DATE:    15/09/23 09:04:05 GMT
FROM:    Oliver Roberts at UCD/Fermi  <oliver.roberts@ucd.ie>

O.J. Roberts (UCD), A. von Kienlin (MPE) and
C. Meegan (UAH),report on behalf of the Fermi GBM Team:

"At 05:37:29.08 UT on 22 September 2015, the Fermi
Gamma-Ray Burst Monitor triggered and located
GRB 150922A (trigger 464593053 / 150922234), which was
also detected by IPN (Svinkin et al. 2015, GCN 18357).
The GBM on-ground location is consistent with the IPN
position. The angle from the Fermi LAT boresight is
about 38 degrees.

The GBM light curve shows a short burst with a
duration (T90) of 0.144 s (50-300 keV). The time-averaged
spectrum from T0-0.016 to T0+0.128 s is best fit by a
power law function with an exponential high-energy cutoff.
The power law index is -0.55 +/- 0.11 and the cutoff energy,
parameterized as Epeak, is 625 +/- 97  keV.

The event fluence (10-1000 keV) in this time interval
is (8.0 +/- 0.4) E-07 erg/cm^2. The 64 ms peak photon
flux measured starting from T0-0.016 s in the 10-1000 keV
band is 23.0 +/- 1.3 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."


GRB_name: GRB150922A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18360
SUBJECT: Konus-Wind observation of GRB 150922A
DATE:    15/09/23 13:09:30 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

S. Golenetskii, R. Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, A. Kozlova,
and T. Cline on behalf of the Konus-Wind team, report:

The short-duration, hard-spectrum GRB 150922A
(IPN triangulation: Golenetskii et al., GCN 18357;
Fermi GBM detection: Roberts et al., GCN 18358)
triggered Konus-Wind at T0=20250.916 s UT (05:37:30.916).

The burst light curve shows a multipeak structure
with a total duration of ~0.16 s.
The emission is seen up to ~2 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB150922_T20250/

As observed by Konus-Wind, the burst
had a fluence of 7.94(-1.93,+2.25)x10^-7 erg/cm2,
and a 16-ms peak flux, measured from T0-0.008 s,
of 1.34(-0.52,+0.59)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+0.064 s)
is best fit in the 20 keV - 2 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.17(-0.66,+1.10)
and Ep = 393(-132,+222) keV (chi2 = 11/13 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2
(chi2 = 11/12 dof)

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.


GRB_name: GRB150925A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18365
SUBJECT: GRB 150925A: Swift detection of a burst
DATE:    15/09/25 04:27:53 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

J. L. Racusin (NASA/GSFC), A. D'Ai (INAF-IASFPA),
A. Maselli (INAF-IASFPA), D. M. Palmer (LANL) and M. H. Siegel (PSU)
report on behalf of the Swift Team:

At 04:09:28 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150925A (trigger=656604).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 227.520, -19.628 which is 
   RA(J2000) = 15h 10m 05s
   Dec(J2000) = -19d 37' 41"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  Only partial BAT lightcurve data is 
currently available, and so no description of this image trigger
can be given. 

The XRT began observing the field at 04:11:48.9 UT, 140.1 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source with an enhanced position: RA, Dec
227.5340, -19.6325 which is equivalent to:
   RA(J2000)  = 15h 10m 08.16s
   Dec(J2000) = -19d 37' 57.1"
with an uncertainty of 2.1 arcseconds (radius, 90% containment). This
location is 50 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (1.01 x
10^21 cm^-2, Willingale et al. 2013), with an excess column of 4.7
(+4.53/-2.33) x 10^21 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 3.82e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 148 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
The 8'x8' region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.10. 

Burst Advocate for this burst is J. L. Racusin (judith.racusin AT nasa.gov). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)


GRB_name: GRB150925A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18366
SUBJECT: GRB 150925A: Enhanced Swift-XRT position
DATE:    15/09/25 12:48:22 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 1379 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 150925A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 227.53421, -19.63298 which is equivalent
to:

RA (J2000): 15h 10m 8.21s
Dec (J2000): -19d 37' 58.7"

with an uncertainty of 1.5 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.


GRB_name: GRB150925A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18367
SUBJECT: GRB 150925A: Swift-XRT refined Analysis
DATE:    15/09/25 16:27:03 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

A. Maselli  (INAF-IASFPA), A. Melandri (INAF-OAB), B. Sbarufatti
(INAF-OAB/PSU), D.N. Burrows (PSU), T.G.R. Roegiers (PSU), J.P. Osborne
(U. Leicester), K.L. Page (U. Leicester), C. Pagani (U. Leicester), P.
D'Avanzo (INAF-OAB) and J.L. Racusin report on behalf of the Swift-XRT
team:

We have analysed 9.0 ks of XRT data for GRB 150925A (Racusin et al. GCN
Circ. 18365), from 129 s to 22.8 ks after the  BAT trigger. The data
comprise 175 s in Windowed Timing (WT) mode (the first 9 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Osborne et
al. (GCN Circ. 18366).

The light curve can be modelled with an initial power-law decay with an
index of alpha=3.30 (+/-0.09), followed by a break at T+877 s to an
alpha of 1.20 (+0.19, -0.22).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.62 (+/-0.09). The
best-fitting absorption column is  2.7 (+/-0.5) x 10^21 cm^-2, in
excess of the Galactic value of 1.0 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.89 (+0.25, -0.23)
and a best-fitting absorption column of 3.4 (+1.2, -1.0) x 10^21 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 4.1 x 10^-11 (5.8 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      3.4 (+1.2, -1.0) x 10^21 cm^-2
Galactic foreground: 1.0 x 10^21 cm^-2
Excess significance: 3.8 sigma
Photon index:      1.89 (+0.25, -0.23)

If the light curve continues to decay with a power-law decay index of
1.20, the count rate at T+24 hours will be 6.3 x 10^-4 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.6 x
10^-14 (3.7 x 10^-14) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00656604.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB150925A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18368
SUBJECT: GRB 150925A: Swift-BAT refined analysis
DATE:    15/09/25 16:46:23 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>

T. Sakamoto (AGU), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL), J. L. Racusin (NASA/GSFC),
M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
 
Using the data set from T-239 to T+963 sec from the recent telemetry downlinks,
we report further analysis of BAT GRB 150925A (trigger #656604)
(Racusin, et al., GCN Circ. 18365).  The BAT ground-calculated position is
RA, Dec = 227.538, -19.640 deg, which is 
   RA(J2000)  =  15h 10m 09.0s 
   Dec(J2000) = -19d 38' 22.3" 
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 56%.
 
The mask-weighted light curve show several overlapping peaks starting at ~T-0,
peaking at ~T+25 sec, and ending at ~T+180 sec.  T90 (15-350 keV) is
121 +- 27 sec (estimated error including systematics).
 
The time-averaged spectrum from T+3.51 to T+149.61 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.19 +- 0.20.  The fluence in the 15-150 keV band is 1.4 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+30.68 sec in the 15-150 keV band
is 0.6 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level. 
 
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/656604/BA/


GRB_name: GRB150925A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18369
SUBJECT: GRB 150925A: Swift/UVOT Upper Limits
DATE:    15/09/26 03:01:53 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <siegel@swift.psu.edu>

M. H. Siegel (PSU) and J. L. Racusin (NASA/GSFC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150925A
149 s after the BAT trigger (Racusin et al., GCN Circ. 18365).
No optical afterglow consistent with the XRT position
(Osborne et al. GCN Circ. 18366)
is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC           149          298          147         >20.2
u_FC               307          557          246         >19.7
white              149        13178         1385         >21.2
v                  637         7068          510         >19.7
b                  563        18924         1676         >20.7
u                  307        18430         2310         >20.2
w1                 688        17516         1333         >20.8
m2                1589        22808          586         >21.1
w2                1019         6864          452         >19.8

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.10 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB151001A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18373
SUBJECT: GRB 151001A: Swift detection of a burst with an optical counterpart
DATE:    15/10/01 16:38:56 GMT
FROM:    Jamie A. Kennea at PSU/Swift-XRT  <kennea@swift.psu.edu>

M. Stamatikos (OSU/NASA/GSFC), S. D. Barthelmy (GSFC),
P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC),
S. L. Gibson (U Leicester), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA), N. P. M. Kuin (UCL-MSSL),
A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC),
C. Pagani (U Leicester), B. Sbarufatti (INAF-OAB/PSU) and
M. H. Siegel (PSU) report on behalf of the Swift Team:

At 15:04:22 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 151001A (trigger=657286).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 233.731, +10.971 which is 
   RA(J2000) = 15h 34m 55s
   Dec(J2000) = +10d 58' 16"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a couple overlapping peaks
with a duration of about 100 sec.  The peak count rate
was ~1000 counts/sec (15-350 keV), at ~10 sec after the trigger. 

The XRT began observing the field at 15:05:26.9 UT, 64.0 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 233.7289, 10.9669 which
is equivalent to:
   RA(J2000)  = 15h 34m 54.94s
   Dec(J2000) = +10d 58' 00.8"
with an uncertainty of 2.0 arcseconds (radius, 90% containment). This
location is 16 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (3.53 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 1.3
(+1.39/-1.27) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 67 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  = 15:34:54.90 = 233.72874
  DEC(J2000) = +10:58:02.1  =  10.96724
with a 90%-confidence error radius of about 0.62 arc sec. This position is 3.8
arc sec. from the center of the XRT error circle. The estimated magnitude is
17.94 with a 1-sigma error of about  0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.04. 

Burst Advocate for this burst is M. Stamatikos (Michael.Stamatikos-1 AT nasa.gov). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)


GRB_name: GRB151001B
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18374
SUBJECT: GRB 151001B: Swift detection of a burst
DATE:    15/10/01 18:44:33 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

H. A. Krimm (CRESST/GSFC/USRA), S. D. Barthelmy (GSFC),
A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC),
C. Pagani (U Leicester), B. Sbarufatti (INAF-OAB/PSU) and
M. H. Siegel (PSU) report on behalf of the Swift Team:

At 18:29:36 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 151001B (trigger=657321).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 336.845, +64.661, which is 
   RA(J2000)  =  22h 27m 23s
   Dec(J2000) = +64d 39' 39"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is typical for image triggers, there is nothing
significant in the real-time TDRSS light curve. 

The XRT began observing the field at 18:31:55.6 UT, 138.9 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source with an enhanced position: RA, Dec
336.8384, 64.6937 which is equivalent to:
   RA(J2000)  = 22h 27m 21.22s
   Dec(J2000) = +64d 41' 37.4"
with an uncertainty of 2.4 arcseconds (radius, 90% containment). This
location is 118 arcseconds from the BAT onboard position, within the
BAT error circle. This position may be improved as more data are
received; the latest position is available at
http://www.swift.ac.uk/sper. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (6.51 x
10^21 cm^-2, Willingale et al. 2013), with an excess column of 6.8
(+6.23/-4.70) x 10^21 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 1.89e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 148 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
The 8'x8' region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
1.71. 

Burst Advocate for this burst is H. A. Krimm (hans.krimm AT nasa.gov). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)


GRB_name: GRB151001A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18375
SUBJECT: GRB 151001A: Fermi GBM detection
DATE:    15/10/02 01:01:32 GMT
FROM:    Bagrat Mailyan at UAH  <bm0054@uah.edu>

B. Mailyan (UAH), P. Veres (UAH) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 15:04:22.41  UT on 01 October 2015, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 151001A (trigger 465404666 / 151001628)
which was also detected by the Swift/BAT and XRT
(M. Stamatikos et al. 2015, GCN 18373)
The GBM on-ground location is consistent with the Swift position.


The angle from the Fermi LAT boresight at the GBM trigger time is 22 degrees.


The GBM light curve has a duration (T90) of about 15.1 s (50-300 keV).
The time-averaged spectrum from T0-6.1 s to T0+4.1 s is
adequately fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.54 +/- 0.21 and
the cutoff energy, parameterized as Epeak, is 213.80 +/- 36.90 keV.


The event fluence (10-1000 keV) in this time interval is
(1.798 +/- 0.195)E-06  erg/cm^2. The 1-sec peak photon flux measured
starting from T0+2.75 s in the 10-1000 keV band
is 2.2 +/- 0.2 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."


GRB_name: GRB151001A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18376
SUBJECT: GRB 151001A: Enhanced Swift-XRT position
DATE:    15/10/02 02:33:32 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 2627 s of XRT Photon Counting mode data and 5 UVOT
images for GRB 151001A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 233.72875, +10.96720 which is equivalent
to:

RA (J2000): 15h 34m 54.90s
Dec (J2000): +10d 58' 01.9"

with an uncertainty of 1.5 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.


GRB_name: GRB151001B
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18377
SUBJECT: GRB 151001B: Enhanced Swift-XRT position
DATE:    15/10/02 04:03:19 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 1574 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 151001B, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 336.83909, +64.69375 which is equivalent
to:

RA (J2000): 22h 27m 21.38s
Dec (J2000): +64d 41' 37.5"

with an uncertainty of 1.6 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.


GRB_name: GRB151001A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18378
SUBJECT: GRB 151001A: Swift-XRT refined Analysis
DATE:    15/10/02 06:19:04 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

A. Melandri (INAF-OAB), D.N. Burrows (PSU), T.G.R. Roegiers (PSU), L.M.
McCauley (PSU), K.L. Page (U. Leicester), C. Pagani (U. Leicester),
A.P. Beardmore (U. Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC)
and M. Stamatikos report on behalf of the Swift-XRT team:

We have analysed 8.2 ks of XRT data for GRB 151001A (Stamatikos et al.
GCN Circ. 18373), from 49 s to 36.0 ks after the  BAT trigger. The data
comprise 9 s in Windowed Timing (WT) mode (taken while Swift was
slewing), with the remainder in Photon Counting (PC) mode. The enhanced
XRT position for this burst was given by Beardmore et al. (GCN Circ.
18376).

The late-time light curve (from T0+4.8 ks) can be modelled with a
power-law decay with a decay index of alpha=1.18 (+0.23, -0.20).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.78 (+/-0.14). The
best-fitting absorption column is  8.0 (+4.0, -3.6) x 10^20 cm^-2, in
excess of the Galactic value of 3.5 x 10^20 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 3.7 x 10^-11 (4.2 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      8.0 (+4.0, -3.6) x 10^20 cm^-2
Galactic foreground: 3.5 x 10^20 cm^-2
Excess significance: 2.1 sigma
Photon index:      1.78 (+/-0.14)

If the light curve continues to decay with a power-law decay index of
1.18, the count rate at T+24 hours will be 2.8 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.0 x
10^-13 (1.2 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00657286.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB151001A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18379
SUBJECT: GRB 151001A: NOT imaging
DATE:    15/10/02 09:07:50 GMT
FROM:    Thomas Kruehler at MPE Garching  <kruehler@mpe.mpg.de>

T. Kruehler (MPE), J. P. U. Fynbo, D. Malesani (DARK/NBI), and P. 
Jakobsson (U. Iceland) report on behalf of a larger collaboration:

We observed the field of GRB 151001A (Swift trigger 657286, Stamatikos 
et al., GCN Circ. 18373) with the 2.5-m Nordic Optical Telescope (NOT) 
equipped with ALFOSC on the evening of 01-Oct-2015 between 19:55-20:24 
UT (5 hr after the burst). In SDSS filters r and g we clearly detect the 
optical afterglow of GRB 151001A at the position given by UVOT 
(Stamatikos et al., GCN Circ. 18373). We derive AB magnitudes of

g = 22.18 +/- 0.05
r = 21.51 +/- 0.08

calibrated against SDSS field stars. The g-r color of the afterglow is 
relatively red compared to typical afterglows.


GRB_name: GRB151001B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18380
SUBJECT: GRB 151001B: MASTER-NET early optical observations. 
DATE:    15/10/02 09:22:48 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov
Blagoveschensk Educational State University, Blagoveschensk

E. Gorbovskoy, V. Lipunov, M.Pruzhinskaya, V.Kornilov, D.Kuvshinov, 
N.Tyurina, N.Shatskiy, P.Balanutsa, D.Zimnukhov, A.Kuznetsov, V.V.Chazov, 
D.Denisenko,  A.Sankovich
Lomonosov Moscow State University,
Sternberg Astronomical Institute, Moscow State University

K.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk
Irkutsk State University

V.Krushinski, I.Zalozhnih,  A. Popov
Ural Federal University, Kourovka

A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik
Kislovodsk Solar Station of the Pulkovo Observatory

D.Buckley, S. Potter, A.Kniazev, M.Kotze
South African Astronomical Observatory

Hugo Levato and Carlos Saffe
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)

Claudio Mallamaci, Carlos Lopez and Federico Podest
Observatorio Astronomico Felix Aguilar (OAFA)

R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres
The Instituto de Astrofisica de Canarias


MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in Blagoveschensk was pointed to the  GRB151001B   20 sec after 
notice time and 96 sec after trigger time at 2015-10-01 18:31:13 UT. On 
our first (20s exposure)  set we haven't found optical transient  within 
SWIFT error-box (Krimm et. al GCN 18374).
The 5-sigma upper limit has been about 18.0 mag
The message may be cited.


GRB_name: GRB151001A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18381
SUBJECT: GRB 151001A: Swift/UVOT Detection
DATE:    15/10/02 12:44:45 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld@ucl.ac.uk>

A. A. Breeveld (UCL-MSSL) and M. Stamatikos (OSU/NASA/GSFC) report on 
behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 151001A 46 
s after the BAT trigger (Stamatikos et al., GCN Circ. 18373).
A fading source consistent with the enhanced XRT position (Beardmore et 
al. GCN Circ. 18376) is detected in the initial UVOT exposures.

The preliminary UVOT position is:
     RA  (J2000) =  15:34:54.90 = 233.72875 (deg.)
     Dec (J2000) = +10:58:02.2  =  10.96728 (deg.)
with an estimated uncertainty of 0.43 arc sec. (radius, 90% confidence).

Preliminary detections and 3-sigma upper limits using the UVOT 
photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for 
the early exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white               67          217          147         17.82 Â± 0.06
white              559          578           20         19.5  Â± 0.3
v                   46         1403          110         18.78 Â± 0.29
b                  534         1502           97         19.60 Â± 0.29
u                  279          529          246         19.13 Â± 0.15
w1                 657         1453           97        >19.3
m2                 806         1428           39        >18.0
w2                1358         1552           39        >18.4

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.04 in the direction of the 
burst (Schlegel et al. 1998).


GRB_name: GRB151001B
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18382
SUBJECT: GRB 151001B: Swift-BAT refined analysis
DATE:    15/10/02 13:09:51 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>

T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU),
(i.e. the Swift-BAT team):
 
Using the data set from T-239 to T+963 sec from the recent telemetry downlinks,
we report further analysis of BAT GRB 151001B (trigger #657321)
(Krimm, et al., GCN Circ. 18374).  The BAT ground-calculated position is
RA, Dec = 336.974, 64.637 deg, which is 
   RA(J2000)  =  22h 27m 53.7s 
   Dec(J2000) = +64d 38' 13.5" 
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 28%.
 
The mask-weighted light curves shows several overlapping peaks starting
at ~T-40 sec, peaking at ~T+50 sec, and ending at ~T+150 sec.
T90 (15-350 keV) is 109 +- 17 sec (estimated error including systematics).
 
The time-averaged spectrum from T-23.3 to T+97 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.12 +- 0.27.  The fluence in the 15-150 keV band is 1.4 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+47.47 sec in the 15-150 keV band
is 0.5 +- 0.3 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level. 
 
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/657321/BA/


GRB_name: GRB151001B
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18383
SUBJECT: GRB 151001B: Swift-XRT refined Analysis
DATE:    15/10/02 13:44:02 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

T.G.R. Roegiers (PSU), L.M. McCauley (PSU), J.A. Kennea (PSU), C.
Pagani (U. Leicester), A.P. Beardmore (U. Leicester), P.A. Evans (U.
Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), A. D'ai
(INAF-IASFPA) and H.A. Krimm report on behalf of the Swift-XRT team:

We have analysed 6.4 ks of XRT data for GRB 151001B (Krimm et al. GCN
Circ. 18374), from 129 s to 59.3 ks after the  BAT trigger. The data
comprise 132 s in Windowed Timing (WT) mode (the first 8 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Evans et
al. (GCN Circ. 18377).

The light curve can be modelled with an initial power-law decay with an
index of alpha=2.38 (+/-0.08), followed by a break at T+963 s to an
alpha of 1.12 (+0.12, -0.13).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.78 (+0.17, -0.16). The
best-fitting absorption column is  1.09 (+0.19, -0.18) x 10^22 cm^-2,
in excess of the Galactic value of 6.5 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 2.20 (+0.31, -0.30)
and a best-fitting absorption column of 1.9 (+0.5, -0.4) x 10^22 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 5.4 x 10^-11 (1.4 x 10^-10) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      1.9 (+0.5, -0.4) x 10^22 cm^-2
Galactic foreground: 6.5 x 10^21 cm^-2
Excess significance: 5.2 sigma
Photon index:      2.20 (+0.31, -0.30)

If the light curve continues to decay with a power-law decay index of
1.12, the count rate at T+24 hours will be 2.0 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.1 x
10^-13 (2.8 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00657321.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB151001B
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18384
SUBJECT: GRB 151001B: Swift/UVOT Upper Limits
DATE:    15/10/02 18:50:46 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld@ucl.ac.uk>

A. A. Breeveld (UCL-MSSL) and H. A. Krimm (CRESST/GSFC/USRA)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 151001B 
148 s after the BAT trigger (Krimm et al., GCN Circ. 18374).
No optical afterglow consistent with the XRT position (Evans et al. GCN 
Circ. 18377) is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system 
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding 
chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC           148          298          147         >20.6
white              148         6765          805         >21.8
u_FC               307          557          246         >19.9
v                  636         7175          529         >20.2
b                  563         6561          333         >20.9
u                  307        11107          685         >20.7
w1                 686         7585          510         >20.2
m2                 661         7380          529         >20.2
w2                 613         6970          529         >20.6

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 1.71 in the direction of the 
burst (Schlegel et al. 1998).


GRB_name: GRB151001B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18385
SUBJECT: R: GRB 151001B: MASTER-NET early optical observations. 
DATE:    15/10/02 19:05:35 GMT
FROM:    Remo Rufinni at ICRA  <ruffini@icra.it>

Prof. Remo Ruffini
Director of ICRANet
Piazza della Repubblica 10
65122 Pescara (PE)  Italy
mobile: +39 339 4752566
Tel. Rome +39 06 49914304
Tel. Pescara +39 085 23054201
Fax: +39 085 4219252
e-mail: ruffini@icra.it
________________________________________
Da: GCN Circulars [gcncirc@capella2.gsfc.nasa.gov]
Inviato: venerd? 2 ottobre 2015 11.31
A: Remo Ruffini - Icra
Oggetto: GRB 151001B: MASTER-NET early optical observations.

TITLE:   GCN CIRCULAR
NUMBER:  18380
SUBJECT: GRB 151001B: MASTER-NET early optical observations.
DATE:    15/10/02 09:22:48 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov
Blagoveschensk Educational State University, Blagoveschensk

E. Gorbovskoy, V. Lipunov, M.Pruzhinskaya, V.Kornilov, D.Kuvshinov,
N.Tyurina, N.Shatskiy, P.Balanutsa, D.Zimnukhov, A.Kuznetsov, V.V.Chazov,
D.Denisenko,  A.Sankovich
Lomonosov Moscow State University,
Sternberg Astronomical Institute, Moscow State University

K.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk
Irkutsk State University

V.Krushinski, I.Zalozhnih,  A. Popov
Ural Federal University, Kourovka

A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik
Kislovodsk Solar Station of the Pulkovo Observatory

D.Buckley, S. Potter, A.Kniazev, M.Kotze
South African Astronomical Observatory

Hugo Levato and Carlos Saffe
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)

Claudio Mallamaci, Carlos Lopez and Federico Podest
Observatorio Astronomico Felix Aguilar (OAFA)

R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres
The Instituto de Astrofisica de Canarias


MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru)
located in Blagoveschensk was pointed to the  GRB151001B   20 sec after
notice time and 96 sec after trigger time at 2015-10-01 18:31:13 UT. On
our first (20s exposure)  set we haven't found optical transient  within
SWIFT error-box (Krimm et. al GCN 18374).
The 5-sigma upper limit has been about 18.0 mag
The message may be cited.


GRB_name: GRB151001A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18386
SUBJECT: GRB 151001A: RATIR Observations
DATE:    15/10/02 19:25:37 GMT
FROM:    V. Zach Golkhou at ASU/RATIR  <golkhou@gmail.com>

V. Zach Golkhou (ASU), Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Chris 
Klein (UCB), Ori Fox (UCB), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (GSFC/STScI), Eleonora Troja (GSFC), Owen Littlejohns 
(ASU), Enrico Ramirez-Ruiz (UCSC), Jos? A. de Diego (UNAM), Leonid Georgiev (UNAM), Jes?s Gonz?lez (UNAM), Carlos Rom?n-Z??iga (UNAM), Neil 
Gehrels (GSFC), Harvey Moseley (GSFC), John Capone (UMD), and Vicki Toy (UMD) report:

We observed the field of GRB 151001A (Stamatikos, et al., GCN 18373) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on 
the 1.5m Harold Johnson Telescope at the Observatorio Astron?mico Nacional on Sierra San Pedro M?rtir from 2015/10 2.10 to 2015/10 2.15 UTC (11.31 to 
12.60 hours after the BAT trigger), obtaining a total of 1.07 hours exposure in the r, i, and z bands.

For a source within the Swift-XRT error circle (Beardmore et al., GCN 18376), in comparison with the SDSS DR9 catalog, we obtain the following 
detections and upper limit (3-sigma):

   r   =  22.69 +/- 0.20
   i   =  22.59 +/- 0.20
   z   >  20.03

These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. The source has faded by about 1 
magnitude relative to the earlier observations by the NOT (Kruehler, et al. GCN 18379).

We thank the staff of the Observatorio Astron?mico Nacional in San Pedro M?rtir.


GRB_name: GRB151001A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18387
SUBJECT: GRB 151001A: Swift-BAT refined analysis
DATE:    15/10/03 00:12:58 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

M. Stamatikos (OSU), S. D. Barthelmy (GSFC),  J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU),
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 151001A (trigger #657286)
(Stamatikos, et al., GCN Circ. 18373).  The BAT ground-calculated position is
RA, Dec = 233.722, 10.984 deg which is
  RA(J2000)  =  15h 34m 53.2s
  Dec(J2000) = +10d 59' 01.1"
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.

The mask-weighted light curve shows a single-peaked structure that starts
at ~T-6 s, peaks at ~T0, end ends at~T+5 s. T90 (15-350 keV) is 8.94 +- 1.07 sec
(estimated error including systematics).

The time-averaged spectrum from T-6.28 to T+4.53 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.17 +- 0.11.  The fluence in the 15-150 keV band is 6.7 +- 0.5 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-0.04 sec in the 15-150 keV band
is 1.3 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/657286/BA/


GRB_name: GRB151004A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18389
SUBJECT: Swift Trigger 657564: a probable GRB
DATE:    15/10/04 18:19:25 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

S. B. Cenko (GSFC), S. D. Barthelmy (GSFC), D. N. Burrows (PSU),
J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC),
F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester),
D. M. Palmer (LANL), B. Sbarufatti (INAF-OAB/PSU),
E. Troja (NASA/GSFC/UMCP) and T. N. Ukwatta (LANL) report on behalf of
the Swift Team:

At 18:09:04 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 151004A (trigger=657564).  Swift did not slew due to the
Earth-limb observing constraint.  The BAT on-board calculated location is 
RA, Dec 213.585, -64.947, which is 
   RA(J2000)  =  14h 14m 20s
   Dec(J2000) = -64d 56' 49"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is typical for image triggers, the real-time
light curve does not show anything significant. 

Due to an observing constraint, Swift will not slew until T0+56.9
minutes. There will be no XRT or UVOT data until this time. 

Burst Advocate for this burst is S. B. Cenko (brad.cenko AT nasa.gov). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)


GRB_name: GRB151004A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18391
SUBJECT: Swift Trigger 657564: XRT prompt analysis
DATE:    15/10/04 20:15:04 GMT
FROM:    Claudio Pagani at U of Leicester  <cp232@star.le.ac.uk>

C. Pagani (U. Leicester), P. A. Evans (U. Leicester) and S. B. Cenko (GSFC) report on behalf of the Swift-XRT Team:

The XRT began observing the field of the possible GRB 151004A (Swift trigger 657564, Cenko et al., GCN Circ. 18389) at 19:09:14.0 UT, 3609.3 seconds after the BAT trigger. No source was detected in 1.1 ks of promptly downlinked data, which covered 84% of the BAT error circle. We are waiting for the full dataset to detect and localise any possible XRT
counterpart.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB151004A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18393
SUBJECT: Trigger 657564 / GRB 151004A: Swift/UVOT Upper Limits
DATE:    15/10/05 12:13:24 GMT
FROM:    Massimiliano de Pasquale at IASF-Palermo  <m.depasquale@ucl.ac.uk>

M. De Pasquale (UCL-MSSL) and S. B. Cenko (GSFC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of
the trigger 657564 (possible GRB 151004A) 3613 s after the
BAT trigger (Cenko et al., GCN Circ. 18389).
No optical afterglow consistent with the BAT position
is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC          3613         3763          147         >20
white             3613         4994          344         >20.3
v                 3770         5404          393         >18.7
b                 4590         4789          197         >19.2
u                 4384         4584          197         >18.9
w1                4179         4379          197         >19.0
m2                3974         5565          350         >19.3
w2                5000         5200          197         >19.1

The magnitudes in the table are not corrected for the heavy Galactic
extinction due to the reddening of E(B-V) = 1.03 in the direction of
the burst (Schlegel et al. 1998).

-- 

Dr. Massimiliano De Pasquale
Research associate - Swift UVOT scientist
Mullard Space Science Laboratory, University College London


GRB_name: GRB151004A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18396
SUBJECT: Trigger 657564 / GRB 151004A: Swift BAT and XRT refined analysis
DATE:    15/10/05 16:20:49 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

S. D. Barthelmy (GSFC),  S. B. Cenko (GSFC), J. R. Cummings (GSFC/UMBC),
P.A. Evans (U. Leicester), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
A. Y. Lien (GSFC/UMBC), D. Malesani (DARK/NBI), C. B. Markwardt (GSFC),
C. Pagani (U. Leicester), K. L. Page (U. Leicester), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU), and T. N. Ukwatta (LANL)
report on behalf of the Swift team:

Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT trigger 657564 (the probable GRB 151004A;
Cenko et al., GCN Circ. 18389).  The BAT ground-calculated position is
RA, Dec = 213.613, -64.956 deg which is
  RA(J2000)  =  14h 14m 27.1s
  Dec(J2000) = -64d 57' 23.3"
with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.

The BAT mask-weighted light curve shows a weak complex structure that starts
at ~T-10 s and ends at ~T+130 s. T90 (15-350 keV) is 128.40 +- 17.77 sec
(estimated error including systematics).

The BAT time-averaged spectrum from T-13.63 to T+134.42 sec is best fit by
a simple power-law model.  The power law index of the time-averaged spectrum
is 1.95 +- 0.23.  The fluence in the 15-150 keV band is 1.0 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+50.86 sec in the 15-150 keV band
is 0.4 +- 0.1 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

In the BAT energy band, the spectral properties and T90 are consistent with
those of a GRB. However, due to the low Galactic latitude (b = -3.47 deg),
we cannot rule out a Galactic origin.

The XRT began observing at 19:09:14.0 UT, 3610 seconds after the BAT trigger.
In 5.7 ks of Photon Counting (PC) data one faint X-ray source is detected inside
the BAT error circle. The astrometrically corrected X-ray position of the source
(using the XRT-UVOT alignment and matching UVOT field sources to the
USNO-B1 catalogue) is: RA, Dec = 213.63218, -64.93914 which is equivalent to:

RA (J2000): 14h 14m 31.72s
Dec (J2000): -64d 56' 20.9"

with an uncertainty of 7.0 arcsec (radius, 90% confidence). Position enhancement is
described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177).

The X-ray source is faint, at an average count rate of ~0.005 cnts/sec, below
the RASS 3-sigma limit at this position in the sky. If the source is indeed the
X-ray afterglow of GRB 151004A, it would be one of the faintest ever observed
by the XRT at that time after the GRB trigger. At this time, there is only marginal
evidence (1.5 sigma) of fading in the X-ray lightcurve and additional observations
are required to establish the nature of the source.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/657564/BA/


GRB_name: GRB151006A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18398
SUBJECT: GRB 151006A: Swift detection of a burst
DATE:    15/10/06 10:05:37 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

D. Kocevski (NASA/GSFC/ORAU), S. D. Barthelmy (GSFC),
P. A. Evans (U Leicester), K. L. Page (U Leicester) and
B. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift Team:

At 09:55:01 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 151006A (trigger=657750).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 147.451, +70.509, which is 
   RA(J2000)  =  09h 49m 48s
   Dec(J2000) = +70d 30' 31"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a single FRED-like peak
structure with a duration of about 40 sec.  The peak count rate
was ~4000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 09:55:50.4 UT, 48.6 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 147.4256, 70.5036 which is equivalent to:
   RA(J2000)  = +09h 49m 42.14s
   Dec(J2000) = +70d 30' 13.0"
with an uncertainty of 4.8 arcseconds (radius, 90% containment). This
location is 36 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy. 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 58 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
The 8'x8' region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.24. 

Burst Advocate for this burst is D. Kocevski (dankocevski AT gmail.com). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)


GRB_name: GRB151006A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18399
SUBJECT: GRB 151006A: Prompt enhanced Swift-XRT position
DATE:    15/10/06 10:23:24 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:

Using  promptly downlinked XRT event data for GRB 151006A, we find an
enhanced XRT position of the afterglow: RA, Dec: 147.4260, 70.5027
which is equivalent to:
   RA (J2000)  = 09 49 42.25
   Dec (J2000) = +70 30 09.7
with an uncertainty of 2.3 arcseconds (radius, 90% confidence).
Analysis of the promptly available data is online at
http://www.swift.ac.uk/sper/657750.

Position enhancement is is described by Goad et al. (2007, A&A, 476,
1401) and Evans et al. (2009, MNRAS, 397, 1177).

This circular is an official product of the Swift-XRT team.


GRB_name: GRB151006A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18400
SUBJECT: GRB 151006A: Kanata/HOWPol optical imaging polarimetry
DATE:    15/10/06 11:05:12 GMT
FROM:    Koji Kawabata at HASC,Hiroshima U  <kawabtkj@hiroshima-u.ac.jp>

K. S. Kawabata, R. Itoh, M. Kawabata, T. Nakaoka, H. Mori, K. Takaki (Hiroshima 
Univ.), and R. Shimotani (Kagawa Univ.) report on behalf of Kanata team:

We performed a series of optical imaging-polarimetry for the optical afterglow 
of GRB151006A (Kocevski et al., GCN 18398) from 73 sec after the Swift/BAT 
trigger with HOWPol attached to the 1.5-m Kanata telescope at Higashi-Hiroshima
Observatory, Japan.

We could not detect any afterglow within the XRT error circle reported in the 
GCN 18398. We obtained the following preliminary upper limits in our first 
image (mid-time 88 sec after the trigger) calibrated with UCAC4:

Rc > 17.7

Further analysis is ongoing.


GRB_name: GRB151001B
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18401
SUBJECT: Konus-Wind observation of GRB 151001B
DATE:    15/10/06 11:18:10 GMT
FROM:    Anna Kozlova at Ioffe Institute  <ann_kozlova@mail.ioffe.ru>

S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lysenko, A. Kozlova,
and T. Cline on behalf of the Konus-Wind team, report:

At ~16 minutes before the Swift-BAT trigger on GRB 151001B
(Krimm, et al., GCN Circ. 18374; T0(BAT)=18:29:36 UT)
Konus-Wind detected, in the waiting mode, a burst of high X-ray/soft
gamma-ray emission which had a duration of ~191 s.

Taking into account the proximity of this burst to the Swift-BAT trigger
and consistency of the KW ecliptic latitude response with the position
of GRB 151001B we suggest this burst is the main part of GRB 151001B.

The K-W light curve of this burst is available at
http://www.ioffe.ru/LEA/GRBs/GRB151001B/
The count rate increase in the soft KW energy band, which follows the
burst from T0(BAT)-838 s to T0(BAT)+2488 s, can not be unambiguously
attributed to GRB 151001B.

As observed by Konus-Wind, the burst had a fluence of
8.5(-2.3,+0.6)x10^-6 erg/cm2 and a 2.944-s peak flux,
measured from ~T0(BAT)-1007.1 s, of 1.8(-0.6,+0.4)x10^-7 erg/cm2/s
(both in the 20 - 1000 keV energy range).

Modeling the K-W 3-channel time-integrated spectrum
(from T0(BAT)-1018.9 s to T0(BAT)-827.5 s)
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
yields alpha = -0.9(-0.3,+0.5) and Ep = 179 (-52,+75) keV.

All the quoted errors are at 1 sigma confidence level.
All the quoted values are preliminary.


GRB_name: GRB151006A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18402
SUBJECT: GRB 151006A: MITSuME Okayama upper limits
DATE:    15/10/06 11:52:48 GMT
FROM:    Daisuke Kuroda at OAO/NAOJ  <dikuroda@oao.nao.ac.jp>

D. Kuroda, K. Yanagisawa, Y. Shimizu, H. Toda (OAO, NAOJ),
S. Nagayama (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto)
and N. Kawai(Tokyo Tech)
report on behalf of MITSuME and OISTER collaboration:

We observed the field of GRB 151006A (Kocevski et al., GCNC 18398)
with the optical three color (g', Rc and Ic) CCD camera attached
to the MITSuME 50cm telescope of Okayama Astrophysical Observatory.

The observation started on 2015-10-06 09:56:35 UT (~93 sec after the burst).
We did not find any new point source within the enhanced XRT error circle
(Evans, GCNC 18399) in all the three bands.


Three sigma upper limits of the OT are listed below.
We used GSC2.3 catalog for flux calibration.

#T0+[day]  MID-UT    T-EXP[sec]   g'     Rc     Ic
-----------------------------------------------------
0.00707    10:05:12     540.0   >18.6  >18.6  >18.0
-----------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]


GRB_name: GRB151006A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18403
SUBJECT: GRB 151006A: Enhanced Swift-XRT position
DATE:    15/10/06 14:08:27 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 2266 s of XRT Photon Counting mode data and 5 UVOT
images for GRB 151006A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 147.42592, +70.50299 which is equivalent
to:

RA (J2000): 09h 49m 42.22s
Dec (J2000): +70d 30' 10.8"

with an uncertainty of 1.7 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.


GRB_name: GRB151006A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18404
SUBJECT: GRB 151006A: Fermi GBM detection
DATE:    15/10/06 16:02:36 GMT
FROM:    Oliver Roberts at UCD/Fermi  <oliver.roberts@ucd.ie>

O.J. Roberts (UCD) and C.Meegan (UAH) report on
behalf of the Fermi GBM Team:

"At 09:54:57.83 UT on 06 October 2015, the Fermi
Gamma-Ray Burst Monitor triggered and located
GRB 151006A (trigger 465818101/151006413), which
was also detected by Swift BAT and XRT
(Kocevski et al. 2015, GCN 18398). The GBM on-ground
location is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM
trigger time using the Swift position is 30 degrees.

The GBM light curve consists of a FRED-like peak
with a duration (T90) of about 84 s (50-300 keV).
The time-averaged spectrum from T0+0 s to T0+83.7 s
is best fit by a Band function with Epeak = 227 +/- 53 keV,
alpha = -1.17 +/- 0.07, and beta = -1.68 +/- 0.04

The event fluence (10-1000 keV) in this time interval
is (1.15 +/- 0.02)E-05 erg/cm^2. The 1-sec peak photon
flux measured starting from T0+5.24 s in the 10-1000 keV
band is 4.9 +/- 0.2 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."


GRB_name: GRB151006A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18405
SUBJECT: GRB 151006A: Swift/UVOT Upper Limits
DATE:    15/10/06 19:03:04 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld@ucl.ac.uk>

A. A. Breeveld (UCL-MSSL) and D. Kocevski (NASA/GSFC/ORAU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 151006A 36 
s after the BAT trigger (Kocevski et al., GCN Circ. 18398).
No optical afterglow consistent with the XRT position (Goad et al. GCN 
Circ. 18403) is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system 
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding 
chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC            58          208          147         >20.7
u_FC               271          521          246         >19.9
white               58         6351          520         >21.4
v                   36         6754          437         >19.8
b                  527         6146          236         >20.3
u                  271         5941          442         >20.3
w1                5537         5736          197         >19.8
m2                 625         5531          235         >19.7
w2                 577         6557          432         >20.4

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.24 in the direction of the 
burst (Schlegel et al. 1998).


GRB_name: GRB151006A
Detection_method: Fermi LAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18406
SUBJECT: GRB 151006A: Fermi-LAT detection
DATE:    15/10/06 21:13:33 GMT
FROM:    Daniel Kocevski at GSFC  <daniel.kocevski@nasa.gov>

M. Ohno (Hiroshima U.), E. Bissaldi (INFN Bari), G. Vianello (Stanford University),
D. Kocevski (NASA/GSFC)  and F. Longo (University & INFN Trieste)
report on behalf of the Fermi-LAT team:

At 09:54:57.83 on October 06, 2015, Fermi-LAT detected  high-energy emission
from GRB 151006A, which was also detected by Fermi-GBM (trigger 465818101;
Roberts et al. GCN 18404)  and Swift-BAT  (Kocevski et al. GCN 18398).

The GBM location was initially inside the LAT field of view  at an angle of ~30 degrees
to the LAT boresight.  Using the LAT Low Energy (LLE) data selection, over 400 counts above
background were detected within a 30 s interval coinciding with the time of the GBM emission.
This data selection has insufficient spatial resolution to provide a reliable LAT localization.
Processing and analysis of standard data is ongoing.

The Fermi LAT point of contact for this burst is
Masanori Ohno (ohno@hep01.hepl.hiroshima-u.ac.jp<mailto:ohno@hep01.hepl.hiroshima-u.ac.jp>).

The Fermi-LAT is a pair conversion telescope designed to cover
the energy band from 20 MeV to greater than 300 GeV.
It is the product of an international collaboration between
NASA and DOE in the U.S. and many scientific institutions
across France, Italy, Japan and Sweden.


GRB_name: GRB151006A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18407
SUBJECT: GRB 151006A: Swift-XRT refined Analysis
DATE:    15/10/06 22:05:02 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

L.M. McCauley (PSU), J.A. Kennea (PSU), A.P. Beardmore (U. Leicester),
P.A. Evans (U. Leicester), S.L. Gibson (U. Leicester), V. D'Elia
(ASDC), A. D'ai (INAF-IASFPA), A. Maselli  (INAF-IASFPA), B. Sbarufatti
(INAF-OAB/PSU) and D. Kocevski report on behalf of the Swift-XRT team:

We have analysed 11 ks of XRT data for GRB 151006A (Kocevski et al. GCN
Circ. 18398), from 40 s to 29.1 ks after the  BAT trigger. The data
comprise 552 s in Windowed Timing (WT) mode (the first 7 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Goad et al.
(GCN Circ. 18399).

The light curve can be modelled with an initial power-law decay with an
index of alpha=0.3 (+0.7, -1.6), followed by a break at T+64.1 s to an
alpha of 1.377 (+0.020, -0.019).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.45 (+0.06, -0.05). The
best-fitting absorption column is  4.9 (+0.5, -0.4) x 10^21 cm^-2, in
excess of the Galactic value of 7.7 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 2.08 (+0.17, -0.16)
and a best-fitting absorption column of 4.3 (+0.9, -0.8) x 10^21 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 3.7 x 10^-11 (6.1 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      4.3 (+0.9, -0.8) x 10^21 cm^-2
Galactic foreground: 7.7 x 10^20 cm^-2
Excess significance: 7.1 sigma
Photon index:      2.08 (+0.17, -0.16)

If the light curve continues to decay with a power-law decay index of
1.377, the count rate at T+24 hours will be 4.7 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.7 x
10^-13 (2.9 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00657750.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB151006A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18408
SUBJECT: GRB 151006A: MITSuME Okayama Ks-band upper-limit
DATE:    15/10/07 02:58:46 GMT
FROM:    Kenshi Yanagisawa at OAO/NAOJ  <yanagi@oao.nao.ac.jp>

Kenshi Yanagisawa, Daisuke Kuroda, Yasuhiro Shimizu,
Hideyuki Izumiura(OAO/NAOJ), Michitoshi Yoshida (Hiroshima-U),
Kouji Ohta(Kyoto-U) and Nobuyuki Kawai(Tokyo Tech.) report
on behalf of the MITSuME collaboration:

We observed the field of GRB151006A (Kocevski et al., GCN 18398)
in Ks-band with a wide-field near infrared imager at Okayama
Astrophysical Observatory (Japan).  The imager has effective
aperture of 0.91 m.

Observations started from 17:22 UT on 6th October, 7.4h after
the BAT trigger, to 18:17 UT. The total exposure of 26.5 min
was successfully obtained.

In our co-add image, we did not find any new point source within
the enhanced XRT error circle (Goad et al., GCN 18403) down
to limiting magnitude of Ks=15.2 (Vega, S/N=10). The photometric
calibration was made against 2MASS field stars.

T0+[sec]    MID-UT     T-EXP[sec]      Ks
---------------------------------------------------
 +26,819    17:49      1,590           >15.2
---------------------------------------------------
T0+ : Elapsed time after the burt [sec]
T-EXP: Total Exposure time [sec]


GRB_name: GRB151006A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18409
SUBJECT: GRB 151006A: Swift-BAT refined analysis
DATE:    15/10/07 15:19:37 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC),  N. Gehrels (GSFC),
D. Kocevski (NASA/GSFC/ORAU), H. A. Krimm (GSFC/USRA),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-239 to T+800 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 151006A (trigger #657750)
(Kocevski, et al., GCN Circ. 18398).  The BAT ground-calculated position is
RA, Dec = 147.426, 70.508 deg which is
  RA(J2000)  =  09h 49m 42.3s
  Dec(J2000) = +70d 30' 30.2"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.

The mask-weighted light curve shows a FRED-like structure that starts at ~T-5 s,
peaks at ~ T+1 s, and ends at ~ T+310 s. T90 (15-350 keV) is 203.9 +- 41.6 sec
(estimated error including systematics).

The time-averaged spectrum from T-4.9 to T+311.2 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.56 +- 0.06.  The fluence in the 15-150 keV band is 6.9 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+1.49 sec in the 15-150 keV band
is 2.6 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/657750/BA/


GRB_name: GRB151006A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18410
SUBJECT: GRB 151006A: Swift-BAT refined analysis
DATE:    15/10/07 15:40:03 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC),  N. Gehrels (GSFC),
D. Kocevski (NASA/GSFC/ORAU), H. A. Krimm (GSFC/USRA),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-239 to T+800 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 151006A (trigger #657750)
(Kocevski, et al., GCN Circ. 18398).  The BAT ground-calculated position is
RA, Dec = 147.426, 70.508 deg which is
  RA(J2000)  =  09h 49m 42.3s
  Dec(J2000) = +70d 30' 30.2"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.

The mask-weighted light curve shows a FRED-like structure that starts at ~T-5 s,
peaks at ~ T+1 s, and ends at ~ T+310 s. T90 (15-350 keV) is 203.9 +- 41.6 sec
(estimated error including systematics).

The time-averaged spectrum from T-4.9 to T+311.2 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.56 +- 0.06.  The fluence in the 15-150 keV band is 6.9 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+1.49 sec in the 15-150 keV band
is 2.6 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/657750/BA/


GRB_name: GRB151006A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18411
SUBJECT: GRB 151006A: OSN optical upper limit
DATE:    15/10/07 17:43:58 GMT
FROM:    Samantha Oates at MSSL  <sro@mssl.ucl.ac.uk>

S. R. Oates (IAA-CSIC), S. Jeong (IAA-CSIC/SKKU), A. Sota, J. C. Tello (IAA-CSIC),
A.J. Castro-Tirado (IAA-CSIC/UMA), S. B. Pandey (ARIES Nainital) report on behalf
of a larger collaboration:

We observed the field of GRB 151006A (Kocevski et al., GCN Circ. 18398) with the 1.5m
OSN telescope at Observatorio de Sierra Nevada (Spain). The observations
were carried out in the I band on Oct 7.13159-7.17369 (17.24 - 18.25 hours
post bust). We do not detect any new optical source within the enhanced XRT 
error circle (Goad et al., GCN Circ. 18403) down to a limiting magnitude of I ~21mag.


GRB_name: GRB151006A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18413
SUBJECT: Konus-Wind observation of GRB 151006A
DATE:    15/10/08 11:04:52 GMT
FROM:    Anastasia Tsvetkova at Ioffe Institute  <tsvetkova@mail.ioffe.ru>

S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, A. Kozlova and T. Cline
on behalf of the Konus-Wind team, report:

The long-duration, hard-spectrum GRB 151006A
(Swift-BAT trigger #657750: Kocevski et al., GCN 18398;
Cummings  et al., GCN 18409;
Fermi GBM detection: Roberts & Meegan, GCN 18404)
triggered Konus-Wind at T0=35697.746 s UT (09:54:57.746).

The burst light curve shows a single FRED-like pulse
with a total duration of ~114 s.
The emission is seen up to ~10 MeV.

As observed by Konus-Wind, the burst
had a fluence of 5.30(-0.87,+0.92)x10^-5 erg/cm2,
and a 64-ms peak energy flux, measured from T0+2.928 s,
of 5.60(-2.26,+2.23)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the burst
(measured from T0 to T0+73.984 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -1.26(-0.23,+0.42),
the high energy photon index beta = -1.73(-0.13,+0.09),
the peak energy Ep = 223(-132,+514) keV,
chi2 = 85/97 dof.

The spectrum near the peak count rate
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 15 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -1.40(-0.06,+0.07),
and Ep = 2600(-1200,+2900) keV (chi2 = 71/98 dof).
Fitting by the GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index:
beta < -1.7 (chi2 = 71/97 dof).

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB151006_T35697/

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.


GRB_name: GRB151006A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18415
SUBJECT: GRB 151006A: MITSuME Akeno optical upper limits
DATE:    15/10/09 13:37:39 GMT
FROM:    Taketoshi Yoshii at Tokyo Tech  <yoshii.t.ac@m.titech.ac.jp>

S.Harita, T.Fujiwara, T. Yoshii, Y. Saito, Y. Tachibana, H. Ohuchi, Y. Yano,
S. Kurita, Y.Ono, Y.Muraki, Y. Yatsu, and N. Kawai (Tokyo Tech)


report on behalf of the MITSuME collaboration:

We searched for the optical counterpart of GRB 151006A (D. Kocevski et al. GCN Circular #18398) with the
optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope of Akeno Observatory, Yamanashi, Japan.

The observation started on 2015-10-06 15:20:15 UT (~4.4 h after the burst).
We did not find any new point source within XRT circle in all three bands.

We obtained following limits for the magnitudes.

T0+[sec]      MID-UT      T-EXP[sec]         g'           Rc           Ic
---------------------------------------------------------------------------------------
  19514     17:24:12.2          9240           >21.3      >20.8     > 19.9
---------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used GSC2.3 catalog for flux calibration


GRB_name: GRB151006A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18416
SUBJECT: GRB 151006A: Mondy optical upper limit
DATE:    15/10/11 10:03:30 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

E. Mazaeva (IKI), E. Klunko (ISTP), A. Volnova (IKI), I. Korobtsev 
(ISTP),  A. Pozanenko (IKI) report on behalf of larger GRB follow-up 
collaboration:

We observed the field of Swift GRB 151006A (Kocevski et al., GCN 18398) 
with AZT-33IK telescope of Sayan observatory (Mondy) starting on Oct. 18 
(UT) 16:50:47. We obtained several images in R-filter of 120 s exposure. 
    Within XRT error circle (Goad et al., GCN 18403)  we do not detect 
any optical source. Upper limit is following

Date       UT start   t-T0     Filter   Exp.    UL (3 sigma)
                       (mid, days)       (s)

2015-10-06 16:50:47   0.31306  R        35*120  22.4

Photometry is based on USNO-B1.0 stars:
USNO-B1.0_id R2
1604-0085829 18.23
1604-0085812 16.90


GRB_name: GRB151006A
Detection_method: AstroSat CZTI
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18422
SUBJECT: GRB 151006A: Astrosat CZTI detection
DATE:    15/10/16 11:28:09 GMT
FROM:    Varun Bhalerao at IUCAA  <varunb@iucaa.in>

V. Bhalerao (IUCAA), D. Bhattacharya (IUCAA), A. R. Rao (TIFR), S. Vadawale (PRL) report on behalf of the Astrosat CZTI collaboration:

Analysis of Astrosat commissioning data showed the presence of GRB 151006A (Kocevski et al. 2015, GCN 18398) in the Cadmium Zinc Telluride Imager. The source was located 60.7 degrees away from the pointing direction and was detected at energies above 60 keV. Modelling the profile as a fast rise and exponential decay, we measure T90 of 65s, 75s, and 50s in 60-80 keV, 80-100 keV and 100-250 keV bands respectively.

In addition, the GRB is clearly detected in a lightcurve created from double events satisfying Compton scattering criteria (Vadawale et al., 2015, A&A, 578, 73). This demonstrates the feasibility of measuring polarisation for brighter GRBs with CZTI.


GRB_name: GRB151004A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18423
SUBJECT: GRB 151004A: Swift-XRT follow-up observations
DATE:    15/10/16 13:25:03 GMT
FROM:    Claudio Pagani at U of Leicester  <cp232@star.le.ac.uk>

C. Pagani, K. L. Page, P. A. Evans (U. Leicester) and S. B. Cenko (GSFC) 
report on behalf of the Swift-XRT team:

A second epoch of XRT data was collected on the field of the Swift 
Trigger 657564 / GRB 151004A (Cenko et al., GCN Circ. 18389) on 2015 
October 15. The observations consist of 7.7 ks of PC mode data, from 
T0+885 ks to T0+932 ks.

The candidate X-ray source reported in Barthelmy et al., GCN Circ. 
18396, originally detected at a count rate of 4.8 (+/- 1.14) x 10^-3 
cnts/sec (0.3-10 keV) is not detected in this second epoch of 
observations, with a 3 sigma upper limit of 1.5 x 10^-3 cnts/sec (0.3-10 
keV). The fading confirms that this is the X-ray afterglow of the Swift 
Trigger 657564 / GRB 151004A.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB151021A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18425
SUBJECT: GRB 151021A: Swift detection of a burst
DATE:    15/10/21 02:05:25 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

A. Melandri (INAF-OAB), S. D. Barthelmy (GSFC),
P. D'Avanzo (INAF-OAB), H. A. Krimm (CRESST/GSFC/USRA),
N. P. M. Kuin (UCL-MSSL), D. M. Palmer (LANL) and
B. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift Team:

At 01:29:12 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 151021A (trigger=660671).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 337.611, -33.199 which is 
   RA(J2000) = 22h 30m 27s
   Dec(J2000) = -33d 11' 55"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex multi-peaked
structure with a duration of at least 100 sec.  The peak count rate
was 2500 counts/sec (15-350 keV), at 10 sec after the trigger,
although the lightcurve around the time of trigger is not
immediately available. 

The XRT began observing the field at 01:30:43.2 UT, 90.7 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 337.64619, -33.19907 which
is equivalent to:
   RA(J2000)  = 22h 30m 35.09s
   Dec(J2000) = -33d 11' 56.7"
with an uncertainty of 3.6 arcseconds (radius, 90% containment). This
location is 106 arcseconds from the BAT onboard position, within the
BAT error circle. This position may be improved as more data are
received; the latest position is available at
http://www.swift.ac.uk/sper. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column destiny in excess of the Galactic value (1.13 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 3.9
(+2.55/-2.23) x 10^21 cm^-2 (90% confidence). 

The initial flux in the 0.1 s image was 2.76e-08 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 99 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 8'x8' region for the list of 
sources generated on-board covers 100% of the XRT error circle. The list 
of sources is typically complete to about 18 mag. No correction has 
been made for the expected extinction corresponding to E(B-V) of 0.01. 

Burst Advocate for this burst is A. Melandri (andrea.melandri AT brera.inaf.it). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)


GRB_name: GRB151021A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18426
SUBJECT: GRB 151021A: Optical counterpart and redshift from X-shooter
DATE:    15/10/21 03:53:02 GMT
FROM:    Antonio de Ugarte Postigo at IAA-CSIC  <deugarte@iaa.es>

A. de Ugarte Postigo, (IAA-CSIC, DARK/NBI), D. Malesani (DARK/NBI),
D. Xu (NAOC/CAS) report on behalf of a larger collaboration:

We have observed the field of GRB 151021A (Melandri et al., GCN 18425) 
with X-shooter at the VLT (Paranal Observatory, Chile). Observation 
started at 02:13 UT (44 min after the burst) and cover the range between
3000 and 24800 AA.

In the close proximity of the XRT error circle, we detect a bright, uncatalogued 
object in the r'-band acquisition image, at coordinates (J2000, 0.5" error):

RA = 22:30:34.369
Dec = -33:11:49.45

We suggest that this is the optical afterglow of GRB 151021A and we measure 
for it R = 18.2 (Vega), derived from comparison with R-band magnitudes for the 
USNO-B1.0 catalogue. An object at consistent coordinates is also visible in the 
UVOT white-band image.

On a preliminary reduction, the spectrum shows a bright continuum with multiple 
absorption features, including SII, OI, SiII, SiIV, CIV, AlII, ZnII, CrII, FeII, NiII, MnII, 
MgII, MgI, as well as fine-structure lines from FeII* and NiII* and Ly-alpha 
absorption at a common redshift of z = 2.330, which we identify as the redshift of 
the GRB. We also identify an intervening system at z = 1.490 with features of 
FeII, MgII, and MgI.

We acknowledge the excellent support given by the Paranal staff, and in 
particular Andrea Mehner, Julien Mili and Jose Velasquez.


GRB_name: GRB151021A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18427
SUBJECT: GRB 151021A: MASTER-NET bright OT detection
DATE:    15/10/21 06:46:01 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy,   N.Tyurina, V.Kornilov, P.Balanutsa,
A.Kuznetsov, D.Kuvshinov, D. Vlasenko
Lomonosov Moscow State University, Sternberg Astronomical Institute

D.Buckley, S. Potter, A.Kniazev, M.Kotze
South African Astronomical Observatory

K.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk
Irkutsk State University

A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik
Kislovodsk Solar Station of the Pulkovo Observatory

V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov
Blagoveschensk Educational State University, Blagoveschensk


V.Krushinski, I.Zalozhnih,  A. Popov
Ural Federal University, Kourovka

Hugo Levato and Carlos Saffe
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)

Claudio Mallamaci, Carlos Lopez and Federico Podest
Observatorio Astronomico Felix Aguilar (OAFA)



MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in SAAO was pointed to the  GRB151021A 25 sec after notice time 
and 50 sec after trigger time at 2015-10-21 01:30:06 UT in two 
polarizations. On our first (10s exposure)  set we  found 1 optical 
transient within SWIFT error-box (Melandri et. al GCN 18425) brighter then 
16.


date       time      Tmid-T0      Coord2000                       Mag
2015-10-21 01:30:06   55.0   (22h 30m 34.42s , -33d 11m 50.3s)    14.86

The 5-sigma upper limit has been about 16.0 mag
The message may be cited.

[GCN OPS NOTE(21oct15) Per author's request, the GBB name in the Subject-line
was changed from 0921A to 1021A.]


GRB_name: GRB151021A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18428
SUBJECT: GRB 151021A: Enhanced Swift-XRT position
DATE:    15/10/21 08:25:17 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 2547 s of XRT Photon Counting mode data and 3 UVOT
images for GRB 151021A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 337.64347, -33.19731 which is equivalent
to:

RA (J2000): 22h 30m 34.43s
Dec (J2000): -33d 11' 50.3"

with an uncertainty of 1.7 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.


GRB_name: GRB151021A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18429
SUBJECT: GRB 151021A: Swift-BAT refined analysis
DATE:    15/10/21 11:43:31 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>

H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
A. Melandri (INAF-OAB), D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
 
Using the data set from T-240 to T+352 sec from the recent telemetry downlinks,
we report further analysis of BAT GRB 151021A (trigger #660671)
(Melandri, et al., GCN Circ. 18425).  The BAT ground-calculated position is
RA, Dec = 337.647, -33.189 deg, which is 
   RA(J2000)  =  22h 30m 35.3s 
   Dec(J2000) = -33d 11' 21.8" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 10%.
 
The mask-weighted light curve shows many overlapping peaks starting
at ~T-50sec, with a maxiximum peak at ~T+1 sec, and ending at ~T+130 sec.
T90 (15-350 keV) is 110.2 +- 3.7 sec (estimated error including systematics).
 
The time-averaged spectrum from T-21.6 to T+127.4 sec (with a 1.5 sec data gap
in the middle) is best fit by a simple power-law model.  The power law index
of the time-averaged spectrum is 1.57 +- 0.04.  The fluence in the 15-150 keV band
is 2.8 +- 0.1 x 10^-5 erg/cm2.  The 1-sec peak photon flux measured from T-0.13 sec
in the 15-150 keV band is 9.7 +- 0.8 ph/cm2/sec.  All the quoted errors are
at the 90% confidence level. 
 
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/660671/BA/


GRB_name: GRB151021A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18430
SUBJECT: GRB 151021A: Swift-XRT refined Analysis
DATE:    15/10/21 14:05:03 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

J.A. Kennea (PSU), P.A. Evans (U. Leicester), S.L. Gibson (U.
Leicester), J.P. Osborne (U. Leicester), A. D'ai (INAF-IASFPA), A.
Maselli  (INAF-IASFPA), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows
(PSU) and A. Melandri report on behalf of the Swift-XRT team:

We have analysed 6.7 ks of XRT data for GRB 151021A (Melandri et al.
GCN Circ. 18425), from 80 s to 29.2 ks after the  BAT trigger. The data
comprise 184 s in Windowed Timing (WT) mode (the first 9 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Osborne et
al. (GCN Circ. 18428).

The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=1.3 (+1.8, -1.6). At T+102 s  the decay
steepens to an alpha of 3.90 (+0.33, -0.29). The light curve breaks
again at T+230 s to a decay with alpha=0.91 (+0.07, -0.06),  before a
final break at T+2618 s s after which the decay index is 1.40
(+/-0.08).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.68 (+/-0.04). The
best-fitting absorption column is  1.47 (+0.20, -0.19) x 10^22 cm^-2,
at a redshift of 2.33, in addition to the Galactic value of 1.1 x 10^20
cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index
of 1.96 (+0.10, -0.09) and a best-fitting absorption column of 2.3
(+0.5, -0.4) x 10^22 cm^-2. The counts to observed (unabsorbed) 0.3-10
keV flux conversion factor deduced from this spectrum  is 3.5 x 10^-11
(4.4 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Galactic foreground: 1.1 x 10^20 cm^-2
Intrinsic column:    2.3 (+0.5, -0.4) x 10^22 cm^-2 at z=2.33
Photon index:      1.96 (+0.10, -0.09)

If the light curve continues to decay with a power-law decay index of
1.40, the count rate at T+24 hours will be 0.017 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.9 x
10^-13 (7.5 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00660671.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB151021A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18431
SUBJECT: GRB 151021A: MITSuME Okayama upper limits
DATE:    15/10/21 14:24:07 GMT
FROM:    Daisuke Kuroda at OAO/NAOJ  <dikuroda@oao.nao.ac.jp>

D. Kuroda, K. Yanagisawa, Y. Shimizu, H. Toda (OAO, NAOJ),
S. Nagayama (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto)
and N. Kawai(Tokyo Tech)
report on behalf of MITSuME and OISTER collaboration:

We observed the field of GRB 151021A (Melandri et al., GCNC 18425)
with the optical three color (g', Rc and Ic) CCD camera attached
to the MITSuME 50cm telescope of Okayama Astrophysical Observatory.

The observation started on 2015-10-21 09:35:46 UT (8.1 h after
the burst). We could not detect the previously reported afterglow
(de Ugarte Postigo et al., GCNC 18426; Lipunov et al., GCNC 18427)
in all the three bands.

Three sigma upper limits of the OT are listed below.
We used GSC2.3 catalog for flux calibration.

#T0+[day]  MID-UT    T-EXP[sec]   g'    Rc     Ic
-----------------------------------------------------
0.37964    10:35:52    6180.0   >19.5  >19.7  >19.1
-----------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]


GRB_name: GRB151021A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  18432
SUBJECT: GRB 151021A: Swift/UVOT Detection
DATE:    15/10/21 15:44:32 GMT
FROM:    Marissa McCaule at PSU  <marissamc@swift.psu.edu>

L. M. McCauley (PSU), and A. Melandri (INAF-OAB)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 151021A
99 s after the BAT trigger (Melandri et al., GCN Circ. 18425).
A source consistent with the XRT position
(Osborne et al. GCN Circ. 18428)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  22:30:34.43 = 337.64335 (deg.)
    Dec (J2000) = -33:11:50.3  = -33.19715 (deg.)
with an estimated uncertainty of 0.42 arc sec. (radius, 90% confidence).

Preliminary detections and 3-sigma upper limits using the UVOT photometric
system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures
are:

Filter         T_start(s)   T_stop(s)   Exp(s)     Mag

white                  99         249      294   16.89
white                1668        5949      216  >20.86
v                      81          90        9   15.82
v                    1545        6359      235  >19.28
b                    1644        5744      216  >20.19
u                    1619        5538      216  >19.77
uvw1                 5133        5333      196  >19.53
uvm2                 4928        7484      316  >19.64
uvw2                 5955        6155      196  >19.97


The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.01 in the direction of the burst
(Schlegel et al. 1998).


