# GCN_circulars

GRB_name: GRB160227A
Detection_method: MAXI Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19103
SUBJECT: GRB 160227A: MAXI/GSC detection
DATE:    16/02/28 04:50:29 GMT
FROM:    H. Negoro at Nihon U.  <negoro@phys.cst.nihon-u.ac.jp>

T. Yoshii (Tokyo Tech), M. Nakajima, H. Negoro (Nihon U.),
S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, Y. E. Nakagawa (JAXA),
T. Mihara, M. Sugizaki, M. Serino, M. Shidatsu, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN),
N. Kawai, M. Arimoto, Y. Tachibana, Y. Ono, T. Fujiwara (Tokyo Tech),
A. Yoshida, T. Sakamoto, Y. Kawakubo, H. Ohtsuki (AGU),
H. Tsunemi, R. Imatani (Osaka U.),
K. Tanaka, T. Masumitsu (Nihon U.),
Y. Ueda, T. Kawamuro, T. Hori, A. Tanimoto (Kyoto U.),
Y. Tsuboi, S. Kanetou, Y. Nakamura, R. Sasaki (Chuo U.),
M. Yamauchi, D. Itoh, K. Furuya (Miyazaki U.),
K. Yamaoka (Nagoya U.),
M. Morii (ISM)

report on behalf of the MAXI team:

The MAXI/GSC detected an uncatalogued X-ray transient source at 19:35:13 UT on 2016 February 27.
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (192.924 deg, 78.686 deg) = (12 51 41, +78 41 09) (J2000)
with a statistical 90% C.L. elliptical error region
with long and short radii of 0.39 deg and 0.38 deg, respectively.
The roll angle of long axis from the north direction is 46.0 deg counterclockwise.
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 130 +- 27 mCrab
(4-10keV, 1 sigma error).
Without assumptions on the source constancy,we obtain a rectangular error
box for the transient source with the following corners:
(R.A., Dec) = (197.530 deg, 78.335 deg) = (13 10 07, +78 20 05) (J2000)
(R.A., Dec) = (194.899 deg, 77.788 deg) = (12 59 35, +77 47 15) (J2000)
(R.A., Dec) = (185.390 deg, 79.282 deg) = (12 21 33, +79 16 55) (J2000)
(R.A., Dec) = (187.705 deg, 79.931 deg) = (12 30 49, +79 55 52) (J2000)

The position is consistent with that of GRB 160227A (Siegel et al., GCN 19098),
and the detected time is 185 sec after the BAT trigger.

There was no significant excess flux in the previous transit at 
18:02 UT on 2016 February 27 and in the next transit at 
21:07 UT on 2016 February 27 with an upper limit of 20 mCrab for each.


GRB_name: GRB160227A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19104
SUBJECT: GRB 160227A: Enhanced Swift-XRT position
DATE:    16/02/28 05:23:00 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 1604 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 160227A, 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 = 194.80719, +78.67917 which is equivalent
to:

RA (J2000): 12h 59m 13.73s
Dec (J2000): +78d 40' 45.0"

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: GRB160227A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19105
SUBJECT: GRB 160227A: Swift-XRT refined Analysis
DATE:    16/02/28 08:25:09 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P.A. Evans (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), S.L. Gibson (U. Leicester), J.P. Osborne (U. Leicester)
and M.H. Siegel report on behalf of the Swift-XRT team:

We have analysed 6.9 ks of XRT data for GRB 160227A (Siegel et al. GCN
Circ. 19098), from 147 s to 31.1 ks after the  BAT trigger. The data
comprise 691 s in Windowed Timing (WT) mode (the first 3 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. 19104).

The late-time light curve (from T0+5.9 ks) can be modelled with a
power-law decay with a decay index of alpha=0.41 (+0.11, -0.10).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.79 (+/-0.03). The
best-fitting absorption column is  7.3 (+0.9, -0.8) x 10^20 cm^-2, in
excess of the Galactic value of 4.1 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.76 (+/-0.10) and a
best-fitting absorption column of 6.6 (+2.8, -2.5) x 10^20 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 3.8 x 10^-11 (4.2 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      6.6 (+2.8, -2.5) x 10^20 cm^-2
Galactic foreground: 4.1 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:      1.76 (+/-0.10)

If the light curve continues to decay with a power-law decay index of
0.41, the count rate at T+24 hours will be 0.15 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.7 x
10^-12 (6.3 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/00676423.

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


GRB_name: GRB160227A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19106
SUBJECT: GRB 160227A, Swift-BAT refined analysis
DATE:    16/02/28 17:12:21 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@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. H. Siegel (PSU),
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 160227A (trigger #676423)
(Siegel et al., GCN Circ. 19098).  The BAT ground-calculated position is
RA, Dec = 195.034, 78.672 deg which is
  RA(J2000)  =  13h 00m 08.1s
  Dec(J2000) = +78d 40' 19.9"
with an uncertainty of 2.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 50%.

The mask-weighted light curve shows a multi-peaked structure that starts
at ~ T0-100 s and ends at ~ T0+270 s. There are roughly four pulses with peaks
at ~ T0-100 s, ~ T0-20 s, ~ T0+100 s, and ~ T0+200 s, respectively.
T90 (15-350 keV) is 316.5 +- 75.4 sec (estimated error including systematics).

The time-averaged spectrum from T-99.8 to T+236.2 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 0.75 +- 0.51,
and Epeak of 65.8 +- 16.4 keV (chi squared 40.42 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 3.1 +- 0.2 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+198.62 sec in the 15-150 keV band is
0.6 +- 0.1 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.65 +- 0.10 (chi squared 51.62 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/676423/BA/


GRB_name: GRB160228A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19107
SUBJECT: GRB 160228A: Swift detection of a burst
DATE:    16/02/28 17:46:31 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

D. Malesani (DARK/NBI), S. D. Barthelmy (GSFC), D. N. Burrows (PSU),
N. P. M. Kuin (UCL-MSSL), A. Y. Lien (GSFC/UMBC),
L. M. McCauley (PSU), D. M. Palmer (LANL), T. G. R. Roegiers (PSU) and
B. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift Team:

At 17:34:32 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160228A (trigger=676595).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 107.322, +26.956 which is 
   RA(J2000)  =  07h 09m 17s
   Dec(J2000) = +26d 57' 23"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows several separated peaks
with a total duration of about 30 sec.  The peak count rate
was ~4200 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 17:35:45.5 UT, 73.1 seconds after
the BAT trigger. Using promptly downlinked data we find a bright, fading,
uncatalogued X-ray source located at RA, Dec 107.31671, 26.93103 which
is equivalent to:
   RA(J2000)  = 07h 09m 16.01s
   Dec(J2000) = +26d 55' 51.7"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 91 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 9.03
x 10^20 cm^-2 (Willingale et al. 2013). 

The initial flux in the 2.5 s image was 1.37e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of nominal 150.000 seconds with the White
filter starting 83 seconds after the BAT trigger. No credible afterglow
candidate has been found in the initial data products. Data from the 2.7'x2.7'
sub-image are not available at this time. 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 0.06. 

Burst Advocate for this burst is D. Malesani (malesani AT dark-cosmology.dk). 
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: GRB160228A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19108
SUBJECT: GRB 160228A: Prompt enhanced Swift-XRT position
DATE:    16/02/28 18:05:53 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 160228A, we find an
enhanced XRT position of the afterglow: RA, Dec: 107.3162, 26.9317
which is equivalent to:
   RA (J2000)  = 07 09 15.90
   Dec (J2000) = +26 55 54.0
with an uncertainty of 2.1 arcseconds (radius, 90% confidence).
Analysis of the promptly available data is online at
http://www.swift.ac.uk/sper/676595.

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: GRB160227A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19109
SUBJECT: GRB 160227A: NOT redshift
DATE:    16/02/28 18:34:30 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

D. Xu (NAOC/CAS), J. P. U. Fynbo, D. Malesani (DARK/NBI), A. de Ugarte 
Postigo (IAA-CSIC, DARK/NBI), T. Petrushevska (Stockholm U.), P. M. 
Sorensen, J. Saario, J. Telting (NOT) report on behalf of a larger 
collaboration:

We observed the field of GRB 160227A (Siegel et al., GCN 19098) using 
the 2.56m Nordic Optical Telescope (NOT) equipped with the ALFOSC 
camera. Observations started at 20:19:12 UT on 2016-02-27 (i.e., 0.784 
hr post-burst) and 2x120s R-band frames were obtained, followed by 
2x1800s+1x1200s spectroscopy (i.e., at a median time of ~1.87 hr 
post-burst) covering 3200A - 9000A, all in a seeing of ~2.0 arcsec.

The previously reported optical afterglow (e.g., Siegel et al., GCN 
19098; Gorbovskoy et al., GCN 19099) is clearly detected in our stacked 
R-band image, with R~19.3 mag calibrated with nearby USNO B1 stars.

Preliminary analysis of the spectrum shows a clear trough at the blue 
end of the spectral continuum, indicating Ly-alpha absorption from H I. 
We also detect several narrow absorption features, though at low 
signal-to-noise, which we interpret as due to, e.g., C II, Si II, O I, C 
II, Fe II, all consistent with a redshift of z = 2.38.


GRB_name: GRB160228A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19110
SUBJECT: GRB 160228A: Enhanced Swift-XRT position
DATE:    16/02/28 20:07:17 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 732 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 160228A, 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 = 107.31636, +26.93173 which is equivalent
to:

RA (J2000): 07h 09m 15.93s
Dec (J2000): +26d 55' 54.2"

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: GRB160227B
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19111
SUBJECT: GRB 160227B: Fermi GBM detection
DATE:    16/02/28 20:58:28 GMT
FROM:    Matthew Stanbro at UAH/Fermi  <mcs0001@uah.edu>

Matthew Stanbro (UAH) and C. Meegan (UAH)
reports on behalf of the Fermi GBM Team:

"At 19:57:06.33 UT on 27 February 2016, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 160227B (trigger 478295830 / 160227831).

The on-ground calculated location, using the GBM trigger
data, is RA = 123.4, DEC = -48.3, with an uncertainty
of 1.3 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 54
degrees.

The GBM light curve consists of 2 episodes
with a duration (T90) of about 8 s (50-300 keV).
The time-averaged spectrum from T0+0.14 s to T0+8.34 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.25 +/- 0.04 and
the cutoff energy, parameterized as Epeak, is 544 +/- 19 keV

The event fluence (10-1000 keV) in this time interval is
(1.86 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.73 s in the 10-1000 keV band
is 10.27 +/- 0.27 ph/s/cm^2.

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


GRB_name: GRB160228A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19112
SUBJECT: GRB 160228A: optical observations
DATE:    16/02/28 21:04:19 GMT
FROM:    Klaas Wiersema at U Leicester  <kw113@leicester.ac.uk>

K. Wiersema (University of Leicester) reports on behalf of the Oadby 
Transients Team:

We observed the field of GRB 160228A (Malesani et al. GCN 19107) using the
0.5m telescope at the observatory of the University of Leicester, at Oadby (UK).
In a series of V band exposures, starting at 19:52 UT on 28 February 2016 (~2.3 hours
after burst), we find no source in or near the XRT error circle (Beardmore et al. 
GCN 19110) to a limit of V<19.5 mag. 


GRB_name: GRB160228A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19113
SUBJECT: GRB 160228A: Swift-BAT refined analysis
DATE:    16/02/29 04:53:26 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),
D. Malesani (DARK/NBI), 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 160228A (trigger #676595)
(Malesani et al., GCN Circ. 19107).  The BAT ground-calculated position is
RA, Dec = 107.311, 26.946 deg which is
  RA(J2000)  =  07h 09m 14.6s
  Dec(J2000) = +26d 56' 45.3"
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 81%.

The mask-weighted light curve shows a short spike from ~T0 to ~T+3 s, followed
by an extended emission till ~T+120 s. This structure is similar to those short
GRBs with extended emission (e.g., Norris et al. 2006). T90 (15-350 keV) is
98.36 +- 23.35 sec (estimated error including systematics).

The time-averaged spectrum from T-0.01 to T+116.104 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.31 +- 0.11.  The fluence in the 15-150 keV band is (2.0 +- 0.1) x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T-0.01 sec in the 15-150 keV band
is 1.2 +- 0.1 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

Moreover, spectral analyses for the short pulse and extended emission intervals
show that the short pulse is harder than the extended emission. Both the
short-pulse spectrum (T0-0.008 to T0+3.188 s) and the extended-emission spectrum
(T0+3.188 to T0+116.104 s) are best fit by the simple power-law model,
with the power-law index of (0.88 +/- 0.17) and (1.35 +/- 0.12), respectively.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/676595/BA/


GRB_name: GRB160228A
Detection_method: correction
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19114
SUBJECT: GRB 160228A: GROND Afterglow Candidate
DATE:    16/02/29 05:47:40 GMT
FROM:    Corentin Delvaux at MPE  <delvaux@mpe.mpg.de>

C. Delvaux, T. Schweyer (both MPE Garching), D. A. Kann (TLS Tautenburg),
and J. Greiner (MPE Garching) report on behalf of the GROND team:

We observed the field of GRB 160228A (Swift trigger 676595; Malesani et
al., GCN #19107) simultaneously in g'r'i'z'JHK with GROND (Greiner et al.
2008, PASP 120, 405) mounted at the 2.2m MPG telescope at the ESO La Silla
Observatory (Chile).

Observations started at 00:02 UT on 2016-02-29, 6.4h after the GRB
trigger. They were performed at an average seeing of 1.2" and at an
average airmass of 1.9.

We detect a single source at the edge of the Swift-XRT error circle
reported by Beardmore et al. (GCN #19110) at

RA (J2000) = 07h09m15.82s
Dec. (J2000) = +26d55'53.8"

with an uncertainty of 0.2" in each coordinate.

Based on 132 min of exposure in g'r'i'z' and 110 min in JHK, at a mid-time
of 01:46 UT, we derive the following preliminary magnitudes and upper
limits (in AB system):

g' = 24.4 +/- 0.1 mag,
r' = 24.4 +/- 0.1 mag,
i' = 23.8 +/- 0.2 mag,
z' = 24.1 +/- 0.3 mag,
J > 22.3 mag,
H > 21.6 mag, and
K > 19.4 mag.

We note the presence of a very close-by (separation < 2") extended bluish
object, lying outside the Swift-XRT error circle, which could be the host
galaxy of the candidate. Another host could be a larger, brighter galaxy
lying at the north of the Swift-XRT error circle (separation ~ 6.6").

We found no evidence of fading of the candidate. Therefore, we cannot
affirm the detected source is the optical afterglow.

Given detections and upper limits are calibrated against GROND zeropoints
as well as 2MASS field stars. No correction for the expected Galactic
foreground extinction corresponding to a reddening of E_(B-V)=0.056 mag in
the direction of the burst (Schlafly & Finkbeiner 2011) has been applied.


GRB_name: GRB160227A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19115
SUBJECT: GRB 160227A: AROMA-N Optical Observation
DATE:    16/02/29 13:07:42 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto@phys.aoyama.ac.jp>

Y. Kitaoka, T. Sakamoto, A. Yoshida (AGU)

We observed the field of GRB 160227A detected by Swift (trigger #676423; 
Siegel et al., GCN Circ. 19098) with the 12-inch AGU Robotic Optical 
Monitor for Astrophysical object - Narrow (AROMA-N) located at 
the Sagamihara campus of Aoyama Gakuin University.  

10 images of 60 sec exposures and 5 images of 180 sec exposures 
were taken in the R filter starting from February 27 19:36:28 (UT) 
about 260 seconds after the trigger and stopped on February 27 20:02:05 (UT).  
Because the target was a low elevation (44.4 deg at the start time) and 
the telescope was slightly out of focus, the quality of the obtained images 
was not ideal.  We do not detect the optical afterglow both in the individual 
images and the stacked image.  The estimated five sigma upper limit of 
the combined image (total exposure of 1500 sec) is ~16.4 mag using 
the USNO-B1 catalog.


GRB_name: GRB160227A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19116
SUBJECT: GRB 160227A: MASTER prompt OT Detection and LC 
DATE:    16/02/29 17:15:15 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V.Krushinski, I.Zalozhnich, A. Popov
Ural State University, Kourovka

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

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

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

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

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


Five telescopes of  MASTER Net of   robotic telescope   participated in 
the observation of the GRB 160227A. Two telescopes  detected 
prompt  optical emission. We discovery very strong OT variations with time 
~100 sec correlated with gamma ray flux (Sakamoto et al., 19106).

MASTER-Ural  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in Ural was pointed to the  GRB160227A 30 sec after notice time 
and 115 sec after trigger time at 2016-02-27 19:34:03 UT. On our first 
(20s exposure)  set we  found 1 optical transient within SWIFT error-box 
(Siegel et al GCN 19098; Gorbovskoy et al GCN 19099) at a position:
RA   12h 59m 14.13s
Dec +78d 40m 44.2s
With magnitude automatical magnitude ~ 17.3
We definetly see OT  at a number of single and coadd images. OT was 
observed during ~ 1 hours. We see OT decay from 17.0 to 19.1 mag in the 
time interval from 115 to 2647 sec atger the trigger.
The 5-sigma upper limit has been about 17.5 mag on first single image and 
up to 19.5 mag at on coadd images in later time.

MASTER-Kislovodsk  robotic telescope (MASTER-Net: 
http://observ.pereplet.ru) 
located in Kislovodsk was pointed to the  GRB160227A  (Siegel et al GCN 
19098) 52 sec after notice time and 137 sec after trigger time at 
2016-02-27 19:34:25 UT. On our first (30s exposure)  set we  marginaly see 
optical transient (Siegel et al GCN 19098, Gorbovskoy et al GCN 19099) 
within SWIFT error-box.  OT also definetly seen at a number of coadd 
images. OT was observed for about 4 hours. We see OT decay from 18.1 to ~ 
20.5 mag in the time interval from 152 to 12900 sec atger the trigger.
The 5-sigma upper limit has been about 17.5 mag on first single image and 
up to 21.0 mag at on coadd images in later time.


MASTER-IAC  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in IAC was pointed to the  GRB160227A 49 sec after notice time and 
137 sec after trigger time at 2016-02-27 19:34:25 UT. On our first (30s 
exposure)  set we haven't found optical transient  within SWIFT error-box. 
The observations started on evening sky (Sun altitude ~ -6 deg). 
Therefore, the first exposure upper limit is very low.  We definetly see 
OT  at a number of coadd images, starting ~ 1 hour after the trigger. OT 
was observed for about 2 hours. We see OT decay from 19.0 to 20.0 mag in 
the time interval from 3400 to 9200 sec atger the trigger.
The 5-sigma upper limit has been about 14.5 mag (due to bright evening sky 
) on first single image and up to 21.0 mag at on coadd images in later 
time.


MASTER-Tunka  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in Astrophysical Center Tunka  was pointed to the  GRB160227A 17 
sec after notice time and 103 sec after trigger time at 2016-02-27 19:33:51 UT. On our first 
(20s exposure)  set we haven't found optical transient  within SWIFT 
error-box. The observations made on not very well weather condition and 
was finished 10 after GRB, due to snow coming.
The 5-sigma upper limit has been about 15.3 mag on first single image.


MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in Blagoveschensk was pointed to the  GRB160227A  8 sec after 
notice time and 93 sec after trigger time at 2016-02-27 19:33:41 UT. On 
our first (20s exposure)  set we haven't found optical transient  within 
SWIFT error-box.
The 5-sigma upper limit has been about 16.0 mag on first single image.


Out preliminary photometry results available at table 1
Light curve available here: http://master.sai.msu.ru/static/grb160227.png


Table 1.

T0-Tmig Expt.   Mag          Site            Coadd
-------|-------|------|---------------------|------
125     20      17.0     MASTER Ural
152     30      18.1     MASTER Kislovodsk
174     30      18.5     MASTER Ural
207     120     17.8     MASTER Kislovodsk     3
231     40      17.7     MASTER Ural
299     50      18.9     MASTER Ural
383     70      19.6     MASTER Ural
485     90      17.9     MASTER Ural
607     110     18.0     MASTER Ural
621     550     18.7     MASTER Kislovodsk     4
757     140     18.7     MASTER Ural
935     170     18.2     MASTER Ural
1133    180     19.1     MASTER Ural
1349    180     19.0     MASTER Ural
1566    180     18.9     MASTER Ural
1765    1080    18.9     MASTER Kislovodsk     6
1781    180     19.1     MASTER Ural
1998    180     19.1     MASTER Ural
2647    900     19.1     MASTER Ural           5
2789    360     19.7     MASTER Kislovodsk     2
3423    540     19.0     MASTER IAC            3
4261    900     19.2     MASTER IAC            5
4527    900     19.4     MASTER Kislovodsk     5
5966    1080    19.5     MASTER Kislovodsk     6
6401    1800    20.0     MASTER IAC           10
7771    3600    19.9     MASTER IAC           20
9196    1800    19.8     MASTER IAC           10
10608   1620    20.9     MASTER Kislovodsk     9
12824   1800    20.3     MASTER Kislovodsk    10


The message may be cited.


GRB_name: GRB160228A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19117
SUBJECT: GRB 160228A: Swift-XRT refined Analysis
DATE:    16/02/29 17:46:02 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), A.P. Beardmore (U.
Leicester), P.A. Evans (U. Leicester), S.L. Gibson (U. Leicester), A.
Maselli  (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB),
T.G.R. Roegiers (PSU) and D. Malesani report on behalf of the Swift-XRT
team:

We have analysed 5.9 ks of XRT data for GRB 160228A (Malesani et al.
GCN Circ. 19107), from 63 s to 40.4 ks after the  BAT trigger. The data
comprise 129 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 Beardmore
et al. (GCN Circ. 19108).

The light curve can be modelled with an initial power-law decay with an
index of alpha=1.01 (+0.26, -0.32), followed by a break at T+125 s to
an alpha of 2.94 (+0.16, -0.14).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.22 (+0.18, -0.16). The
best-fitting absorption column is  2.6 (+1.8, -1.3) x 10^21 cm^-2, in
excess of the Galactic value of 9.0 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.63 (+0.30, -0.28)
and a best-fitting absorption column of 1.8 (+1.4, -0.9) x 10^21 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 4.4 x 10^-11 (5.2 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      1.8 (+1.4, -0.9) x 10^21 cm^-2
Galactic foreground: 9.0 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:      1.63 (+0.30, -0.28)

If the light curve continues to decay with a power-law decay index of
2.94, the count rate at T+24 hours will be 7.1 x 10^-8 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.1 x
10^-18 (3.7 x 10^-18) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00676595.

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


GRB_name: GRB160228A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19118
SUBJECT: GRB 160228A: MASTER-Amur prompt observations 
DATE:    16/02/29 18:04:58 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

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

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

V.Krushinski, I.Zalozhnich, A. Popov
Ural State University, Kourovka

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

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

MASTER-Amur  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in Blagoveschensk was pointed to the  GRB160228A 20 sec after 
notice time and 40 sec after trigger time at 2016-02-28 17:35:12 UT. On 
our first (10s exposure)  set we haven't found optical transient  within 
SWIFT error-box (Malesani et al., GCN 19107) and at GROND OT 
position (Delvaux et al., GCN 19114).
The 5-sigma upper limit has been about 15.1 mag (unfilterd).

We have 3 images during extended emission (Stamatikos et al., GCN 19113) 
with limit 15.2 .

The message may be cited.


GRB_name: GRB160228A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19119
SUBJECT: GRB 160228A: RATIR Optical and NIR Observations
DATE:    16/02/29 18:20:16 GMT
FROM:    Nat Butler at UC berkeley  <natxbutler@gmail.com>

Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William
H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier
Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (GSFC/STScI),
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 160228A (Malesani et al., GCN Circular 19107)
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 2016/02 29.12 to 2016/02 29.38 UTC
(9.23 to 15.50 hours after the BAT trigger), obtaining a total of 4.27
hours exposure in the r and i bands and 1.79 hours exposure in the Z, Y, J,
and H bands.

For a source within the Swift-XRT error circle, in comparison with the
USNO-B1 and 2MASS catalogs, we obtain the following 3-sigma upper limits:

  r > 24.46
  i > 24.39
  Z > 23.21
  Y > 22.76
  J > 22.43
  H > 22.10

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

We do not detect the candidate afterglow seen by Delvaux et al. (GCN Circ
19114) with GROND.  Our upper-limits in rZJH are above their detections.
However, there is weak evidence for fading in i, since GROND detected i =
23.8 Â± 0.2 at about 7.5 hours and we obtain i > 24.4 at 12.4 hours.

We see suggestions of the "extended bluish objectâ€ mentioned by Delvaux et
al. in our r-band image. We also clearly detect the "larger, brighter
galaxyâ€ at 07:09:15.89 +26:55:59.3 (Â±0.5â€) with:

  r = 22.64 Â± 0.07
  i = 22.17 Â± 0.05
  Z = 22.07 Â± 0.13
  Y = 21.69 Â± 0.14
  J = 21.60 Â± 0.17
  H = 21.64 Â± 0.24

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


GRB_name: GRB160228A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19120
SUBJECT: GRB 160228A: Mondy optcial observations
DATE:    16/02/29 19:42:16 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 160228A (Malesani et al., GCN 19107) 
with AZT-33IK telescope of Sayan observatory (Mondy)  starting on Feb.28 
(UT) 18:31:31. Within enhanced XRT position (Beardmore et al., GCN 
19110) we do not detect any optical object. In particular  we do not 
detect candidate of optical afterglow (Delvaux et al., GCN 19114). We 
barely detect extended bluish object mentioned in (Delvaux et al., GCN 
19114). Preliminary photometry  of  a combined image is following


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

2016-02-28  18:31:31  0.06044  R       60*60  22.2

Photometry is base on nearby USNO-B1.0 stars
USNO-B.1_id     R2
1169-0155723    18.59
1169-0155657    19.12
1169-0155662    18.92
1168-0146568    18.65
1169-0155709    19.49


GRB_name: GRB160228A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19121
SUBJECT: GRB160228A: Further analyses on spectral lag and extended emission
DATE:    16/02/29 20:21:35 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

J. P. Norris (BSU), S. D. Barthelmy (GSFC), A. Y. Lien (GSFC/UMBC),
N. Gehrels (GSFC), D. Malesani (DARK/NBI), T. Sakamoto (AGU),
and E. Troja (GSFC/UMCP) report:

We report on the spectral lag analysis of the initial pulse and extended
emission measurements of GRB 160228A (Malesani et al., GCN Circ. 19107).

Using a 32-ms binned light curve (which is the shortest time bin
possible for the lag analysis in this case), the lag of the initial pulse
(~T0 to ~T0+2 s) for the 100-350 keV to 25-50 keV bands is estimated
as 75 (+100/-60) ms (with 1-sigma error).

Despite the large error bars, the lag is inconsistent with zero, and thus
the lag of the initial pulse is much more consistent with those from a long
GRBs rather than short bursts (e.g., Norris et al. 2006).

Moreover, further analysis of the initial pulse intensity shows that it is
only a factor of several more intense than the extended emission in
both the 1-s binned and 32-ms binned light curves, which is much less
prominent than the usual short GRBs with extended emission (e.g.,
Norris et al. 2006).


GRB_name: GRB160227A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19122
SUBJECT: GRB 160227A: Swift/UVOT Detection
DATE:    16/02/29 21:48:36 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <siegel@swift.psu.edu>

M. H. Siegel (PSU) reports on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 160227A
161 s after the BAT trigger (Siegel et al., GCN Circ. 19098).
A source consistent with the XRT position
(Osborne et al. GCN Circ. 19104)
is detected in the initial UVOT exposures but had faded away
in later exposures.

The preliminary UVOT position is:
   RA  (J2000) =  12:59:13.80 = 194.80750 (deg.)
   Dec (J2000) = +78:40:45.1  =  78.67920 (deg.)
with an estimated uncertainty of 0.46 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)         161          311          147         19.34 +/- 0.10
white              600         2418          341         19.80 +/- 0.13 
white             6755         8196          201        >20.82
v                  650         7366          400         19.40 +/- 0.25
b                  575         2393          194         19.71 +/- 0.35
b                 6550         8186          393        >20.10
u (fc)             319          569          245         19.44 +/- 0.20
u                  724         2368          174        >19.22
w1                 699         7776          540        >20.5
m2                1082         7570          432        >21.1
w2                1206         7161          294        >20.7

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: GRB160228A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19123
SUBJECT: GRB 160228A: Swift/UVOT Upper Limits
DATE:    16/02/29 22:50:24 GMT
FROM:    Frank Marshall at GSFC  <femarsha@khamseen.gsfc.nasa.gov>

F. E. Marshall (NASA/GSFC) and D. Malesani (DARK/NBI)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 160228A
83 s after the BAT trigger (Malesani et al., GCN Circ. 19107).
No optical afterglow consistent with the XRT position
(Beardmore et al. GCN Circ. 19110) or the
position of the GROND optical afterglow candidate
(Delvaux et al. GCN Circ. 19114)
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) exposures and subsequent exposures are:

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

white_FC            83          233          147         >20.2
u_FC               296          546          246         >19.5
white               83        10111          342         >20.5
v                  625         5975          236         >19.0
b                  551         6695          138         >19.8
u                  296         6589          462         >20.2
w1                 675         6385          235         >19.8
m2                 650         6179          236         >19.9
w2                 601         5770          235         >19.8

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.06 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB160227A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19124
SUBJECT: GRB 160227A: McDonald 0.8m Detection
DATE:    16/03/01 01:56:44 GMT
FROM:    Myungshin Im at Seoul Nat U  <mim@astro.snu.ac.kr>

Myungshin Im, Changsu Choi, Gu Lim (CEOU/SNU),
Soomin Jeong (SKKU/IAA-CSIC) on behalf of a larger collaboration

We observed the field of GRB 160227A (Palmer et al. GCN19098) using the
0.8m telescope at the McDonald Observatory. The observation started at
2016-02-28 03:03:38 UT, or about
7.5 hours after the BAT alert.
We identify the afterglow at the location of the UVOT detection,
and our preliminary analysis shows the afterglow
at R ~ 20.8 +- 0.15 mag in a stacked image of 21 x 3 min frames.
The mid-point of the observation is 2016-02-28 03:47.
The photometry is calibrated against a star at RA=194.74877
and Dec=78.68984 (J2000) with R=15.72, taken from APASS
catalog.
A second epoch data was taken at about 6 hours later, and the
analysis of the data is ongoing.


GRB_name: GRB160227A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19125
SUBJECT: GRB 160227A: LOAO 1.0m optical detection
DATE:    16/03/01 09:07:13 GMT
FROM:    Soomin Jeong at IAA-CSIC  <sjeong@iaa.es>

Soomin Jeong (SKKU/IAA-CSIC), Myungshin Im (SNU), Yuji Urata (NCU), Il H. Park (SKKU) on behalf of a larger collaboration:

We observed the field of GRB 160227A (Siegel, et al., GCN 19098) with the 1m telescope of Mt. Lemmon Optical Astronomy Observatory (LOAO) in Arizona. 
The series of images are taken in R- & B-filter starting on Feb. 28 05:11:27 UT (~ 9.7 hr post burst). 
The optical counterpart is clearly detected in a median combined image of R at the previously reported optical afterglow position 
(e.g., Siegel et al., GCN 19098; Gorbovskoy et al., GCN 19099; Mazaeva et al., GCN19102). We confirmed marginal detection of OT in a median combined B. 
The observed magnitudes are as following:
Mid Time(hr)     Exposure(s)       Filter       Magnitude
â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”
10.19         12x300            R          21.16 +/- 0.14
10.15          4x300             B           22.19 +/- 0.41
â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”
The fields are calibrated to the near by star at RA=194.74877, Dec=78.68984 (R2=15.84, USNO-B1.0).  


GRB_name: GRB160303A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19126
SUBJECT: GRB 160303A: Swift detection of a burst, possibly short
DATE:    16/03/03 11:14:26 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

A. P. Beardmore (U Leicester), D. N. Burrows (PSU),
P.A. Evans (U Leicester), L. M. McCauley (PSU),
K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of
the Swift Team:

At 10:54:42 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160303A (trigger=677495).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 168.681, +22.742 which is 
   RA(J2000) = 11h 14m 44s
   Dec(J2000) = +22d 44' 33"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a single peak
structure with a duration of about 0.5 s sec.  There is some suggestion
of additional peaks at T-1 and T+5.  The peak count rate
was ~6000 counts/sec (15-350 keV), at ~0.1 sec after the trigger. 

The XRT began observing the field at 10:56:26.1 UT, 104.1 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 168.7005,
22.7424 which is equivalent to:
   RA(J2000)  = 11h 14m 48.11s
   Dec(J2000) = +22d 44' 32.5"
with an uncertainty of 2.2 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. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 1.07
x 10^20 cm^-2 (Willingale et al. 2013). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 108 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
0.02. 

Burst Advocate for this burst is A. P. Beardmore (apb 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: GRB160303A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19127
SUBJECT: GRB 160303A: ISON-NM early optical early limits
DATE:    16/03/03 12:10:37 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

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

We observed the field of the Swift   GRB 160303A (Beardmore et al., GCN 
19126) with 0.4-m telescope of ISON-NM observatory starting on Mar., 03 
(UT) 10:56:02, i.e. ~80 seconds after burst trigger. We obtained 30 
unfiltered images of 30 s exposure. We do not detect any source within 
XRT error circle (Beardmore et al., GCN 19126)  both in the first image 
and in a combined image:

UT start   t-T0         Exp.      Filter  UL (3sigma)
          (mid.,days)    (s)
10:56:02  0.00110        1*30    Clear   19.8
10:56:02  0.00971       30*30    Clear   21.7

The photometry is based on nearby USNO-B1.0 stars


GRB_name: GRB160303A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19128
SUBJECT: GRB 160303A: MITSuME Okayama upper limits
DATE:    16/03/03 12:14:30 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 160303A (Beardmore et al., GCNC 19126)
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 2016-03-03 10:57:10 UT (~2.5 min after
the burst). We did not find any new point source within the XRT
circle (Beardmore et al., GCNC 19126) in all the three bands.

Three sigma upper limits of the OT are listed below.
We used SDSS-DR8 catalog for flux calibration.

#T0+[day]  MID-UT    T-EXP[sec]   g'    Rc     Ic
-----------------------------------------------------
0.00532    11:02:21     540.0   >18.5  >18.6  >18.0
0.01940    11:22:38    2520.0   >19.5  >19.6  >19.0
-----------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]


GRB_name: GRB160303A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19129
SUBJECT: GRB 160303A: LCOGT-FTN optical observations
DATE:    16/03/03 12:20:57 GMT
FROM:    Simone Dichiara at Ferrara U/Italy  <dichiara@fe.infn.it>

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

The 2-m LCOGT Faulkes Telescope North began observing Swift GRB 160303A
(Beardmore et al., GCN 19126) on March 03, 11:18 UT (23 minutes after the
burst trigger) with i' filter. Inside the XRT error circle we find no
source down to i'> 21.2 mag in a 5x120s exposure (at 28.7 min, mid time),
as calibrated against nearby SDSS stars, in agreement with the limits
reported by Elenin et al. (GCN 19127).


GRB_name: GRB160303A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19130
SUBJECT: GRB 160303A: MITSuME Akeno optical upper limits
DATE:    16/03/03 12:24:54 GMT
FROM:    Taketoshi Yoshii at Tokyo Tech  <yoshii.t.ac@m.titech.ac.jp>

Y.Tachibana, T.Fujiwara, T. Yoshii, Y. Saito, H. Ohuchi, Y. Yano, S. Kurita, 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 160303A (Beardmore et al., GCN Circular #19126) 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 2016-03-03 10:55:44 UT (~1 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+[hour]    MID-UT     T-EXP[sec]      g'         Rc          Ic
----------------------------------------------------------------------------
  0.43        11:20:38         2610       >20.3     >20.4    >19.6
----------------------------------------------------------------------------
T0+ : Elapsed time after the burst 
T-EXP: Total Exposure time 
We used GSC2.3 catalog for flux calibration.


GRB_name: GRB160303A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19131
SUBJECT: GRB 160303A: RATIR Optical and NIR Afterglow Detection
DATE:    16/03/03 13:07:10 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 (STScI), J. Xavier
Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (GSFC/STScI),
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 160303A (Beardmore, et al., GCN 19126) 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 2016/03 3.46 to 2016/03 3.52 UTC (1.8
minutes to 1.50 hours after the BAT trigger), obtaining a total of 1.02
hours exposure in the r and i bands and 0.44 hours exposure in the Z, Y, J,
and H bands.

We detect an uncatalogued source within the Swift-XRT error circle, in
comparison with the SDSS DR9 and 2MASS catalogs, we obtain the following
detections and upper limits (3-sigma):

  r = 22.95 +/- 0.31
  i = 22.65 +/- 0.23
  Z > 21.98
  Y = 21.83 +/- 0.36
  J > 21.30
  H > 21.01

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 =
11:14:48.12, +22:44:32.6 (J2000, +/-0.5").

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


GRB_name: GRB160303A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19132
SUBJECT: GRB 160303A: Enhanced Swift-XRT position
DATE:    16/03/03 14:09:07 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 2035 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 160303A, 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 = 168.70075, +22.74213 which is equivalent
to:

RA (J2000): 11h 14m 48.18s
Dec (J2000): +22d 44' 31.7"

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: GRB160303A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19133
SUBJECT: GRB 160303A: RAPTOR Observations During Gamma-Ray Emitting Interval
DATE:    16/03/03 19:05:45 GMT
FROM:    James Wren at LANL  <jwren@lanl.gov>

J. Wren, W.T. Vestrand, P. Wozniak, and H. Davis
of Los Alamos National Laboratory report:

The RAPTOR network of robotic optical telescopes made observations of Swift
trigger 677495 (Beardmore, et al., GCN 19126).  The burst location was within
the field of our wide-field monitor located in Maui, HI, which began a 10 s
integration of the location beginning at 10:54:38.19 UT, 3.86 s before the
Swift trigger time and during the gamma-ray emitting interval.  We do not
detect an optical counterpart to a limiting magnitude of 10.5.  Our 3-sigma
limiting magnitudes are based on a comparison of our unfiltered image to the
Tycho-2 V-band catalog.


GRB_name: GRB160303A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19134
SUBJECT: GRB 160303A: Swift/UVOT Detection
DATE:    16/03/03 20:15:46 GMT
FROM:    Sam Emery at MSSL-UCL  <samuel.emery.15@ucl.ac.uk>

S.W.K. Emery (UCL-MSSL) and A. P. Beardmore (U Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 160303A
109 s after the BAT trigger (Beardmore et al., GCN Circ. 19126).
We detect a fading source consistent with the XRT position
(Beardmore et al. GCN Circ. 19126) and the RATIR optical and NIR afterglow
detections (Butler et al. GCN Circ 19131)
in the initial UVOT u filter 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           109         259          147         >21.9
u_FC                   321         571          246          20.75
white                 109          2061        450         >22.5
b                         576          2037        136         >19.9
w1                      700          2161           77         >20.5
m2                     1426        1445           19         >19.5

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: GRB160303A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19136
SUBJECT: GRB 160303A: Optical observations from the NOT
DATE:    16/03/03 23:39:37 GMT
FROM:    Antonio de Ugarte Postigo at IAA-CSIC  <deugarte@iaa.es>

A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), D. Malesani (DARK/NBI),
N.R. Tanvir (U. Leicester), Z. Cano (U. Iceland), M. Messa (Stockholm 
Univ., Oskar Klein Centre), E. Gafton (NOT, Stockholm Univ. and Oskar 
Klein Centre) and I. R. Losada (Nordita and Stockholm Univ.) report on 
behalf of a larger collaboration:

We observed the field of the possibly short GRB 160303A (Beardmore et al., 
GCN 19126) with MOSCA at the 2.5m Nordic Optical Telescope (La Palma, 
Spain). Observations started at 21:32 UT (10.63 hr after the burst). In an 
8x300s r-band exposure we detect a source consistent with the counterpart 
candidate identified by RATIR (Butler et al. GCN 19131), and also seen by 
UVOT (Emery et al. GCN 19134).

Comparing with SDSS field stars we obtain a photometric value of 
r=23.43+/-0.15 (AB). This would imply only a modest (if any) fading 
compared to the RATIR observation. This may be indicative of a significant 
contribution from an underlying host galaxy.

We do note that the coordinates that we measure are slightly offset from 
those given in the RATIR GCN, being our object marginally outside the 
refined XRT error circle(Evans et al., GCN 19132,  
http://www.swift.ac.uk/xrt_positions/00677495/ <http://www.swift.ac.uk/xrt_positions/00677495/>), at the following coordinates 
(J2000, +/- 0.3"):

RA = 11:14:48.06
Dec = +22:44:32.2


GRB_name: GRB160303A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19137
SUBJECT: GRB 160303A: Swift-XRT refined Analysis
DATE:    16/03/03 23:40:56 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

D.N. Burrows (PSU), P.A. Evans (U. Leicester), S.L. Gibson (U.
Leicester), J.P. Osborne (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 A.P. Beardmore report on behalf of the Swift-XRT
team:

We have analysed 7.0 ks of XRT data for GRB 160303A (Beardmore et al.
GCN Circ. 19126), from 87 s to 23.3 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 Evans et al. (GCN Circ.
19132).

The light curve can be modelled with a power-law decay with a decay
index of alpha=2.36 (+0.17, -0.16).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.70 (+0.24, -0.22). The
best-fitting absorption column is  5.2 (+6.7, -4.1) x 10^20 cm^-2,
consistent with the Galactic value of 1.1 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 3.8 x 10^-11 (4.1 x
10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      5.2 (+6.7, -4.1) x 10^20 cm^-2
Galactic foreground: 1.1 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:      1.70 (+0.24, -0.22)

If the light curve continues to decay with a power-law decay index of
2.36, the count rate at T+24 hours will be 6.7 x 10^-7 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.6 x
10^-17 (2.8 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/00677495.

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


GRB_name: GRB160303A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19138
SUBJECT: GRB 160303A iTelescope observation
DATE:    16/03/04 02:26:10 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto@phys.aoyama.ac.jp>

T. Sakamoto, Y. Kitaoka, A. Yoshida (AGU) 

We observed the field of GRB 160303A detected by Swift (trigger #677495;
Beardmore et al., GCN Circ. 19126) with the iTelescope.Net (http://www.itelescope.net) 
T21 (Plane Wave 17" CDK) telescope located at the New Mexico Skies Observatory 
(NM, USA).  

15 images of 60 sec exposures were taken in the R filter starting from March 3 11:19:26 (UT) 
about 25 minutes after the trigger and stopped on March 3 11:38:20 (UT).  
We do not detect the optical afterglow both in the individual images and the stacked image 
at the X-ray and the optical afterglow position (Evans et al., GCN Circ. 19132; 
Butler et al., GCN Circ. 19131).  The estimated five sigma upper limit of the combined 
image (total exposure of 900 sec) is ~18.3 using the USNO-B1 catalog.


GRB_name: GRB160303A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19139
SUBJECT: GRB 160303A SMA observation
DATE:    16/03/04 06:54:27 GMT
FROM:    Yuji Urata at Nat. Central U.  <urata@astro.ncu.edu.tw>

GRB 160303A SMA observation

Y. Urata (NCU), K.Y Huang (NTNU), and G. Petitpas (SMA)

We observed the optical afterglow position of GRB 130303A (Butler et
al., GCN Circ. 19131) using the Sub-Millimeter Array (SMA). The
observation in 230 GHz band was started at March 3 12:47 (UT) about
1.9 hrs after the burst.  Our preliminary analysis shows no
counterpart brighter than 2.4 mJy (3-sigma).


GRB_name: GRB160303A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19140
SUBJECT: GRB 160303A: McDonald 2.1m CQUEAN Detection
DATE:    16/03/04 12:34:56 GMT
FROM:    Soomin Jeong at IAA-CSIC  <sjeong@iaa.es>

Soomin Jeong (SKKU/IAA-CSIC), Myungshin Im, Changsu Choi and Gu Lim (CEOU/SNU) on behalf of a larger collaboration:


We observed the field of GRB160303A (Beardmore et al., GCN 19126) with CQUEAN at the Otto Struve 2.1 m telescope


in McDonald Observatory, Texas. The observation started at 11:44, Mar 03 UT (i.e. 0.83 hr post burst) and the observation 

was conducted in r-, i-, R-, z- band. 



In the median combined image (5 x 120s) of i-band, a possible counterpart is detected near the centre of XRT enhanced 

position (Evans et al., GCN 19132). We noticed that our i-band detection is slightly offset from a previously identified position 

by RATIR (Butler et al., GCN 19131) and found another marginal detection at the RATIR detection, i.e., outskirt of XRT 

enhanced position (Evans et al., GCN 19132).


 
Faint features are barely detected also in an 5 x 120s, r-band exposure, however the detection error is too big to reveal its reality. 

It is in relatively outskirt within XRT enhanced error circle and at the previously reported optical position (Butler et al., GCN 19131; Emery et al., GCN 19134). 

In comparison to other reports, the detection in i-band looks like a fading afterglow (Butler et al., GCN 19131), and the position of

 the possible object in r-band is coincident to the previous optical detection by RATIR (Butler et al., GCN 19131) and NOT (De Ugarte et al., GCN 19136). 

The faint r-band source could be the host galaxy or highly contaminated counterpart from the underlying host. 


The analysis of R- and z-band images is still ongoing. 



T_mid (hr)  Exposure (s)     Filter       Magnitude (AB)


-----------------------------------------------------------------------------------

0.92               5x120               i          22.54 +/- 0.26 

1.13               5x120               r          23.06 +/- 0.41

------------------------------------------------------------------------------------

The fields are calibrated to a nearby star at RA=168.701176, Dec=22.745212 from SDSS. 


GRB_name: GRB160303A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19141
SUBJECT: GRB 160303A: BOAO R-band Detection
DATE:    16/03/04 15:28:40 GMT
FROM:    Myungshin Im at Seoul Nat U  <mim@astro.snu.ac.kr>

Myungshin Im (CEOU/SNU), Hyun-Il Sung (KASI), Yuji Urata (NCU),
Soomin Jeong (SKKU/IAA-CSIC)

We observed the field of GRB 160303A (Beardmore et al. GCN 19126)
using the 1.8m telescope at the Bohyunsan Optical Astronomy Observatory
â€‹ â€‹
(BOAO) in Korea. The observation started at
2016-02-28 13:31:46 UT,
â€‹ â€‹
or about 2.6 hours after the BAT alert.

We clearly identify the afterglow at the location of the RATIR detection
(Butler et al. GCN 19131) with R = 22.75 +- 0.12 mag in a stacked
image of 6 x 5 min frames (Mid-point: 2016-02-28 13:54). Together with the
â€‹ resultâ€‹
 at 10
â€‹ â€‹
hrs after the BAT alert (de Ugarte Postiago et al.
â€‹â€‹
GCN 19136), our photometry unambiguously confirms the fading nature of this
source. Further observation and the analysis of the data are
planned.

We thank the BOAO staffs for their assistance with the observation.


GRB_name: GRB160303A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19142
SUBJECT: GRB 160303A: VLT/FORS2 afterglow obervations
DATE:    16/03/04 15:36:10 GMT
FROM:    Thomas Kruehler at MPE Garching  <kruehler@mpe.mpg.de>

S. Klose, A. Nicuesa Guelbenzu (both TLS Tautenburg),
T. Kruehler (MPE Garching), D. Malesani (DARK/NBI) and J. Greiner
(MPE Garching) report on behalf of a larger collaboration:

We observed the field of GRB 160303A (Swift trigger 677495; Beardmore et
al., GCN #19126) with FORS2 at ESO's Very Large Telescope. Imaging in
the R-band filter started at 05:40:42 UT on 2016-03-04, 18.8 hr after
the GRB trigger.

In a 4x25 s exposure, we clearly detect the candidate counterpart
(Butler et al. GCN#19131, Emery & Beardmore, GCN#19134,
de Ugarte Postigo et al. GCN#19136) at a position consistent with
the one provided by de Ugarte Postigo et al. (GCN#19136). The source
appears point-like in the image which has a stellar PSF with a
FWHM of 0.72".

Calibrating our data against r-band photometry of field stars
from the SDSS catalog, we measure a preliminary AB magnitude of

r = 24.11 +- 0.15

This implies significant fading against the earlier measurements from
Butler et al. (GCN#19131) and de Ugarte Postigo et al. (GCN#19136),
indicating that this source is the GRB afterglow (see also Im et al., 
GCN#19141).

We acknowledge excellent support from ESO Paranal Science Operations,
in particular from Emanuela Pompei and the team at VLT/Antu.

[GCN OPS NOTE(06mar16): Per author's request, the final paragraph was added.]


GRB_name: GRB160303A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19143
SUBJECT: GRB 160303A: Observations from T150 OSN
DATE:    16/03/04 15:46:17 GMT
FROM:    Antonio de Ugarte Postigo at IAA-CSIC  <deugarte@iaa.es>

A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), C.C. Thoene (IAA-CSIC),
V. Casanova (IAA-CSIC) report on behalf of a larger collaboration:

We observed the field of the possibly short GRB 160303A (Beardmore et al., 
GCN 19126) with the 1.5 m OSN telescope (Sierra Nevada Observatory, 
Granada, Spain). Observation consisted of 15x300s exposures in R-band, 
ranging from 01:37-3:00 UT (mean epoch at 15.41 hr after the burst).

In the combined image the GRB afterglow (Butler et al., GCN 19131; Emery 
et al. GCN 19134; de Ugarte Postigo, GCN 19136; Jeong et al. GCN19140; 
Im et al. GCN 19141; Klose et al. GCN 19142) is seen at a magnitude of 
r(AB) = 23.67 +/- 0.27 as compared to SDSS stars.

This seems to indicate confirm the decay as compared with the data of 
RATIR (Butler et al., GCN 19131), NOT (de Ugarte Postigo, GCN 19136) and
CQUEAN (Jeong et al. GCN19140), BOAO (Im et al. GCN 19141) and FORS
(Klose et al. GCN 19142). In any case the possible decay would be shallower
than the typical GRB, with a decay slope of alpha ~ 0.5 (F_nu ~ t^-alpha).


GRB_name: GRB160303A
Detection_method: correction
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19144
SUBJECT: GRB 160303A: GROND Optical Detection
DATE:    16/03/04 16:33:25 GMT
FROM:    Philip Wiseman at MPE/Swift  <wiseman@mpe.mpg.de>

J. Graham, J. Bolmer, P. Wiseman and J. Greiner (all MPE Garching) report on
behalf of the GROND team:

We observed the field of GRB 160303A (Swift trigger 677495; Beardmore et
al., GCN #19126) simultaneously in g'r'i'z'JHK with GROND (Greiner et al.
2008, PASP 120, 405) mounted at the 2.2m MPG telescope at the ESO La Silla
Observatory (Chile)./
/Observations started at 03:27 UT on 2016-03-04, 16.5h after the GRB
trigger. They were performed at an average seeing of 1.3" and at an
average airmass of 1.6./
/We detect a single source at the edge of the Swift-XRT error circle
reported by Evans et al. (GCN #19132) consistent with the optical 
candidate from de Ugarte Postigo et al. (GCN #19136) and Klose et al. 
(GCN #19142)/
/Based on 66 min of exposure in g'r'i'z' and 60 min in JHK, at a mid-time
of 04:54 UT, we derive the following preliminary magnitudes and upper
limits (in AB system):/
/g' = 24.2 +/- 0.1 mag,
r' = 24.0 +/- 0.1 mag,
i' = 23.9 +/- 0.2 mag,
z' = 23.5 +/- 0.3 mag,
J > 21.1 mag,
H > 20.1 mag, and
K > 19.5 mag./
/Given detections and upper limits are calibrated against SDSS
as well as 2MASS field stars. No correction for the expected Galactic
foreground extinction corresponding to a reddening of E_(B-V)=0.014 mag in
the direction of the burst (Schlafly & Finkbeiner 2011) has been applied.

-- 
Philip Wiseman                 wiseman@mpe.mpg.de
Doctoral Student          +49 (0)89 30000-3566
GRB Group                +49 (0)1605 011752

IMPRS Student Representative

Room X5 1.3.09
Max-Planck-Institute fuer extraterrestriche Physik
Giessenbachstrasse 1
85748 Garching, Germany


GRB_name: GRB160303A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19146
SUBJECT: GRB 160303A: Continued RATIR Optical and NIR Observations
DATE:    16/03/04 18:38:31 GMT
FROM:    Eleonora Troja at GSFC  <eleonora.troja@nasa.gov>

Eleonora Troja (GSFC), Nat Butler (ASU), Alan M. Watson (UNAM), 
Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer 
(UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), 
Antonino Cucchiara (GSFC/STScI), 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 160303A (Beardmore, et al., GCN 19126) 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 2016/03 4.12 to 2016/03 4.53 
UTC (16.00 to 25.72 hours after the BAT trigger), obtaining a total of 
5.52 hours exposure in the r and i bands and 2.27 hours exposure in the 
Z, Y, J, and H bands.

The source reported by Butler et al. (GCN 19131) is not detected in our 
images. In comparison with the SDSS DR9 and 2MASS catalogs, we obtain 
the following upper limits (3-sigma):

   r    > 23.77
   i    > 23.88
   Z    > 22.37
   Y    > 21.77
   J    > 21.52
   H    > 21.45

These magnitudes are in the AB system and are not corrected for Galactic 
extinction in the direction of the GRB. Our upper limits are consistent 
with the GROND measurements (Graham et al., GCN 19144) and confirm that 
the source was the afterglow of GRB160303A.

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


GRB_name: GRB160303A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19147
SUBJECT: GRB 160303A: MMT Optical Detection
DATE:    16/03/04 19:45:16 GMT
FROM:    Wen-fai Fong at U of Arizona  <wfong@email.arizona.edu>

W. Fong (University of Arizona) reports on behalf of a larger collaboration:

"We observed the location of the possibly short-duration GRB 160303A
(Beardmore et al., GCN 19126) with MMTCam mounted on the 6.5-m MMT at a
mid-time of 2016 Mar 4.232 UT (18.64 hr post-burst). We obtained 9x200-sec
of r-band observations in 1.0" seeing at a mean airmass of 1.2. We detect
the optical afterglow (Butler et al., GCN 19131) with a magnitude of
r(AB)~23.90 +/- 0.15 (calibrated to SDSS) at a position consistent with the
NOT position (de Ugarte Postigo et al., GCN 19136). Our measured afterglow
brightness is consistent with the VLT value at a similar epoch (Klose et
al., GCN 19142)."


GRB_name: GRB160303A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19148
SUBJECT: GRB 160303A, Swift-BAT refined analysis
DATE:    16/03/04 22:56:56 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

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

Using the data set from T-61 to T+200 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 160303A (trigger #677495)
(Beardmore, et al. GCN Circ. 19126).  The BAT ground-calculated position is
RA, Dec = 168.710, 22.710 deg which is
  RA(J2000)  =  11h 14m 50.3s
  Dec(J2000) = +22d 42' 35.1"
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 96%.

The mask-weighted light curve shows a short spike that start and peaks at ~T0,
and ends at ~T+0.4 s. There is a hint of a weak tail that lasts till ~T+5 s
T90 (15-350 keV) is 5.0 +- 0.8 sec (estimated error including systematics).

Note that for this burst, the auto process generates fairly inconsistent results of the
burst durations (ranging from T90 of ~ 0.4 s to T90 of ~ 18 s) when using light curves
with different time bins and/or different length of data range. This is likely due to the
ambiguous weak-tail feature in the light curve after the short spike.

Thus, we did further checks of the reality of the weak tail by an alternative Bayesian
Block method based on Scargle et al. (2013), and by searching for detections in
images created using different time intervals. We conclude that there is likely no burst
emission after ~T+5 s, because no burst structure is picked out by the alternative
Bayesian Block method afterwards, and also the signal-to-noise ratio is only about
one in images created after ~T+5. The image created using T+1 s to T+5 s gives
a signal-to-noise ratio of ~ 4.

The lag analysis using the 8-ms binned light curve shows a lag of 24 ms +- 24 ms
for the 100-350 keV to 25-50 keV band, which is inconclusive for the burst nature
due to the weakness of the burst.

We therefore decided to report T90 based on results using data till ~T0+200 s,
which gives a T90 of ~ 5 s and is consistent with our checks. However, due to
the relatively low significance of the tail. We report the spectral analyses for
both the total range and the the short spike.

The time-averaged spectrum from T-0.1 to T+5.3 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.01 +- 0.33.  The fluence in the 15-150 keV band is 1.5 +- 0.3 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-0.09 sec in the 15-150 keV band
is 1.0 +- 0.1 ph/cm2/sec.

The spectrum of the short spike from T-0.09 to T+0.40 sec is best fit by a simple
power-law model.  The power law index of the short-spike spectrum is
0.84 +- 0.20.  The fluence in the 15-150 keV band is 8.78 +- 1.1 x 10^-8 erg/cm2.
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/677495/BA/


GRB_name: GRB160303A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19149
SUBJECT: GRB 160303A: 9.8 GHz VLA upper limit
DATE:    16/03/05 00:51:07 GMT
FROM:    Wen-fai Fong at U of Arizona  <wfong@email.arizona.edu>

W. Fong (University of Arizona) reports:

"We observed the field of GRB 160303A (Beardmore et al., GCN 19126) with
the Karl G. Jansky Very Large Array (VLA) beginning on 2016 Mar 4.218 UT
(18.32 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 (Evans et al., GCN 19132) or the optical afterglow
position (Butler et al., GCN 19131; de Ugarte Postigo et al., GCN 19136) to
a 3-sigma limit of 15.2 microJy. We therefore place a 3-sigma limit of 15.2
microJy on the radio afterglow of GRB 160303A at 18.32 hr after the burst.

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


GRB_name: GRB160303A
Detection_method: correction
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19150
SUBJECT: GRB160303A: further GROND observations
DATE:    16/03/05 14:33:55 GMT
FROM:    Jan Bolmer at MPE/Garching  <jan@bolmer.de>

J. Bolmer, J. Greiner (both MPE Garching) and D.A. Kann (TLS Tautenburg) report on
behalf of the GROND team:

We re-observed the field of GRB 160303A (Swift trigger 677495; Beardmore et
al., GCN #19126) simultaneously in g'r'i'z'JHK with GROND (Greiner et al.
2008, PASP 120, 405) mounted at the 2.2m MPG telescope at the ESO La Silla
Observatory (Chile).

Observations started at 03:58 UT on 2016-03-05, 41.1h after the GRB
trigger. They were performed at an average seeing of 1.0" and at an
average airmass of 1.6.

We still detect a faint source at the initially reported position (Graham et al. GCN#19144,
de Ugarte Postigo et al. (GCN #19136)).

Based on 96 min of exposure in g'r'i'z', at a mid-time
of 04:52 UT, we derive the following preliminary magnitudes and upper
limits (in AB system):

g' = 25.2 +/- 0.2 mag,
r' = 25.1 +/- 0.2 mag,
i' > 24.3 mag,
z' > 24.4 mag,

Given detections and upper limits are calibrated against SDSS field stars. 
No correction for the expected Galactic foreground extinction corresponding
to a reddening of E_(B-V)=0.014 mag in the direction of the burst
(Schlafly & Finkbeiner 2011) has been applied.

Combining our GROND measurements with those from 10.63 h after the GRB
(de Ugarte Postigo et al., GCN #19136), we obtain a decay slope of
alpha = - 1.1 +/- 0.2 in the r' band.


GRB_name: GRB160303A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19151
SUBJECT: GRB 160303A: JCMT SCUBA-2 sub-mm observation
DATE:    16/03/05 17:59:00 GMT
FROM:    Ian Smith at Rice U  <ian@spacsun.rice.edu>

I.A. Smith (Rice U.), N.R. Tanvir (U. of Leicester), and Y. Urata (NCU) 
report:

We observed the location of the possibly short GRB 160303A (Beardmore 
et al., GCN Circ. 19126) using the SCUBA-2 sub-millimeter continuum 
camera on the James Clerk Maxwell Telescope.  The observation started 
at 11:56 UT on 2016-03-03, corresponding to 62 minutes after the burst
trigger.  Exposures totaling 2.0 hours were made in good weather
conditions.  No source was detected, with the RMS background noise
being 1.4 mJy/beam at 850 microns and 14.8 mJy/beam at 450 microns.

We thank Callie Matulonis and Iain Coulson for the prompt support 
of these observations that were taken under project M16AP005.


GRB_name: GRB160303A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19152
SUBJECT: GRB 160303A: Continued optical monitoring from NOT
DATE:    16/03/05 20:35:02 GMT
FROM:    Antonio de Ugarte Postigo at IAA-CSIC  <deugarte@iaa.es>

A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), T. Kruehler (MPE Garching)
D. Xu (NAOC/CAS), D. Malesani (DARK/NBI), Z. Cano (U. Iceland),
N.R. Tanvir (U. Leicester),M. Messa (Stockholm Univ., Oskar Klein Centre), 
E. Gafton (NOT, Stockholm Univ. and Oskar Klein Centre) and I. R. Losada 
(Nordita and Stockholm Univ.) report on behalf of a larger collaboration:

We continued the monitoring of GRB 160303A (Beardmore et al., 
GCN 19126) with MOSCA at the 2.5m Nordic Optical Telescope 
(La Palma, Spain).

On a 9x300s  observation with mean epoch 2:10 UT of 5 March 2016 
(37.27 hr after the burst) we detect the afterglow (Butler et al GCN19131) 
at a magnitude of r = 25.2 +/- 0.2, as compared to the SDSS field stars. 
This is consistent with the magnitude reported by GROND (Bolmer et al. 
GCN 19150) at a similar epoch.

Gathering the r-band data from the different GCNs (Butler et al. GCN19131; 
de Ugarte Postigo et al. GCN 19136; Jeong et al. GCN 19140; Im et al. 
GCN 19141; Klose et al. GCN 19142; de Ugarte Postigo et al. GCN 19143; 
Graham et al. GCN 19144; Bolmer et al. GCN 19150) the light curve seems 
to have been flat, or even increasing in brightness during the first 4-8 hrs 
after the burst. After this, the light curve begins a steep decay with 
alpha = 1.23 +/- 0.14 (F_nu ~ t^-alpha). This is not unlike the behaviour of 
other short GRBs, f.ex. GRB 130603B (de Ugarte Postigo et al. 2014 
A&A 563, 62), which was interpreted as being a magnetar powered event.


GRB_name: GRB160303A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19154
SUBJECT: GRB 160303A: X-shooter spectroscopy
DATE:    16/03/06 02:22:25 GMT
FROM:    Antonio de Ugarte Postigo at IAA-CSIC  <deugarte@iaa.es>

A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), D. Malesani (DARK/NBI),
T. Kruehler (MPE Garching), D. Xu (NAOC/CAS), S. Schulze (PUC, MAS), 
J. Hjorth (DARK/NBI), N.R. Tanvir (U. Leicester) report on behalf of a 
larger collaboration:


We observed the afterglow of GRB 160303A (Beardmore et al., 
GCN 19126; Butler et al., GCN 19131) with ESOâ€™s Very Large Telescope  
UT2 equipped with X-shooter (Paranal Observatory, Chile). The spectra 
cover the range from 3000 to 18000 AA. Observations consisted of 4x1200s 
exposures, starting at 06:03 UT of 4 March 2016 (18.8 hr after the GRB 
onset).

The spectrum was obtained when the GRB was at r ~ 24.1 (Klose et al. 
GCN 19142) and hence the S/N is rather low, implying that no absorption 
feature can be identified. In spite of this, a trace can be seen in the 
complete UVB (3000-5600AA) and VIS (5600-10100 AA) spectra. The 
continuum is rather blue, as already seen from multiband photometry 
(Butler et al., GCN 19131; Graham et al., GCN 19144). The detection of the 
trace down to 3000 AA implies a redshift limit of < 2.3 (considering that the 
Lyman break is not within the range).

In spite of the deep spectrum, we have not been able to identify any emission 
feature, which could be indicative of a very faint galaxy and/or a non star 
forming galaxy (which would be expected for a SGRB).

We acknowledge excellent support from the Paranal staff.


GRB_name: GRB160310A
Detection_method: Fermi LAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19158
SUBJECT: GRB 160310A: Fermi-LAT detection
DATE:    16/03/10 10:12:10 GMT
FROM:    Giacomo Vianello at SLAC  <giacomov@slac.stanford.edu>

G.Vianello (Stanford), M. Yassine (CNRS/IN2P3), E.Moretti (MPP Munich)

report on behalf of the Fermi-LAT team:

At 00:22:58.47 on March, 10, 2016 (T0) Fermi-LAT detected high-energy
emission from GRB 160310A, which was also detected by Fermi-GBM
(trigger 479262181 / 160310016).

The best LAT on-ground location is found to be

RA, Dec = 98.78, -7.11 (J2000)

with an error radius of 0.1 deg (90 % containment, statistical error only).

This was 62 deg from the LAT boresight at the time of the trigger, on
the edge of the field of view.

The data from the Fermi-LAT show a significant increase in the event
rate that is spatially and temporally correlated with the trigger with
high significance.

At the time of the trigger Fermi was in normal survey mode. The GRB
was observable by Fermi from T0 to ~T0 + 500 s, and then again from
~T0 + 5200 s and T0 + 7000 s. The highest-energy photon is a 30 GeV
event which is observed 5800 seconds after the GBM trigger.

A Swift ToO has been requested for this burst.

The Fermi-LAT point of contact for this burst is Giacomo Vianello
(giacomov@stanford.edu).

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: GRB160310A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19159
SUBJECT: GRB 160310A: Swift ToO observations
DATE:    16/03/10 11:39:20 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 160310A. 
Automated analysis of the XRT data will be presented online at
http://www.swift.ac.uk/ToO_GRBs/00020602

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: GRB160303A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19160
SUBJECT: GRB 160303A: GTC imaging of possible host galaxy
DATE:    16/03/10 13:38:32 GMT
FROM:    Zach Cano at U of Iceland  <zewcano@gmail.com>

â€‹Z. Cano (U. Iceland), A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), D.
Malesani (DARK/NBI) and C. C. Thoene (IAA-CSIC) report on behalf of a
larger collaboration:

We observed the field of GRB 160303A (Beardmore et al., GCN Circ. 19126)
with the 10.4-m GTC telescope (OSIRIS instrument) on 2016 March 8.15 UT
(+4.7 days) in SDSS filters r and i.  The optical transient associated with
this event (Butler et al., GCN Circ. 19131) is no longer detected.
Instead, we note the presence of a nearby, extended source with an r-band
(AB) magnitude of 25.8 +- 0.3, as calibrated using nearby SDSS stars.

After registering the astrometry of the GTC images against our NOT
afterglow image (de Ugarte Postigo et al., GCN Circ. 19136), we find that
the centroid of the extended object is offset by 1.7'' +- 0.3'' in the
North-East direction.  We note that the radial extent of this object nearly
reaches the position of the previously detected optical transient.  Using
the equations from Bloom, Kulkarni & Djorgovski (2002, AJ, 123, 1111), we
calculate that the chance probability of finding an object with r = 25.8 at
a separation of 1.7'' is 14% -- small, but not negligible.

If the extended object is associated with GRB 160303A, then for a standard
cosmology this angular separation corresponds to 3.2, 5.6, 7.6, 10.5 kpc
for redshifts of z=0.1, 0.2, 0.3, 0.5, respectively.  This offset is
consistent with that measured for short-duration GRBs at z=0.2 (median
offset = 5 kpc for a range of 0.5-75 kpc; Fong, Berger & Fox 2010, ApJ,
708, 9).  Instead, if GRB 160303A is a long-duration GRB, for this offset
to be consistent with those measured for LGRBs (1 kpc, Bloom, Kulkarni &
Djorgovski 2002, AJ, 123, 1111; de Ugarte Postigo et al. 2012, A&A, 548,
11), it would require a redshift of z=0.03.  The luminosity distance at
this redshift implies an absolute magnitude of M_r=-9.8, which is roughly
eight to ten magnitudes fainter than those measured for LGRB host galaxies
in sample studies (Savaglio, Glazebrook & Le Borgne, ApJ, 691, 182;
Kruehler et al. 2015, A&A, 581, 125).  Based on this line of argument, this
observation suggests that GRB 160303A may be a short-duration GRB.

We acknowledge the excellent support given by the GTC staff.


GRB_name: GRB160310A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19161
SUBJECT: GRB 160310A: Fermi GBM observation
DATE:    16/03/10 15:30:33 GMT
FROM:    Kilian Toelge at MPE  <tkili@mpe.mpg.de>

Kilian Toelge (MPE) and Michelle Hui (UAH)
report on behalf of the Fermi GBM Team:

"At 00:22:58.47 UT on 10 March 2016, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 160310A (trigger 479262182 / 160310016),
which was also detected by the LAT
(G.Vianello et al. 2016, GCN 19158)
The GBM on-ground location is consistent with the LAT position.

The angle from the Fermi LAT boresight at the GBM trigger time is 68 
degrees.

The GBM light curve shows/consists of five pulses
with a duration (T90) of about 18.2 s (50-300 keV).
The time-averaged spectrum from T0-0.5 s to T0+20.0 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -1.1 +/- 0.1 and
the cutoff energy, parameterized as Epeak, is 129.0 +/- 9.5 keV.

The event fluence (10-1000 keV) in this time interval is
(4.8 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+11.8 s in the 10-1000 keV band
is 7.1 +/- 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: GRB160310A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19162
SUBJECT: GRB 160310A: Swift-XRT observations
DATE:    16/03/10 18:58:39 GMT
FROM:    Alessandro Maselli at INAF/IASF Palermo  <maselli@ifc.inaf.it>

S.L. Gibson (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (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) 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 160310A (Vianello et al. GCN Circ. 19158),
collecting 3.0 ks of Photon Counting (PC) mode data between T0+40.3 ks
and T0+46.7 ks. 

One uncatalogued X-ray source has been detected inside or close to the
Fermi/LAT error region, 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 2:
  RA (J2000):  98.8226  =  06:35:17.42
  Dec (J2000): -7.2156  =  -07:12:56.1
  Error: 5.1 arcsec (radius, 90% conf.)
  Count-rate: (5.2 +/- 1.9)e-3 ct s^-1
  Flux: (1.18 +/- 0.43)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Another uncatalogued was also detected, however this was too far from
the GRB position to be the afterglow.

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/00020602.

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


GRB_name: GRB160310A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19163
SUBJECT: GRB 160310A: LCOGT-SAAO optical upper limits
DATE:    16/03/10 19:53:37 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

D. Xu (NAOC/CAS) reports on behalf of a collaboration:

We observed the field of GRB 160310A (Vianello et al., GCN 19158) using 
the LCOGT 1-m located at Sutherland, South Africa. Observations started 
at 18:57:18 UT on 2016-03-10 (i.e., 18.75 hr after the burst) and 2x300s 
frames were obtained in R- and I-band each.

No credible source is detected within or at the edge of the error circle 
of  the XRT Source 2 reported in Gibson et al. (GCN 19162), down to 
limiting magnitudes of R~20.0 and I~18.6, respectively.

[GCN OPS NOTE(10mar16): Per author's request, "SSO" was changed to "SAAO".]


GRB_name: GRB160310A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19164
SUBJECT: GRB 160310A: NOT optical observations
DATE:    16/03/10 21:55:00 GMT
FROM:    Thomas Kruehler at MPE Garching  <kruehler@mpe.mpg.de>

T. Kruehler (MPE Garching), A. de Ugarte Postigo (IAA-CSIC, DARK/NBI),
D. Malesani (DARK/NBI), and T. Kuutma (NOT) report on behalf of a
larger collaboration:

We observed the field of GRB 160310A (Vianello et al., GCN #19158,
Toelge & Hui, GCN #19161) with the NOT equipped with ALFOSC.
Imaging in the i-band filter started at 20:40:57 UT on
2016-03-10, 20.3 hr after the GRB trigger.

In a combined image of 5x120 s exposure time, we detect a single
source in the XRT error circle (Gibson et al. GCN#19162) at a
position of

RA (J2000) = 06:35:17.33
Dec. (J2000) = -07:12:56.0

with an uncertainty of 0".5 in each coordinate.

Calibrating our image against I-band magnitudes from field stars
of the USNO-B1 catalog, we measure a preliminary brightness of

I = 21.4 +- 0.2 mag

not corrected for the expected foreground extinction corresponding
to a reddening of E_B-V = 0.486 mag (Schlafly & Finkbeiner 2011)

The field is relatively crowded, and chance coincidences in the 5.1"
error circle are not unlikely. No statement about possible variability
can be made at this point.


GRB_name: GRB160307A
Detection_method: CALET
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19165
SUBJECT: GRB 160307A: CALET Gamma-Ray Burst Monitor detection of a possible short GRB
DATE:    16/03/11 10:11:33 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto@phys.aoyama.ac.jp>

S. Torii (Waseda U), A. Yoshida, T. Sakamoto, I. Takahashi, Y. Kawakubo, K. Senuma, 
M. Moriyama, Y. Yamada (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka, 
S. Ozawa (Waseda U),  Y. Shimizu, T. Tamura (Kanagawa U), W. Ishizaki (ICRR), 
M. L. Cherry (LSU), S. Ricciarini (U of Florence) P. S. Marrocchesi (U of Siena) 
and the CALET collaboration:

A possible short-duration GRB160307A (trigger #1141348444) triggered the CALET 
Gamma-Ray Burst Monitor (CGBM) at 01:18:34.96 on 7 March 2016.  The burst signal 
was detected by SGM instrument.  

The light curve of the SGM shows a single peak.  The emission starts and peaks 
at T0-0.3 sec and ends at T0+0.2 sec.   The T90 duration measured by the SGM data 
is 0.4 +- 0.2 sec (40-1000 keV). 

Identification of this possible short event by other spacecraft is strongly encouraged.  

The CGBM data used in this analysis are provided by the Waseda CALET Operation Center 
located at the Waseda University.


GRB_name: GRB160310A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19166
SUBJECT: GRB 160310A: RATIR Optical and NIR Observations
DATE:    16/03/11 14:05:14 GMT
FROM:    Eleonora Troja at GSFC  <eleonora.troja@nasa.gov>

Eleonora Troja (GSFC), Nat Butler (ASU), Alan M. Watson (UNAM), 
Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer 
(UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), 
Antonino Cucchiara (GSFC/STScI), 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 the Fermi GRB 160310A (Vianello, et al., GCN 
19158; Toelge, et al., GCN 19161) 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 2016/03 11.16 to 2016/03 11.32 UTC (27.46 to 31.25 hours 
after the GBM trigger).

We observed the two uncatalogued X-ray sources detected by the Swift/XRT 
(Gibson, et al., 19162). For source #1 we obtained a total of 1.07 hours 
exposure in the r and i bands and 0.45 hours exposure in the J, and H 
bands. For a source within the XRT error circle, in comparison with the 
USNO-B1 and 2MASS catalogs, we obtain the following detections:

   r    19.89 +/- 0.02
   i    19.34 +/- 0.01
   J    18.03 +/- 0.01
   H    17.37 +/- 0.01

These values are consistent with the magnitudes of a USNO-B1 catalogued 
object. No other source is visible within the XRT localization.

For source#2 we obtained a total of 1.78 hours exposure in the r and i 
bands and 0.75 hours exposure in the J, and H bands. For a source within 
the XRT error circle, in comparison with the USNO-B1 and 2MASS catalogs, 
we obtain the following detections:

   r    22.48 +/- 0.09
   i    21.82 +/- 0.05
   J    20.62 +/- 0.10
   H    20.03 +/- 0.08

These magnitudes are in the AB system and are not corrected for Galactic 
extinction in the direction of the GRB. Our values are slightly fainter 
than the NOT detection (Kruehler, et al., GCN 19164), although no strong 
claim about variability can be made at this time. Further observations 
to determine the nature of source #2 are encouraged.

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


GRB_name: GRB160310A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19167
SUBJECT: Konus-Wind observation of GRB 160310A (possible ultra-long GRB?)
DATE:    16/03/11 17:33:47 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred@mail.ioffe.ru>

D. Frederiks, S. Golenetskii, R.Aptekar, 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 GRB 160310A (Fermi/LAT detection: Vianello et al., GCN 19158;
Fermi/GBM detection: Toelge & Hui, GCN 19161)
triggered Konus-Wind at T0=1391.997 s UT (00:23:11.997).

The light curve shows a multi-peaked pulse which started
at ~T0-14 s and lasted until ~T0+15 s (the total duration is ~30 s).
The emission is seen up to ~4 MeV.

As observed by Konus-Wind, the burst had a fluence of
(6.8 Â± 1.5)x10^-6 erg/cm2 and a 64-ms peak energy flux,
measured from T0-0.192, of (2.1 Â± 0.4)x10^-6 erg/cm2
(both in the 20 keV - 10 MeV energy range).

The spectrum of the burst (measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 10 MeV range by a cutoff power-law
(CPL) function with the following model parameters:
the photon index alpha = -1.40(-0.16,+0.21),
and the peak energy Ep = 316(-95,+206) keV,
chi2 = 89/85 dof.
Fitting this spectrum with the GRB (Band) function yields
the same alpha and Ep with only an upper limit on beta of -2.0,
chi2 = 89/94 dof.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB160310_T01391/

In the KW waiting mode data, GRB 160310A was preceded by
a weaker, GRB-like event lasting from ~T0-1510 s to ~T0-1418 s
(the total duration is ~90 s).
Modeling the KW 3-channel spectrum for this episode
by the CPL function yields alpha = -1.23 Â± 0.24, Ep = 142 Â± 57 keV,
and a 20--1500 keV fluence of (7.7 Â± 1.7)x10^-6 erg/cm2.
The KW ecliptic latitude response for this event is consistent
with that for GRB 160310A. Taking this into account,
we suggest a possibility that GRB 160310A is, in fact,
a double-episode, ultra-long GRB with a total duration of ~1500 s.

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


GRB_name: GRB160310A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19168
SUBJECT: GRB 160310A: Swift/UVOT Upper Limits
DATE:    16/03/11 22:47:55 GMT
FROM:    Frank Marshall at GSFC  <femarsha@khamseen.gsfc.nasa.gov>

F. E. Marshall (NASA/GSFC) and A. Maselli (INAF/IASF)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 160310A
40247 s after the LAT trigger (Vianello et al., GCN Circ. 19158).
No source is detected in the initial UVOT exposures
at a position consistent with the position
of the possible XRT afterglow (Gibson et al., GCN Circ. 19162)
or the possible optical counterpart (Kruehler et al., GCN Circ. 19164).
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

u                40247        46726         1273         >20.4
white            41072        41890          805         >21.3
v                41897        42757          843         >19.9

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.53 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB160310A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19169
SUBJECT: GRB 160310A: Further NOT observations
DATE:    16/03/12 15:01:05 GMT
FROM:    Thomas Kruehler at MPE Garching  <kruehler@mpe.mpg.de>

T. Kruehler (MPE Garching), G. Leloudas (Weizmann Institute, DARK/NBI),
D. Malesani (DARK/NBI), and T. Kuutma (NOT) report on behalf of a
larger collaboration:

We again observed the field of GRB 160310A (Vianello et al., GCN #19158,
Toelge & Hui, GCN #19161) with the NOT equipped with ALFOSC.
A second epoch of imaging in the I-band filter was obtained starting at
20:21:05 UT on 2016-03-11, 48.0 hr after the GRB trigger.

In a combined image of 5x120 s exposure time, we still detect
the same source in the XRT error circle at a brightness comparable to
the observations 24 hours earlier (Kruehler et al., GCN #19164, see
also Troja et al., GCN #19166), indicating that it is likely not the
optical afterglow of GRB 160310A.


GRB_name: GRB160310A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19170
SUBJECT: GRB 160310A: MASTER-Kislovods observations 
DATE:    16/03/12 18:06:02 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

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

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


MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in Kislovodsk was pointed to the  GRB160310.02 23 sec after notice 
time and 56663 sec after trigger time at 2016-03-10 16:07:21 UT. We not 
found optical transient around and  inside  LAT 
error-box (ra=06 35 05 dec=-07 06 34 r=1 degree) brighter then 19.0 .

The message may be cited.


GRB_name: GRB160313A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19171
SUBJECT: GRB 160313A: Swift detection of a burst
DATE:    16/03/13 02:52:40 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

A. D'Ai (INAF-IASFPA), S. D. Barthelmy (GSFC), D. N. Burrows (PSU),
A. Y. Lien (GSFC/UMBC), A. Maselli (INAF-IASFPA),
L. M. McCauley (PSU), D. M. Palmer (LANL),
B. Sbarufatti (INAF-OAB/PSU), M. H. Siegel (PSU) and
T. N. Ukwatta (LANL) report on behalf of the Swift Team:

At 02:37:15 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160313A (trigger=678929).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 183.788, +57.293 which is 
   RA(J2000)  =  12h 15m 09s
   Dec(J2000) = +57d 17' 34"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows several peaks
with a total duration of about 40 sec.  The peak count rate
was ~1000 counts/sec (15-350 keV), at ~30 sec after the trigger. 

The XRT began observing the field at 02:39:48.3 UT, 152.5 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 183.7969, 57.2840 which
is equivalent to:
   RA(J2000)  = 12h 15m 11.24s
   Dec(J2000) = +57d 17' 02.3"
with an uncertainty of 2.2 arcseconds (radius, 90% containment). This
location is 36 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. No
spectrum from the promptly downlinked event data is yet available to
determine the column density. 

UVOT took a finding chart exposure of 150 seconds with the White
filter  starting 198 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 0.01. 

Burst Advocate for this burst is A. D'Ai (antonino.dai AT ifc.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: GRB160313A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19172
SUBJECT: GRB 160313A: SAO RAS observations
DATE:    16/03/13 03:24:53 GMT
FROM:    Moskvitin Alexander at SAO RAS  <mosk@sao.ru>

A. Moskvitin (SAO RAS, Russia) report on behalf of the larger team.


The field of GRB 160313A (D'Ai et al., GCNC #19171) was observed
with the SAO RAS Zeiss-1000 telescope. The observations started during
the morning twilight, since 10 minutes after the trigger.

In combined image of 4 x 60 seconds in the Rc band we did not detect
any object within the XRT error circle down to the limiting magnitude
R_lim = 18.2. This estimation based on the nearby USNO-B1 stars.


GRB_name: GRB160313A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19173
SUBJECT: GRB 160313A: RATIR Optical and NIR Observations
DATE:    16/03/13 05:53:49 GMT
FROM:    Antonino Cucchiara at NASA/GSFC  <antonino.cucchiara@nasa.gov>

Antonino Cucchiara (GSFC/STScI), Nat Butler (ASU), Alan M. Watson
(UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G.
Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom
(UCB), 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 160313A (D'Ai, et al., GCN 19171) 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 2016/03 13.14 to 2016/03 13.22 UTC (0.63
to 2.67 hours after the BAT trigger), obtaining a total of 1.42 hours
exposure in the r and i bands and 0.52 hours exposure in the Z,
Y, J, and H bands.


For a source within the Swift-XRT error circle, in comparison with the 
SDSS DR9 and 2MASS catalogs, we obtain the following upper limits (3-sigma):

  r > 23.49
  i > 23.21
  Z > 22.08
  Y > 21.48
  J > 20.11
  H > 20.60

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 AstronÃ³mico Nacional in San Pedro 
MÃ¡rtir.


GRB_name: GRB160313A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19174
SUBJECT: GRB 160313A: Enhanced Swift-XRT position
DATE:    16/03/13 08:12:04 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 722 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 160313A, 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 = 183.79649, +57.28347 which is equivalent
to:

RA (J2000): 12h 15m 11.16s
Dec (J2000): +57d 17' 00.5"

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: GRB160313A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19175
SUBJECT: GRB 160313A: TAROT Calern observatory optical observations
DATE:    16/03/13 11:47:05 GMT
FROM:    Alain Klotz at IRAP-CNRS-OMP  <Alain.Klotz@free.fr>

Klotz A., Turpin D., Atteia J.L. (CNRS-OMP-IRAP),
Boer, M., Laugier, R. (CNRS-ARTEMIS),
Gendre B. (UVI - Etelman Obs.) report:

We imaged the field of GRB 160313A detected by SWIFT
(trigger 678929) with the TAROT robotic telescope (D=25cm)
located at the Calern observatory, France.

The observations started 122s after the GRB trigger
(20s after the notice). The elevation of the field decreased from
64 degrees above horizon and weather conditions
were good but images are slightly defocused.

The first image is trailed with a duration of 60.0s
(see the description in Klotz et al., 2006, A&A 451, L39).
We do not detect any OT in the XRT error box published
by Goad et al. (GCNC 19174). Next images are recorded
with diurnal tracking.

t1(s) t2(s)  Rmag_lim  Site
  122   182   15.8      TAROT Calern
  198   228   16.9      TAROT Calern
  239   269   16.8      TAROT Calern
  280   393   18.7      TAROT Calern
  405  1226   18.7      TAROT Calern
1237  3172   19.2      TAROT Calern

Magnitudes were estimated with nearby USNO-B1 stars
and are not corrected for galactic dust extinction.


GRB_name: GRB160313A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19176
SUBJECT: GRB 160313A: Swift-XRT refined Analysis
DATE:    16/03/13 12:56:17 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

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

We have analysed 7.1 ks of XRT data for GRB 160313A (D'Ai et al. GCN
Circ. 19171), from 138 s to 22.9 ks after the  BAT trigger. The data
comprise 39 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. 19174).

The light curve can be modelled with a power-law decay with a decay
index of alpha=3.23 (+0.18, -0.16).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.9 (+/-0.4). The
best-fitting absorption column is  1.7 (+1.4, -1.1) x 10^21 cm^-2, in
excess of the Galactic value of 1.3 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 3.8 x 10^-11 (4.8 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      1.7 (+1.4, -1.1) x 10^21 cm^-2
Galactic foreground: 1.3 x 10^20 cm^-2
Excess significance: 2.3 sigma
Photon index:      1.9 (+/-0.4)

If the light curve continues to decay with a power-law decay index of
3.23, the count rate at T+24 hours will be 1.1 x 10^-8 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.0 x
10^-19 (5.0 x 10^-19) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00678929.

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


GRB_name: GRB160313A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19177
SUBJECT: GRB 160313A: LT observations
DATE:    16/03/13 13:28:15 GMT
FROM:    Cristiano Guidorzi at Ferrara U,Italy  <guidorzi@fe.infn.it>

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

The 2-m Liverpool Telescope began observing Swift GRB 160313A (D'Ai et 
al., GCN 19171) on March 13, 02:40:45 UT (3.5 minutes after the burst 
trigger). Inside the XRT error circle (Goad et al., GCN 19174) we find 
no source down to r'> 21.0 mag in a 6x10s exposure (at 36.5 min, mid 
time), as calibrated against nearby SDSS stars, in agreement with 
previous reports (Moskvitin et al. GCN 19172; Cucchiara et al. GCN 
19173; Klotz et al. GCN 19175).


GRB_name: GRB160313A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19178
SUBJECT: GRB 160313A: MASTER-Net optical observations 
DATE:    16/03/13 15:54:59 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

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

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

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

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

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 Kislovodsk was pointed to the  GRB160313A 21 sec after notice 
time and 129 sec after trigger time at 2016-03-13 02:39:24 UT in two 
polarizations. On our first (30s exposure) and following coadd images 
we haven't found optical transient  within SWIFT error-box (D'Ai et al GCN 
19171). The observations took during the morning twilight. We have a 5 
good images before they become overexposed.

The 5-sigma upper limit has been about 16.5 on first single (30s exposure) 
image and 17.2 on coadd (300 s exposure) image.

The message may be cited.


GRB_name: GRB160313A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19179
SUBJECT: GRB 160313A: Chante-Perdrix Observatory optical observations
DATE:    16/03/13 19:21:44 GMT
FROM:    Alain Klotz at IRAP-CNRS-OMP  <Alain.Klotz@free.fr>

Kugel F., Rinner C. (Observatoire Chante-Perdrix, Dauban),
and Klotz A. (CNRS-OMP-IRAP) report:

F. Kugel imaged the field of GRB 160313A detected by SWIFT
(trigger 678929) with the D=40cm F/D=3 telescope
located at the Observatoire Chante-Perdrix, Dauban,
France (IAU station A77). The CCD camera is
ARTEMIS ATIK-460ex, no optical filter is used.

The observations started 17.4 min after the GRB trigger.

The first image is 60 second exposure.
No optical transcient is detected in the XRT
error box published by Goad et al. (GCNC 19174).
Next images are co-added:

t1(min) t2(min)  Rmag_lim
17.4    18.4     19.5
17.4    42.4     20.0

Magnitudes were estimated with nearby USNO-B1 stars
and are not corrected for galactic dust extinction.


GRB_name: GRB160313A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19181
SUBJECT: GRB 160313A, Swift-BAT refined analysis
DATE:    16/03/13 21:59:08 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), A. D'Ai (INAF-IASFPA),
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-691 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 160313A (trigger #678929)
(A. D'Ai et al., GCN Circ. 19171).  The BAT ground-calculated position is
RA, Dec = 183.821, 57.278 deg which is
  RA(J2000)  =  12h 15m 17.0s
  Dec(J2000) = +57d 16' 40.1"
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 80%.

The mask-weighted light curve shows a complex structure with several
overlapping pulses. The structure starts at ~ T-5 s and ends at ~ T+45 s.
T90 (15-350 keV) is 42.6 +- 6.4 sec (estimated error including systematics).

The time-averaged spectrum from T-5.6 to T+44.7 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.36 +- 0.23.  The fluence in the 15-150 keV band is 5.8 +- 0.8 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+24.79 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.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/678929/BA/


GRB_name: GRB160314A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19182
SUBJECT: GRB 160314A: Swift detection of a burst
DATE:    16/03/14 11:46:45 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),
L. Izzo (URoma1), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC),
F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester) and
B. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift Team:

At 11:32:51 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160314A (trigger=679120).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 112.781, +17.001 which is 
   RA(J2000) = 07h 31m 07s
   Dec(J2000) = +17d 00' 03"
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 about 20 sec. The peak count rate
was ~1700 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 11:34:22.7 UT, 91.0 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 112.7891, 16.9987 which
is equivalent to:
   RA(J2000)  = 07h 31m 09.39s
   Dec(J2000) = +16d 59' 55.5"
with an uncertainty of 2.1 arcseconds (radius, 90% containment). This
location is 29 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. No
spectrum from the promptly downlinked event data is yet available to
determine the column density. 

UVOT took a finding chart exposure of 250 seconds with the U filter starting
151 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 19.2 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 18.0 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.08. 

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: GRB160314A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19183
SUBJECT: GRB 160314A: Weihai optical upper limit
DATE:    16/03/14 13:05:43 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

D. Xu (NAOC/CAS), Y.-D. Hu (IAA-CSIC), Y. Qing (Geneva Observatory), 
Y.-H. Han (NAOC/CAS, HUST), C.-M. Zhang, S.-M. Hu, C. Cao (SDU) report:

We observed the field of GRB 160314A (D'Elia et al., GCN 19182) using 
the 1-m telescope located at Weihai, Shandong, China. Observations 
started at 11:51:15 UT on 2016-03-14 (i.e., 18.4 min after the burst) in 
cloudy weather, and 4x300s R-band frames were obtained.

No optical source is detected within the XRT error circle (D'Elia et 
al., GCN 19182), down to a limiting magnitude of m(R)~19.0, calibrated 
with the SDSS field.


GRB_name: GRB160314A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19184
SUBJECT: GRB 160314A: ISON-Ussuriysk optical upper limit
DATE:    16/03/14 14:35:44 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

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

We observed the field of the GRB 160314A (D'Elia et al., GCN  19182) 
with SANTEL-650 (0.65m)  telescope of UAFO/ISON-Ussuriysk observatory 
starting on March, 14 (UT) 11:32:51. We obtained series of unfiltered 
images of 30 s exposure. We do not detect  any optical afterglow within 
XRT error circle  (D'Elia et al., GCN 19182). Photometry of a combined 
image of few first frames is following

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

2016-03-14 11:32:51  0.01728 none   3*30  n/d    18.7


The photometry is based on nearby  SDSS star J073110.29+170129.9
assuming R_Lupton = 16.132.


GRB_name: GRB160314A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19185
SUBJECT: GRB 160314A: Enhanced Swift-XRT position
DATE:    16/03/14 16:43:43 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 1542 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 160314A, 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 = 112.79093, +16.99938 which is equivalent
to:

RA (J2000): 07h 31m 9.82s
Dec (J2000): +16d 59' 57.8"

with an uncertainty of 3.2 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: GRB160228A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19186
SUBJECT: GRB 160228A: GROND afterglow confirmation and X-shooter host candidate redshift
DATE:    16/03/14 17:46:43 GMT
FROM:    Thomas Kruehler at MPE Garching  <kruehler@mpe.mpg.de>

T. Kruehler (MPE Garching), D. Malesani (DARK/NBI), D. Xu (NAOC/CAS),
J. Bolmer (MPE Garching), J. P. U. Fynbo, D. Perley (both DARK/NBI),
D. A. Kann (TLS Tautenburg), J. Greiner and J. F. Graham (both MPE
Garching) report on behalf of a larger collaboration:

We re-observed the field of GRB 160228A (Swift-trigger 676595,
Malesani et al. GCN #19107) with GROND mounted at the 2.2m MPG
telescope at ESO La Silla observatory. Simultaneous observations
in seven filters (g'r'i'z'JHK) started at 01:13 UT on 2016-03-03
(80 h after the GRB) and consisted of images with a total
integration time of 72 minutes in g'r'i'z' and 60 minutes in JHK.

The source reported as candidate afterglow in our earlier imaging
(Delvaux et al. GCN #19114) has faded beyond the detection limit
of the new data (r' > 25.1 mag in the AB system), confirming it
as the optical afterglow of GRB 160228A.

The nearby source (angular separation of 1.7") mentioned in
Delvaux et al. (GCN #19114) is still clearly present and located
at

RA (J2000) = 07:09:15.79
Dec. (J2000) = +26:55:52.4

with a preliminary brightness of r' = 24.2 +/- 0.3 mag.

The chance coincidence probability of finding an unrelated object
of this magnitude within a distance of 1.7" is 0.04
(following Bloom et al. 2002, AJ, 123, 1111), and we hence
consider this object as a host galaxy candidate of GRB 160228A.
While the chance coincidence probability is quite low, we note
that the angular separation would be unusually large for long GRBs.

A spectrum of the possible host was taken on 2016-03-12 with the VLT
equipped with the X-shooter spectrograph. The spectrum covers
the wavelength range 3000-20000 AA and has an exposure time of
4x1200 s.  In the red part of the spectrum, we detect two emission
lines which we interpret as [O III] (5007) and Halpha at a common
redshift z = 1.64.

We acknowledge excellent support from the observing staff at
La Silla and Paranal, in particular Giovanni Carraro,
Boris Haeussler, Jose Velasquez, and Willem-Jan de Wit.


GRB_name: GRB160314A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19187
SUBJECT: GRB 160314A: Swift/UVOT Detection
DATE:    16/03/14 19:04:28 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <siegel@swift.psu.edu>

M. H. Siegel (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 160314A
151 s after the BAT trigger (D'Elia et al., GCN Circ. 19182).
A source consistent with the XRT position
(Osborne et al. GCN Circ. 19185)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
  RA  (J2000) =  07:31:09.73 = 112.79053 (deg.)
  Dec (J2000) = +16:59:59.1  =  16.99974 (deg.)
with an estimated uncertainty of 0.63 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

v                  457         1825          175        >19.6
b                  407         1775          175        >19.6
u                  151          401          246         19.14 +/- 0.16
w1                 506         1726          156        >18.8
m2                 481         1849          174        >19.2
w2                 432         1801          175        >19.3

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).


GRB_name: GRB160314A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19188
SUBJECT: GRB 160314A: Swift-BAT refined analysis
DATE:    16/03/14 19:12:30 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), V. D'Elia (ASDC),
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 160314A (trigger #679120)
(D'Elia et al., GCN Circ. 19182).  The BAT ground-calculated position is
RA, Dec = 112.766, 17.024 deg which is
  RA(J2000)  =  07h 31m 03.9s
  Dec(J2000) = +17d 01' 24.7"
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 75%.

The mask-weighted light curve shows a single-pulse structure that starts
at ~ T0, peaks at ~ T+1 s, and ends at ~ T+9 s. T90 (15-350 keV)
is 8.73 +- 1.52 sec (estimated error including systematics).

The time-averaged spectrum from T-0.04 to T+9.31 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.53 +- 0.22.  The fluence in the 15-150 keV band is 2.8 +- 0.4 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+1.12 sec in the 15-150 keV band
is 0.9 +- 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/679120/BA/


GRB_name: GRB160314A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19189
SUBJECT: GRB 160314A: Optical observations from OSN
DATE:    16/03/14 20:42:32 GMT
FROM:    Antonio de Ugarte Postigo at IAA-CSIC  <deugarte@iaa.es>

A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), F. Aceituno (IAA-CSIC),
C.C. Thoene (IAA-CSIC), L. Izzo (Uroma1), Z. Cano (U. Iceland) report:

We observed the field of GRB 160314A (Dâ€™Elia et al., GCN 19182) with the 1.5 m 
Telescope at the Sierra Nevada Observatory, starting at 19:07 UT (7.57 hr after the
burst). Observations were performed under non-optimal conditions, being affected 
by passing clouds. In a 5x300s exposure obtained in R-band we do not detect 
the optical counterpart candidate (Siegel et al, GCN 19187) down to a 3-sigma 
limiting magnitude of R ~ 21.0, as compared to USNO-B1.0 stars.


GRB_name: GRB160314A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19190
SUBJECT: GRB 160314A: Swift-XRT refined Analysis
DATE:    16/03/14 22:31:49 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

K.L. Page (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), C. Pagani (U. Leicester), A.P.
Beardmore (U. Leicester) and V. D'Elia report on behalf of the
Swift-XRT team:

We have analysed 7.9 ks of XRT data for GRB 160314A (D'Elia et al. GCN
Circ. 19182), from 77 s to 24.8 ks after the  BAT trigger. The data
comprise 6 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.
19185).

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.38 (+/-0.11).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.02 (+0.22, -0.15). The
best-fitting absorption column is  6.7 (+5.2, -0.5) x 10^20 cm^-2,
consistent with the Galactic value of 6.2 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 3.2 x 10^-11 (3.8 x
10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      6.7 (+5.2, -0.5) x 10^20 cm^-2
Galactic foreground: 6.2 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:      2.02 (+0.22, -0.15)

If the light curve continues to decay with a power-law decay index of
1.38, the count rate at T+24 hours will be 1.8 x 10^-4 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 6.0 x
10^-15 (7.0 x 10^-15) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00679120.

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


GRB_name: GRB160314A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19191
SUBJECT: GRB 160314A: NOT afterglow observations
DATE:    16/03/14 22:35:45 GMT
FROM:    Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst  <malesani@dark-cosmology.dk>

D. Malesani (DARK/NBI), A. de Ugarte Postigo (IAA-CSIC and DARK/NBI), T. 
Kruehler (MPE Garching), A. Kvammen (Univ. Tromsoe, Norway, and NOT), 
report on behalf of a larger collaboration:

We observed the optical counterpart of GRB 160314A (D'Elia et al., GCN 
19182; Siegel & D'Elia, GCN 19187) with the Nordic Optical Telescope 
(NOT) equipped with the AlFOSC imager. Our observations were carried out 
in the r and i bands, and started on 2016 March 14.86 (9.07 hr after the 
GRB).

An object at a position consistent with the UVOT object is detected in 
both filters. We measure its coordinates to be (J2000; 0.3" uncertainty):

RA =  07:31:09.73
Dec = +16:59:58.7

At a mean epoch of Mar 14.865 UT, we measure for the afterglow r = 22.40 
+- 0.06 (AB), calibrated against nearby SDSS stars. We thus confirm the 
UVOT object as the afterglow of GRB 160314A.

We note that a faint object is marginally detected at the afterglow 
position in the SDSS data, visible after stacking the gri images. This 
could be a relatively bright host galaxy for GRB 160314A. A finding 
chart is available at the following link:

http://www.astro.ku.dk/~malesani/GRB/160314A/160314A_NOT_SDSS.jpg


GRB_name: GRB160314A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19192
SUBJECT: GRB 160314A: VLT/X-shooter redshift
DATE:    16/03/15 08:59:11 GMT
FROM:    Valerio D'Elia at ASDC  <delia@asdc.asi.it>

V. D'Elia (INAF-OAR/ASI-ASDC), D. Xu (NAOC/CAS), D. Malesani, J. P. U. Fynbo (DARK/NBI), H. Flores (GEPI/Paris obs), K. Wiersema (U. of Leicester) and D. Watson (DARK/NBI) report on behalf of a larger collaboration:

We observed the afterglow of GRB 160314A (D'Elia et al., GCN 19182) with ESO's Very Large Telescope UT2 equipped with X-shooter.

Our observations started at 00:15:42 UT on 2016 March 15, about 12h 45m after the Swift trigger, and consisted of four spectra of 1200 s each. The X-shooter spectra cover the range between 3000 and 21000 AA, and were obtained at a seeing of around 0.7.

A preliminary analysis of the spectrum shows several emission features at the position of the optical transient (Siegel and D'Elia, GCN 19187; Malesani et al. GCN 19191), which we interpret as emission lines of Halpha, Hbeta, Hgamma, [O III], [O II], [S III] and [N II] from the host galaxy at redshift 0.726. Weak absorption features due to Fe II levels are marginally detected at the same redshift.

We acknowledge the fast and efficient support provided by Paranal staff. In particular we thank Boris Haeussler, Giovanni Carraro, Jose Velasquez, Willem-Jan de Wit and Henri Boffin for their excellent job. We also thank Jens Hoeijmakers for postponing his visitor programme allowing us to perform this observation. 


GRB_name: GRB160313A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19194
SUBJECT: GRB 160313A: Swift/UVOT Upper Limits
DATE:    16/03/15 16:18:15 GMT
FROM:    Marissa McCaule at PSU  <marissamc@swift.psu.edu>

L. M. McCauley (PSU) and A. D'Ai (INAF-IASFPA) reports on behalf of the
Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 160313A
198 s after the BAT trigger (D'Ai et al., GCN Circ. 19171).
No optical afterglow consistent with the XRT position
(Goad et al. GCN Circ. 19174) 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              198         920         418        >20.77
white                 198        5756         664        >21.01
v                     355        6167         451        >19.78
b                     454        5552         254        >20.24
u                     430        6588         260        >19.44
uvw1                  405        6577         451        >19.93
uvm2                 4737        6372         393        >19.17
uvw2                 4328        5962         393        >19.99


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).


GRB_name: GRB160314A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19195
SUBJECT: GRB 160314A: Mondy optical observations
DATE:    16/03/15 19:09:27 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

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

We observed the field of the GRB 160314A (D'Elia et al., GCN  19182) with 
AZT-33IK telescope of Sayan observatory (Mondy)  starting on March, 14 (UT) 
16:13:52.  The optical counterpart of GRB 160314A (D'Elia et al., GCN 19182; 
Siegel & D'Elia, GCN 19187) is clearly visible in a combined image. 
Preliminary photometry  of  the combined image is following

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

2016-03-14  16:13:52  0.21784  R       64*60  21.82  0.18

SDSS-DR9_id                R(Lupton)
J073110.30+170129.8    16.13
J073114.43+170052.5    17.95
J073119.52+170015.1    17.13
J073110.88+170047.1    19.53
J073104.14+170112.8    19.88


GRB_name: GRB160314A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19196
SUBJECT: GRB 160314A: RATIR Optical and NIR Observations 
DATE:    16/03/15 20:32:00 GMT
FROM:    Alan M. Watson at Instituto de Astronomia UNAM  <alan@astro.unam.mx>

Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC),
William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J.
Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara
(GSFC/STScI), 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 160314A (D'Elia et al., GCN Circ. 19182)
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 2016/03 15.13 to
2016/03 15.36 UTC (15.59 to 21.16 hours after the BAT trigger),
obtaining a total of 3.56 hours exposure in the r and i bands and 1.49
hours exposure in the Z, Y, J, and H bands.

For a source within the Swift-XRT error circle (Osborne et al., GCN
Circ. 19185), in comparison with the SDSS DR9 and 2MASS catalogs, we
obtain the following detections and 3-sigma upper limit:

 r 22.83 +/- 0.10
 i 22.37 +/- 0.06
 Z 22.27 +/- 0.15
 Y 22.40 +/- 0.21
 J 21.93 +/- 0.19
 H > 22.38

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

Compared to the NOT observations reported by Malesani et al. (GCN Circ.
19191), we detect fading in r at the 3.7-sigma level between mean epochs
of 9.2 and 18.4 hours after the bursts. This confirms that the NOT
source is the optical counterpart of the GRB.

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


GRB_name: GRB160314B
Detection_method: Fermi LAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19197
SUBJECT: GRB 160314B: Fermi-LAT detection
DATE:    16/03/15 22:29:29 GMT
FROM:    Judith Racusin at GSFC  <judith.racusin@nasa.gov>

G. Vianello (Stanford), J. Racusin (NASA/GSFC), D. Kocevski (NASA/GSFC), F. Longo (University of 
Trieste and INFN), and B. Ahlgren (KTH), report on behalf of the Fermi-LAT team:

At 22:17:53.73 on March 14, 2016 Fermi-LAT detected high-energy emission from GRB 160314B, which 
was also detected by Fermi-GBM (trigger 479686676 / 160314929). 

The best LAT on-ground location is found to be:
RA, Dec (J2000) = 167.56, 45.67 
with an error radius of 0.65 deg (90 % containment, statistical error only). 

Unfortunately, the LAT was not taking data at the trigger time T0, because Fermi was just exiting the South 
Atlantic Anomaly (SAA).  Note that LAT and GBM have slightly different SAA definitions in onboard software.  
However, LAT resumed data taking ~30 seconds after T0, and the GRB was 21 deg from the LAT boresight 
at that time. 

The LAT data show a significant increase in the event rate that is spatially and temporally 
correlated with the trigger with high significance. The highest-energy photon is a 900 MeV event which is 
observed ~630 seconds after the GBM trigger.

The Fermi-LAT point of contact for this burst is B. Ahlgren (bjornah@kth.se).

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: GRB160314B
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19198
SUBJECT: GRB 160314B: Fermi GBM observation
DATE:    16/03/16 01:06:32 GMT
FROM:    C. Michelle Hui at MSFC/Fermi-GBM  <c.m.hui@nasa.gov>

C. M. Hui (NASA/MSFC) report on behalf of the Fermi GBM Team:

At 22:17:53.73 UT on 14 March 2016, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 160314B (trigger 479686677 / 160314929),
which was also detected by the LAT (G. Vianello et al., GCN 19197). 
GBM triggered on this GRB ~70s after exiting the SAA. 
The GBM on-ground location is consistent with the LAT position.

The angle from the Fermi LAT boresight at the GBM trigger time 
is 21 degrees.

The GBM light curve shows two peaks with a duration (T90) 
of about 100 s (50-300 keV). The time-averaged spectrum 
from T0-5.6 s to T0+18.9 s is best fit by a power law function 
with an exponential high-energy cutoff.  The power law index 
is -1.19 +/- 0.05 and the cutoff energy, parameterized as Epeak, 
is 954.5 +/- 274.0 keV.

The event fluence (10-1000 keV) in this time interval is
(8.98 +/- 0.34)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+8.4 s in the 8-1000 keV band
is 3.25 +/- 0.24 ph/s/cm^2.

A Band function fits the spectrum equally well with
Epeak = 848.9 +/- 368.0 keV, alpha = -1.20 +/- 0.06,
and beta = -1.86 +/- 0.22.

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


GRB_name: GRB160314A
Detection_method: correction
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19199
SUBJECT: GRB 160314A: ISON-Ussuriysk optical upper limit, updated photometry and correction of GCN 19184
DATE:    16/03/16 06:14:44 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

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

After receiving full data set of our observations (GCN 19184) we refine 
photometry and correct UT time of the observations.

The field of the GRB 160314A (D'Elia et al., GCN  19182) was observed 
with SANTEL-650 (0.65m)  telescope of UAFO/ISON-Ussuriysk observatory 
starting on March, 14 (UT) 11:56:51 under clear sky but with a high 
ground wind speed. We obtained series of unfiltered images of 30 s 
exposure. In a combined image we do not detect optical afterglow 
(D'Elia et al., GCN 19182; Siegel & D'Elia, GCN 19187; Malesani et al., 
GCN 19191). Photometry of combined images  is following

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

2016-03-14 11:56:51  0.01728  none    3*30  n/d    18.7
2016-03-14 11:56:51  0.04575  none   30*30  n/d    20.1

The photometry is based on nearby  SDSS star J073110.29+170129.9
assuming R_Lupton = 16.132.


GRB_name: GRB160314A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19200
SUBJECT: GRB 160314A: GROND optical/NIR observations
DATE:    16/03/16 15:55:55 GMT
FROM:    Jan Bolmer at MPE/Garching  <jan@bolmer.de>

T. Schweyer, J. Bolmer and J. Greiner (all MPE Garching) report on
behalf of the GROND team:

We observed the field of GRB 160314A (Swift trigger 679120; D'Elia et
al., GCN #19182) simultaneously in g'r'i'z'JHK with GROND (Greiner et al.
2008, PASP 120, 405) mounted at the 2.2m MPG telescope at the ESO La Silla
Observatory (Chile).

Observations started at 23:53 UT on 2016-03-15, 36.3h after the GRB
trigger. They were performed at an average seeing of 1.1" and at an
average airmass of 1.5.

We clearly detect the source reported by Malesani et al. (GCN #19191)
and Butler et al. (GCN #19196).

Based on 90 min of exposure in g'r'i'z' and 96 min in JHK, at a mid-time
of 00:44 UT on 2016-03-16, we derive the following preliminary magnitudes
and upper limits (all in the AB system):

g' = 23.3 +/- 0.1 mag,
r' = 23.1 +/- 0.1 mag,
i' = 22.6 +/- 0.1 mag,
z' = 22.5 +/- 0.1 mag,
J > 22.2 mag,
H > 21.8 mag, and
K > 20.4 mag.

Given detections and upper limits are calibrated against SDSS
as well as 2MASS field stars. No correction for the expected Galactic
foreground extinction corresponding to a reddening of E_(B-V)=0.07 mag in
the direction of the burst (Schlafly & Finkbeiner 2011) has been applied.

Our r'-band magnitude, combined with that of RATIR (Butler et al., GCN #19196)
suggests a very slow fading, possibly indicating that we are close to the
brightness of the host galaxy (Malesani et al. GCN #19191, D'Elia et al., GCN #19192).


GRB_name: GRB160313A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19201
SUBJECT: GRB 160313A: Mondy optical upper limit
DATE:    16/03/16 20:22:15 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

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

We observed the field of the GRB 160313A (D'Ai et al., GCN  19171) with 
AZT-33IK telescope of Sayan observatory (Mondy)  starting on March, 13 
(UT) 16:39:40.  We do not detect any source within enhanced Swift-XRT 
position (Goad et al., GCN 19174). Preliminary photometry  of  the 
combined image is following

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

2016-03-13  16:39:40  0.60586  R       30*120  23.6

Photometry is based on nearby SDSS-DR9 stars, Lupton transformations into R.

The nearest source to the enhanced XRT position is 5.5 arcsec East, in 
coordinates (J2000) 12:15:11.86 +57:17:00.0 with uncertainty of 0.5 
arcsec in both coordinates. The source magnitude is R=23.3+/-0.2. The 
source is not presented in SDSS-DR9 but barely visible in SDSS r-image.


GRB_name: GRB160314A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19202
SUBJECT: Continued RATIR Optical and NIR Observations
DATE:    16/03/16 22:00:02 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), Ori Fox
(STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara
(GSFC/STScI), 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), and Vicki Toy (UMD) report:

We observed the field of GRB 160314A (D'Elia et al., GCN 19182) 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 2016/03 16.12 to 2016/03 16.35 UTC (39.43 to
44.80 hours after the BAT trigger), obtaining a total of 3.56 hours
exposure in the r and i bands and 1.49 hours exposure in the Z, Y, J, and H
bands.

For a source within the Swift-XRT error circle (Osborne et al., GCN 19185),
in comparison with the SDSS DR9 and 2MASS catalogs, we obtain the following
detections and 3-sigma upper limit:

r      23.48 +/- 0.26
i      22.84 +/- 0.16
Z     22.08 +/- 0.17
Y     22.32 +/- 0.22
J      >  22.45
H     21.87 +/- 0.25

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB. Our observations (see, also, Butler
et al., GCN 19196) are consistent with a continued, slow source fading as
reported by the GROND team (Schweyer et al, GCN 19200).

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

GCN OPS NOTE(16Mar2016) Circular 19202 was mistakenly submitted without a GRB-name designation.
See 19203 for the corrected circular.  Per author's request 19202 was removed from the archive.


GRB_name: GRB160314A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19203
SUBJECT: GRB 160314A: Continued RATIR Optical and NIR Observations
DATE:    16/03/16 22:03:39 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), Ori Fox
(STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara
(GSFC/STScI), 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), and Vicki Toy (UMD) report:

We observed the field of GRB 160314A (D'Elia et al., GCN 19182) 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 2016/03 16.12 to 2016/03 16.35 UTC (39.43 to
44.80 hours after the BAT trigger), obtaining a total of 3.56 hours
exposure in the r and i bands and 1.49 hours exposure in the Z, Y, J, and H
bands.

For a source within the Swift-XRT error circle (Osborne et al., GCN 19185),
in comparison with the SDSS DR9 and 2MASS catalogs, we obtain the following
detections and 3-sigma upper limit:

r      23.48 +/- 0.26
i      22.84 +/- 0.16
Z     22.08 +/- 0.17
Y     22.32 +/- 0.22
J      >  22.45
H     21.87 +/- 0.25

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB. Our observations (see, also, Butler
et al., GCN 19196) are consistent with a continued, slow source fading as
reported by the GROND team (Schweyer et al, GCN 19200).

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


GRB_name: GRB160310A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19205
SUBJECT: GRB 160310A: A further Swift-XRT observation, no afterglow detected
DATE:    16/03/17 15:50:36 GMT
FROM:    Alessandro Maselli at INAF/IASF Palermo  <maselli@ifc.inaf.it>

A. Maselli (INAF-IASFPA) and P. A. Evans (U. Leicester) report on behalf 
of the Swift-XRT team:

On 2016 March 16, Swift-XRT has carried out a further observation of the 
field of GRB 160310A detected by Fermi (Vianello et al., GCN Circ. 
19158; Toelge and Hui, GCN Circ. 19161), collecting 4.0 ks of data from 
T0+569 ks to T0+599 ks. The X-ray source reported by Gibson et al. (GCN 
Circ. 19162) is still detected with a count rate of (5.5+/-1.8)E-03 
ct/s, showing no evidence of fading. Therefore, this source is not 
related to the GRB. The 3-sigma upper limit for the observation carried 
out between T0+40.3 ks and T0+46.7 ks, computed at the center of the 
Fermi-LAT error circle, is 3.8E-03 ct/s. We conclude that no afterglow 
has been identified by Swift-XRT for GRB 160310A.

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


GRB_name: GRB160131A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19206
SUBJECT: GRB 160131A: 15 GHz upper limits from AMI-LA
DATE:    16/03/17 19:13:30 GMT
FROM:    Kunal Mooley at Oxford U  <kunal.mooley@physics.ox.ac.uk>

K. P. Mooley, R. P. Fender, T. D. Staley (Oxford), G. Ghirlanda, F. 
Nappo (INAF, Merate), C. Rumsey, D. Titterington, S. Carey, J. Hickish, 
Y. C. Perrott, N. Razavi-Ghods, P. Scott (Cambridge), K. Grainge, A. 
Scaife (Manchester)

We observed the XRT position of GRB 160131A discovered by Swift (Page et 
al., GCN 18951; Goad et al., GCN 18958) at 15 GHz with the Arcminute 
Microkelvin Imager (AMI-LA) on 2016 Feb 24.79 UT and Mar 06.79 UT, 
corresponding to 24.5 days and 34.5 days post-burst respectively. We do 
not detect any radio source at the XRT location, with 3sigma upper 
limits of 150 uJy and 210 uJy respectively.

We thank the AMI scheduling team for carrying out these observations.


GRB_name: GRB160310A
Detection_method: IPN Triangulation
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19209
SUBJECT: IPN Triangulation of GRB 160310A
DATE:    16/03/19 21:42:04 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks, A. Kozlova,
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

S. Barthelmy, J. Cummings, N. Gehrels, H. Krimm, and D. Palmer,
on behalf of the Swift-BAT team, report:

The long-duration GRB 160310A was detected by Konus-Wind (Frederiks et 
al., GCN Circ. 19167), Fermi (LAT: Vianello et al., GCN Circ. 19158  and 
GBM: Toelge & Hui GCN Circ. 19167), and Swift (BAT), at about 1378 s UT 
(00:22:58). The burst was outside the coded field of view of the BAT.

We have triangulated it to a Konus-GBM annulus centered at 
RA(2000)=178.455 deg (11h 53m 49s)  Dec(2000)=-2.131 deg (-2d 07' 52"), 
whose radius is 76.571 +/- 0.876 deg (3 sigma) and to a Konus-BAT 
annulus centered at RA(2000)=178.592 deg (11h 54m 22s)  Dec(2000)=-2.265 
deg (-2d 15' 53"), whose radius is 76.187 +/- 1.716 deg (3 sigma).

While the GBM position is in a good agreement with both the Konus-GBM 
and the Konus-BAT annuli, the LAT position reported in GCN 19158 is 2.9 
deg (~10 sigma) from the Konus-GBM annulus center line. So we encourage 
further investigation of the LAT position.

Using the method suggested by Pal'shin, et al., ApJS 207, 38, 2013 (sec. 
4.2.1) and assuming a LAT error radius of 6 deg, we obtain the following 
joint LAT/IPN error box:
--------------------------------
  RA(2000), deg    Dec(2000), deg
--------------------------------
Center:
    101.726         -7.1445
Corners:
    100.850         -13.082
    102.648         -13.076
    102.726         -1.228
    100.975         -1.191
---------------------------------
The error box area is 21 sq. deg, and its maximum
dimension is 12 deg (the minimum one is 1.8 deg).

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB160310_T01391/IPN/


GRB_name: GRB160310A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19210
SUBJECT: GRB 160310A: Terskol 2-m observations
DATE:    16/03/21 07:40:35 GMT
FROM:    Moskvitin Alexander at SAO RAS  <mosk@sao.ru>

Ilia V. Sokolov (Terskol Peak Observatory), M. Andreev (Terskol Peak
Observatory), A. Sergeev (Terskol Peak Observatory),
A. Moskvitin (SAO RAS) report:

We observed the GRB160310A field 17h 57m 26s after the trigger (Fermi
trigger number 479262182) in R-band with a total exposure of 13 x 120 s.
We detected a source brighter than in SDSS images at
RA = 06:35:14.4
Dec = -07:03:49.0
with the R magnitude 20.34. The magnitude is not corrected
for the Galactic extinction due to the reddening of E(B-V) = 0.53
in the direction of the burst (Schlegel et al. 1998).
The photometry is based on USNO-b1 stars.


GRB_name: GRB160321A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19211
SUBJECT: GRB 160321A: Swift detection of a probable burst
DATE:    16/03/21 16:11:48 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

M. Stamatikos (OSU/NASA/GSFC), S. D. Barthelmy (GSFC),
A. A. Breeveld (UCL-MSSL), D. N. Burrows (PSU), S. B. Cenko (GSFC),
P. D'Avanzo (INAF-OAB), P.A. Evans (U Leicester), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA), N. P. M. Kuin (UCL-MSSL),
L. M. McCauley (PSU), A. Melandri (INAF-OAB), B. Mingo (U Leicester),
K. L. Page (U Leicester), T. G. R. Roegiers (PSU), T. Sakamoto (AGU),
B. Sbarufatti (INAF-OAB/PSU) and M. H. Siegel (PSU) report on behalf
of the Swift Team:

At 15:55:27 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160321A (trigger=680017).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 99.414, +5.715, which is 
   RA(J2000)  =  06h 37m 39s
   Dec(J2000) = +05d 42' 53"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a few weak peaks
with a total duration of about 35 sec.  The peak count rate
was ~700 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 15:57:18.0 UT, 110.9 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 99.4192,
5.7474 which is equivalent to:
   RA(J2000)  = 06h 37m 40.60s
   Dec(J2000) = +05d 44' 50.8"
with an uncertainty of 2.3 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 consistent with the Galactic value of 7.16
x 10^21 cm^-2 (Willingale et al. 2013). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 114 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 none of
the XRT error circle. 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 large, but
uncertain extinction expected. 

Due to the proximity of the source to the Galactic plane
(lat = -0.43 degrees) we cannot determine whether this is a
Galactic source or a GRB, based on the immediately available data. 

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: GRB160321A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19212
SUBJECT: GRB 160321A: MASTER observations zero Galaxy latitude GRB
DATE:    16/03/21 17:01:43 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,  V.Kornilov, D.Kuvshinov, N.Tyurina, P.Balanutsa, 
A.Kuznetsov, V.V.Chazov
Lomonosov Moscow State University,
Sternberg Astronomical Institute, Moscow State University

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

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

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 Kislovodsk was pointed to the  GRB160321A 6 sec after notice 
time and 68 sec after trigger time at 2016-03-21 15:56:35 UT. We do not 
found optical transient within SWIFT error-box 
(Stamatikos et al., GCN 60321A) brighter then 13.1.
After Sunset we found:


Pro.type Date time       Exp.time Limit Filt. Tube.
Alert        2016-03-21 16:43:44 180 18.6 W WEST
Alert        2016-03-21 16:43:44 180 18.1 W EAST
Alert        2016-03-21 16:40:18 180 18.6 W WEST
Alert        2016-03-21 16:36:45 180 18.6 W WEST
Alert        2016-03-21 16:36:45 180 18.1 W EAST
Alert        2016-03-21 16:33:16 180 18.5 W WEST
Alert        2016-03-21 16:28:25 180 17.6 P WEST
Alert        2016-03-21 16:28:25 180 17.6 P EAST
Alert        2016-03-21 16:21:39 180 17.4 P EAST

The galaxy latitude is about zero. So this is the optical free GRB.


The message may be cited.


GRB_name: GRB160321A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19213
SUBJECT: GRB 160321A: Enhanced Swift-XRT position
DATE:    16/03/21 22:10:03 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 1066 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 160321A, 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 = 99.41970, +5.74771 which is equivalent
to:

RA (J2000): 06h 37m 40.73s
Dec (J2000): +05d 44' 51.8"

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: GRB160316A
Detection_method: CALET
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19214
SUBJECT: GRB 160316A: CALET Gamma-Ray Burst Monitor detection
DATE:    16/03/22 10:11:56 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto@phys.aoyama.ac.jp>

Y. Shimizu (Kanagawa U), A. Yoshida, T. Sakamoto, I. Takahashi, Y. Kawakubo, K. Senuma, 
M. Moriyama, Y. Yamada (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka, 
S. Ozawa, S. Torii (Waseda U), T. Tamura (Kanagawa U), W. Ishizaki (ICRR), M. L. Cherry (LSU), 
S. Ricciarini (U of Florence) P. S. Marrocchesi (U of Siena) 
and the CALET collaboration:

The long-duration GRB160316A (Fermi-GBM trigger #479828730; INTEGRAL-ACS trigger #7425) 
triggered the CALET Gamma-Ray Burst Monitor (CGBM) at 13:45:16.8 on 16 March 2016.  
The burst signal was detected by all CGBM instruments.  

The light curve of the SGM shows a single peak.  The emission starts at T0+8 sec, 
peaks at T0+10 sec and ends at T0+23 sec.  The T90 duration measured by the SGM data 
is 10 +- 1 sec (40-1000 keV). 

The CGBM data used in this analysis are provided by the Waseda CALET Operation Center 
located at the Waseda University.


GRB_name: GRB160321A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19215
SUBJECT: GRB 160321A: Swift-XRT refined Analysis
DATE:    16/03/22 13:09:34 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), C. Pagani (U. Leicester), A.P. Beardmore (U.
Leicester), P.A. Evans (U. Leicester) and M. Stamatikos report on
behalf of the Swift-XRT team:

We have analysed 8.9 ks of XRT data for GRB 160321A (Stamatikos et al.
GCN Circ. 19211), from 96 s to 58.6 ks after the  BAT trigger. The data
comprise 31 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 Beardmore
et al. (GCN Circ. 19213).

The light curve can be modelled with a power-law decay with a decay
index of alpha=2.36 (+0.13, -0.11).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.45 (+0.33, -0.30). The
best-fitting absorption column is  9.3 (+3.8, -2.1) x 10^21 cm^-2,
consistent with the Galactic value of 7.2 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 6.5 x 10^-11 (8.8 x
10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      9.3 (+3.8, -2.1) x 10^21 cm^-2
Galactic foreground: 7.2 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:      1.45 (+0.33, -0.30)

If the light curve continues to decay with a power-law decay index of
2.36, the count rate at T+24 hours will be 1.2 x 10^-6 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.0 x
10^-17 (1.1 x 10^-16) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00680017.

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


GRB_name: GRB160321A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19216
SUBJECT: GRB 160321A: Swift-BAT refined analysis
DATE:    16/03/22 14:47:19 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto@phys.aoyama.ac.jp>

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. 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 160321A (trigger #680017)
(Stamatikos, et al., GCN Circ. 19211).  The BAT ground-calculated position is
RA, Dec = 99.420, 5.753 deg which is
     RA(J2000)  =  06h 37m 40.7s
     Dec(J2000) = +05d 45' 09.3"
with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 96%.

The mask-weighted light curve shows a single-pulse structure that starts
at ~ T0-22 sec, peaks at ~ T+2 sec, and ends at ~ T+23 sec.
T90 (15-350 keV) is 33.6 +- 4.8 sec (estimated error including systematics).

The time-averaged spectrum from T-20.9 to T+19.0 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.89 +- 0.19.  The fluence in the 15-150 keV band is 5.3 +- 0.7 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+2.17 sec in the 15-150 keV band
is 0.5 +- 0.1 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

Based on the ground analysis result, this event is very likely a GRB.
However, given that it is on the Galactic Plane (lat = -0.43 deg.),
we cannot rule out a galactic origin.  We note that the BAT time averaged
spectrum is soft but still in the typical range for BAT GRBs.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/680017/BA/


GRB_name: GRB160321A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19217
SUBJECT: GRB 160321A: Swift/UVOT Upper Limits
DATE:    16/03/22 15:04:48 GMT
FROM:    Sam Emery at MSSL-UCL  <samuel.emery.15@ucl.ac.uk>

S.W.K. Emery (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 160321A
115 s after the BAT trigger (Stamatikos et al., GCN Circ. 19211).
No optical afterglow consistent with the XRT position
(Beardmore et al. GCN Circ. 19213)
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           115          265          147         >20.4
u_FC               273          523          246         >19.7
white              115         6458          546         >21.1
v                  603         6870          452         >19.5
b                  529         6253          255         >20.1
u                  273        12683          570         >20.1
w1                 652        12607         1141         >20.2
m2                 627        11700         1205         >20.1
w2                 579         6664          452         >19.7

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.75 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB160321A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19218
SUBJECT: GRB 160321A: Possible RATIR Optical and NIR Detections
DATE:    16/03/22 17:14:25 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), Ori Fox (STScI), J. Xavier
Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (GSFC/STScI),
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 160321A (Stamatikos, et al., GCN 19211) 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 2016/03 22.14 to 2016/03 22.29 UTC (11.32
to 15.08 hours after the BAT trigger), obtaining a total of 2.47 hours
exposure in the r and i bands and 0.82 hours exposure in the Z, Y, J, and H
bands.

For a source within the Swift-XRT error circle (Beardmore, et al., GCN
19213), in comparison with the USNO-B1 and 2MASS catalogs, we obtain the
following weak detections and upper limits (3-sigma):

 r > 23.84
 i = 22.32 +/- 0.11
 Z = 22.49 +/- 0.34
 Y > 22.19
 J > 21.53
 H > 21.27

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

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


GRB_name: GRB160321A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19219
SUBJECT: GRB 160321A: AbAO optical observations
DATE:    16/03/22 20:25:03 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

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

We observed the field of Swift GRB 160321A (Stamatikos et al., GCN 
19211) with AS-32 (0.7m) telescope of Abastumani Observatory starting on 
Mar. 21 (UT) 16:26:45. We obtained several unfiltered images of the 
field. We do not detect any source within enhanced XRT error circle 
(Beardmore et al., GCN 19213) down to 21.9m. A probable source (S/N = 2) 
detected 3.5 arcsec South from the center of XRT error circle (Beardmore 
et al., GCN 19213) in coordinates (J2000) 06:37:40.74 +05:44:48.2 +/- 
0.5 arcsec in both coordinates.

Preliminary photometry of the field is following


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

2016-03-21 16:26:45   0.06839  none    41*120  21.9

Photometry is based on nearby USNO-B1.0 stars
USNO-B1_id   R2
0956-0104166 16.23
0957-0105913 15.38
0957-0106394 14.58
0956-0104566 15.41


GRB_name: GRB160325A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19222
SUBJECT: GRB 160325A: Swift detection of a burst
DATE:    16/03/25 07:31:21 GMT
FROM:    Kim Page at U.of Leicester  <klp5@leicester.ac.uk>

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

At 07:00:03 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160325A (trigger=680436).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 15.597, -72.706 which is 
   RA(J2000) = 01h 02m 23s
   Dec(J2000) = -72d 42' 22"
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 about 80 sec. One of the major pulses occurred 
at ~ -40 s before BAT trigger during spacecraft slews. The peak count rate
was ~9000 counts/sec (15-350 keV), at ~3 sec after the trigger. 

The XRT began observing the field at 07:01:10.0 UT, 66.4 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source located at RA, Dec 15.65210,
-72.69671 which is equivalent to:
   RA(J2000)  = 01h 02m 36.50s
   Dec(J2000) = -72d 41' 48.2"
with an uncertainty of 3.6 arcseconds (radius, 90% containment). This
location is 67 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 (5.91 x
10^21 cm^-2, Willingale et al. 2013), with an excess column of 2.3
(+2.60/-2.22) x 10^21 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 4.15e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 74 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. Because of the density of catalogued stars, further
analysis is required to report an upper limit for any afterglow in the
sub-image. The 8'x8' region for the list of sources generated on-board covers
0.00% of the XRT error circle. No correction has been made for the expected
extinction corresponding to E(B-V) of 0.04. 

Burst Advocate for this burst is E. Sonbas (edasonbas AT yahoo.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: GRB160325A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19223
SUBJECT: GRB160325A: REM NIR observations
DATE:    16/03/25 08:04:34 GMT
FROM:    Dino Fugazza at INAF-OAB  <dino.fugazza@brera.inaf.it>

D. Fugazza, A. Melandri (INAF/OAB) report on behalf of the REM team:

We observed the field of GRB 160325A (Sonbas et al., GCN 19222) with the 
60-cm robotic telescope REM located at the La Silla Observatory (Chile).
The observations started at 07:01:08 UT, 65 seconds after the Burst, and 
were carried out simultaneously with in the g, r, i, z and H bands.
An uncatalogued bright source in the XRT error box is detected at the 
coordinates:

RA(2000) =   01:02:36.06
Dec(2000) = -72:41:47.7

with an estimated uncertainty of +/- 0.7 arcsec.
A very preliminary photometry indicates it was H ~10.71 +/- 0.01 about 
270 sec after the burst.

Further observations are in progress to assess its variability.


GRB_name: GRB160325A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19224
SUBJECT: GRB 160325A: Fermi GBM detection
DATE:    16/03/25 12:53:53 GMT
FROM:    Oliver Roberts at UCD/Fermi  <oliver.roberts@ucd.ie>

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

"At 06:59:21.51 UT on the 25th of March 2016, the Fermi
Gamma-Ray Burst Monitor triggered and located GRB 160325A
(trigger 480581965 / 160325291), which was also detected by
Swift (Sonbas et al. 2008, GCN 19222). 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 XRT position is about 6 degrees.

The GBM light curve consists of two main emission episodes with a
duration (T90) of about 43 s (50-300 keV). The time-averaged
spectrum from T0+2.3 s to T0+45.3 s is well fit by a Band function
with Epeak = 235 +/- 19 keV, alpha = -0.78 +/- 0.05,
and beta = -2.21 +/- 0.14.

The event fluence (10-1000 keV) in this time interval is
(1.91 +/- 0.04) E-05 erg/cm^2. The 1.024-sec peak photon
flux measured starting from T0+9.5 s in the 10-1000 keV band
is 8.5 +/- 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: GRB160325A
Detection_method: Fermi LAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19227
SUBJECT: GRB 160325A: Fermi-LAT detection
DATE:    16/03/25 13:58:49 GMT
FROM:    Magnus Axelsson at Stockholm U.  <magaxe@kth.se>

M. Axelsson (KTH Stockholm), E. Bissaldi (Politecnico and INFN Bari), R. Desiante (INFN Torino and Udine University) and F. Longo (University of Trieste and INFN Trieste) report on behalf of the Fermi-LAT team:

At UT 06:59:21 on March 25 2016 Fermi-LAT detected high-energy emission from GRB 160325A, which was also detected by Swift (Sonbas et al. 2016, GCN 19222) and Fermi-GBM (trigger 480581965/160325291; Roberts 2016, GCN 19224).

The best LAT on-ground location is found to be:
RA, Dec (J2000) =  (16.14, -72.66)
with an error radius of 0.17 deg (90 % containment, statistical error only).

The Fermi-LAT position is consistent with that found by Swift-XRT (Sonbas et al. 2016, GCN 19222).

The LAT data show a significant increase in the event rate that is spatially and temporally correlated with the trigger with high significance. More than 45 photons >100 MeV and 3 photons > 1GeV are detected in the 1500 s following the trigger. The highest-energy photon is a 3 GeV  event which is observed 100 seconds after the GBM trigger.

The Fermi-LAT point of contact for this burst is M. Axelsson (magaxe@kth.se<mailto:magaxe@kth.se>).

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: GRB160325A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19228
SUBJECT: GRB160325A Swift/UVOT Detection
DATE:    16/03/25 15:25:24 GMT
FROM:    Marissa McCaule at PSU  <marissamc@swift.psu.edu>

L. M. McCauley (PSU) and E. Sonbas (Adiyaman Univ.) report on behalf of
the Swift/UVOT team:

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 74 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =        01:02:36.28 =  15.65118
  DEC(J2000) = -72:41:46.8  = -72.69634
with a 90%-confidence error radius of about 0.61 arc sec. This position is
5.35
arc sec. from the center of the XRT error circle and consistent with the
position
 reported by Fugazza et al. (GCN Circ. 19223).

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              74          160          86           15.48+-0.03

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: GRB160325A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19229
SUBJECT: GRB 160325A: Enhanced Swift-XRT position
DATE:    16/03/25 17:07:26 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 2264 s of XRT Photon Counting mode data and 3 UVOT
images for GRB 160325A, 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 = 15.65055, -72.69659 which is equivalent
to:

RA (J2000): 01h 02m 36.13s
Dec (J2000): -72d 41' 47.7"

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: GRB160325A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19230
SUBJECT: GRB 160325A: afterglow confirmation
DATE:    16/03/25 17:22:35 GMT
FROM:    Andrea Melandri at INAF-OAB  <andrea.melandri@brera.inaf.it>

A. Melandri, D. Fugazza (INAF-OAB), M. De Pasquale (MSSL-UCL)  report on behalf of a larger collaboration:

Further analysis of REM near-infrared observations of the field of of GRB 160325A (Sonbas et al., GCN 19222) showed that the source reported as candidate afterglow in our earlier imaging (Fugazza & Melandri, GCN 19223; McCauley & Sonbas, GCN 19228) has faded in the JHK filters. Observations cover the time interval bewteen ~1 and 120 minutes after the burst event.

The light curve has an initial decay of alpha1 ~ 0.45, and after 10 minutes it steepens to alpha2 ~ 1.5. The fading nature confirms that this source is the afterglow of GRB 160325A.


GRB_name: GRB160325A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19231
SUBJECT: GRB 160325A: Further Swift/UVOT Observations
DATE:    16/03/25 22:40:00 GMT
FROM:    Lea Hagen at PSU  <lea.zernow.hagen@gmail.com>

L. M. Z. Hagen (PSU) and E. Sonbas (Adiyaman Univ.)
report on behalf of the Swift/UVOT team:

We report further on the Swift/UVOT observations of GRB 160325A which
began 75 s after the BAT trigger (Sonbas et al., GCN Circ. 19222). A
source was reported earlier by McCauley et al. (GCN Circ. 19228), which
was consistent with the XRT position (Evans et al., GCN Circ. 19229)
and infrared detection (Fugazza et al., GCN Circ. 19223).  We confirm
that the source is rapidly fading.

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               75          224          146         15.65+-0.05
white              567         1187          205         17.24+-0.05
white             7227        12203          231         19.59+-0.16
v                  617          809           38         15.12+-0.07
v                 1044         1237           38         15.79+-0.10
v                 1392         6402          216         17.73+-0.14
b                  543          735           38         17.11+-0.11
b                 1143         1510           58         18.70+-0.33
b                 7023         7222          196        >19.64
u                  287          537          245         18.91+-0.22
u                  691         7017          274        >19.47
uvw1               666         1461           97         18.36+-0.32
uvw1              6613         6812          196         19.05+-0.33
uvm2               641         1263           77         18.30+-0.34
uvm2              1416         6607          216         18.73+-0.29
uvw2               593         1387           97        >18.63
uvw2              5998         6197          196         18.30+-0.19

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: GRB160325A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19232
SUBJECT: GRB 160325A: Swift-XRT refined Analysis
DATE:    16/03/25 23:14:54 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), A.P. Beardmore (U.
Leicester), P.A. Evans (U. Leicester), S.L. Gibson (U. Leicester), V.
D'Elia (ASDC) and E. Sonbas report on behalf of the Swift-XRT team:

We have analysed 7.5 ks of XRT data for GRB 160325A (Sonbas et al. GCN
Circ. 19222), from 55 s to 41.2 ks after the  BAT trigger. The data
comprise 436 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. 19229).

The late-time light curve (from T0+6.0 ks) can be modelled with a
power-law decay with a decay index of alpha=2.7 (+0.6, -0.5).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.342 (+0.033, -0.029). The
best-fitting absorption column is  consistent with the Galactic value
of 5.9 x 10^21 cm^-2 (Willingale et al. 2013). The PC mode spectrum has
a photon index of 2.18 (+0.16, -0.08) and a best-fitting absorption
column consistent with the Galactic value. The counts to observed
(unabsorbed) 0.3-10 keV flux conversion factor deduced from this
spectrum  is 3.9 x 10^-11 (7.3 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      5.9 (+0.9, -0.0) x 10^21 cm^-2
Galactic foreground: 5.9 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:      2.18 (+0.16, -0.08)

If the light curve continues to decay with a power-law decay index of
2.7, the count rate at T+24 hours will be 1.5 x 10^-4 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.9 x
10^-15 (1.1 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/00680436.

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


GRB_name: GRB160325A
Detection_method: GROND
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19233
SUBJECT: GRB 160325A: GROND Upper Limits
DATE:    16/03/26 01:22:14 GMT
FROM:    Corentin Delvaux at MPE  <delvaux@mpe.mpg.de>

C. Delvaux (MPE Garching), D. A. Kann (TLS Tautenburg), F. Knust, and J. 
Greiner (both MPE Garching) report on behalf of the GROND team:

We observed the field of GRB 160325A (Swift trigger 680436; Sonbas et 
al., GCN #19222, Fermi GBM detection, Roberts, GCN #19924, Fermi LAT 
detection, Axelsson et al., GCN #19227) 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 23:29 UT on 25/03/2016, 16.5 hrs after the GRB 
trigger. They were performed at an average seeing of 1.7" and at an 
average airmass of 2.3.

We do not detect the source reported by Fugazza et Melandri (GCN #19223) 
down to the following magnitudes (in AB system):

g > 22.4 mag,
r > 22.5 mag,
i > 22.3 mag,
z > 22.4 mag,
J > 20.3 mag,
H > 19.8 mag, and
K > 18.5 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)=0.1 mag in 
the direction of the burst (Schlafly & Finkbeiner 2011).


GRB_name: GRB160325A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19234
SUBJECT: GRB 160325A, Swift-BAT refined analysis
DATE:    16/03/26 04:07:19 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@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),
D. M. Palmer (LANL), T. Sakamoto (AGU), E. Sonbas (Adiyaman Univ.),
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 160325A (trigger #680436)
(Sonbas et al., GCN Circ. 19222).  The BAT ground-calculated position is
RA, Dec = 15.697, -72.702 deg which is
  RA(J2000)  =  01h 02m 47.4s
  Dec(J2000) = -72d 42' 06.4"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 96%.

The mask-weighted light curve shows a multi-peaked structure that starts at
~ T-60 s and ends at ~T+60 s. The burst location came into the BAT FoV
at ~T-93 s during a preplanned slew, so there could be further burst activities
beforehand. The burst structure contains two main pulses. The first pulse starts
at ~T-60 s, peaks at ~ T-34 s, and ends at ~T-25 s. The second pulse starts
at ~T0, peaks at ~T+3 s, and ends ~T+5 s. T90 (15-350 keV) is 64.9 +- 14.7 sec
(estimated error including systematics).

The time-averaged spectrum from T-51.74 to T+60.45 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.27 +- 0.04.  The fluence in the 15-150 keV band is 7.1 +- 0.2 x 10^-06 erg/cm2.
The 1-sec peak photon flux measured from T-33.46 sec in the 15-150 keV band
is 5.2 +- 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/680436/BA/


GRB_name: GRB160327A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19235
SUBJECT: GRB 160327A: Swift detection of a burst
DATE:    16/03/27 09:35:51 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

J. L. Racusin (NASA/GSFC), A. P. Beardmore (U Leicester),
K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of
the Swift Team:

At 09:16:07 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160327A (trigger=680655).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 146.689, +54.017 which is 
   RA(J2000) = 09h 46m 45s
   Dec(J2000) = +54d 01' 00"
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 20 sec.  The peak count rate
was ~3000 counts/sec (15-350 keV), at ~4 sec after the trigger. 

The XRT began observing the field at 09:17:08.2 UT, 60.5 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source with an enhanced position: RA, Dec
146.7019, 54.0131 which is equivalent to:
   RA(J2000)  = 09h 46m 48.45s
   Dec(J2000) = +54d 00' 47.0"
with an uncertainty of 2.2 arcseconds (radius, 90% containment). This
location is 30 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 1.17
x 10^20 cm^-2 (Willingale et al. 2013). 

The initial flux in the 2.5 s image was 1.01e-09 erg cm^-2 s^-1 (0.2-10
keV). 

The prompt automatic UVOT analysis is not available at this time. 
However, there appears to be no credible afterglow candidate in the
initial data. 

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: GRB160327A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19236
SUBJECT: GRB 160327A: RATIR Optical and NIR Afterglow Detection
DATE:    16/03/27 11:52:25 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), Ori Fox
(STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara
(GSFC/STScI), 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), and Vicki Toy (UMD) report:

We observed the field of GRB 160327A (Racusin, et al., GCN 19235) 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 2016/03 27.39 to 2016/03 27.41 UTC (3.6
minutes to 0.58 hours after the BAT trigger), obtaining a total of 0.36
hours exposure in the r and i bands and 0.15 hours exposure in the Z, Y, J,
and H bands.

For a source within the Swift-XRT error circle, in comparison with the SDSS
DR9 and 2MASS catalogs, we obtain the following detections:

r    21.78 +/- 0.13
i    19.68 +/- 0.02
Z   18.55 +/- 0.02
Y   17.75 +/- 0.01
J    17.56 +/- 0.01
H   16.74 +/- 0.01

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 =
9:46:48.54, +54:0:46.4 (J2000, +/-0.5").

Further observations are planned.

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


GRB_name: GRB160327A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19237
SUBJECT: GRB 160327A: Enhanced Swift-XRT position
DATE:    16/03/27 12:23:41 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 1040 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 160327A, 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 = 146.70264, +54.01278 which is equivalent
to:

RA (J2000): 09h 46m 48.63s
Dec (J2000): +54d 00' 46.0"

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: GRB160327A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19238
SUBJECT: GRB 160327A: Swift-XRT refined Analysis
DATE:    16/03/27 20:13:31 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), P.A. Evans (U. Leicester), S.L. Gibson (U.
Leicester), J.P. Osborne (U. Leicester), V. D'Elia (ASDC), A. D'Ai
(INAF-IASFPA) and J.L. Racusin report on behalf of the Swift-XRT team:

We have analysed 6.0 ks of XRT data for GRB 160327A (Racusin et al. GCN
Circ. 19235), from 51 s to 22.1 ks after the  BAT trigger. The data
comprise 7 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 Goad et al. (GCN Circ. 19237).

The light curve can be modelled with an initial power-law decay with an
index of alpha=2.53 (+0.14, -0.13), followed by a break at T+291 s to
an alpha of 0.59 (+/-0.06).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.97 (+0.15, -0.09). The
best-fitting absorption column is  consistent with the Galactic value
of 1.2 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has
a photon index of 1.90 (+0.16, -0.15) and a best-fitting absorption
column of 4.2 (+3.5, -3.0) x 10^20 cm^-2. The counts to observed
(unabsorbed) 0.3-10 keV flux conversion factor deduced from this
spectrum  is 3.4 x 10^-11 (3.7 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      4.2 (+3.5, -3.0) x 10^20 cm^-2
Galactic foreground: 1.2 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:      1.90 (+0.16, -0.15)

If the light curve continues to decay with a power-law decay index of
0.59, the count rate at T+24 hours will be 0.023 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.7 x
10^-13 (8.5 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/00680655.

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


GRB_name: GRB160327A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19239
SUBJECT: GRB 160327A: Swift/UVOT Upper Limits
DATE:    16/03/28 13:55:52 GMT
FROM:    Marissa McCaule at PSU  <marissamc@swift.psu.edu>

L. M. McCauley (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 160327A
71 s after the BAT trigger (Racusin et al., GCN Circ. 19235).
No optical afterglow consistent with the XRT position
(Goad et al. GCN Circ. 19237) 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               71         221         147      >21.06
u_FC                  284         534         246      >20.52
white                  71        5902         535      >21.50
v                     613        6310         451      >19.66
b                     539        5702         254      >20.38
u                     283        6918         670      >20.66
uvw1                  662        6721         412      >20.21
uvm2                  637        1088          58      >18.49
uvw2                  589        1039          38      >18.61


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).


GRB_name: GRB160327A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19240
SUBJECT: GRB 160327A: Swift-BAT refined analysis
DATE:    16/03/28 14:30:02 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), J. L. Racusin (NASA/GSFC)
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 160327A (trigger #680655) (Racusin, et al.,
GCN Circ. 19235). The BAT ground-calculated position is
RA, Dec = 146.698, 54.018 deg which is
   RA(J2000)  =  09h 46m 47.5s
   Dec(J2000) = +54d 01' 04.0"
with an uncertainty of 1.0 arcmin, (radius, sys+stat,
90% containment). The partial coding was 82%.

BAT light curve shows a single peak starting around
T-10 sec, peaking around T+5 sec and ending around
T+22 sec. T90 (15-350 keV) is 28 +- 9 sec (estimated
error including systematics).

The time-averaged spectrum from T-6.30 to T+42.80 sec
is best fit by a simple power-law model.  The power
law index of the time-averaged spectrum is 1.84 +- 0.11.
The fluence in the 15-150 keV band is
1.4 +- 0.1 x 10^-06 erg/cm2. The 1-sec peak photon flux
measured from T+4.14 sec in the 15-150 keV band
is 1.8 +- 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/680655/BA/


GRB_name: GRB160327A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19241
SUBJECT: GRB 160327A: Mondy optical upper limit
DATE:    16/03/28 15:43:01 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

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

We observed the field of the GRB 160327A (Racusin et al., GCN  19235) 
with AZT-33IK telescope of Sayan observatory (Mondy)  starting on March, 
27 (UT) 13:48:49.  We do not detect any source within enhanced Swift-XRT 
position (Goad et al., GCN 19237). In particular we do not detect the 
source reported in GCN 19236 and it could confirm the source (Zach 
Golkhou et al., GCN 19236) is an afterglow of the  GRB 160327A. 
Preliminary photometry  of  the combined image is following

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

2016-03-27  13:48:49  0.20675  R       25*120  23.0


Photometry is based on nearby SDSS-DR9 stars, Lupton transformations 
into R.


GRB_name: GRB160327A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19242
SUBJECT: GRB 160327A: KAIT optical afterglow confirmation
DATE:    16/03/28 19:36:40 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 151027A (Racusin et al.,
GCN 19235) starting at 09:17:37 UT, 90 s after the burst under
fair condition. 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 afterglow reported by Golkhou et al. (GCN 19236) was not detected
in any of our single images, however, it is detected in the
co-added images in both clear and I band, except V band. We report
the follow detection magnitude or upper limit:

Filter   co-add      Mid-time  Detection_Mag    Upper_limit
       
clear    20s x 10     549s      19.8 +/- 0.3    -
clear    20s x 10    1495s      20.2 +/- 0.4    -
clear    20s x 10    2162s            -         20.0
I        20s x 10     615s      18.1 +/- 0.2    -
I        20s x 10    1541s      18.8 +/- 0.4    -
I        20s x 10    2195s            -         18.7
V        20s x 15     781s            -         18.9

[GCN OPS NOTE(30mar16): Per author's request, the second reference
was changed from Zach to Golkhou.]


GRB_name: GRB160327A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19243
SUBJECT: GRB 160327A: Continued RATIR Optical and NIR Observations
DATE:    16/03/28 20:27:50 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), Ori Fox
(STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara
(GSFC/STScI), 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), and Vicki Toy (UMD) report:

We observed the field of GRB 160327A (Racusin, et al., GCN 19235) 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 2016/03 28.14 to 2016/03 28.39 UTC (17.98 to
24.15 hours after the BAT trigger), obtaining a total of 4.21 hours
exposure in the r and i bands and 1.76 hours exposure in the Z, Y, J, and H
bands.

For a source within the Swift-XRT error circle (Goad, et al., GCN 19237),
in comparison with the SDSS DR9 and 2MASS catalogs, we obtain the following
detections:

  r 23.84 +/- 0.22
  i 23.29 +/- 0.14
  Z 22.57 +/- 0.20
  Y 22.83 +/- 0.35
  J 22.43 +/- 0.29
  H 21.75 +/- 0.23

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
(Golkhou et al., GCN 19236), the source flux has decayed substantially in
all bands. The source r - i color changes from 2.1 +/- 0.1 to 0.6 +/-
0.3 between our first and the second night observations. The strong color
change suggests the possibility of contamination by the GRB host galaxy at
late-time.

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


GRB_name: GRB160325A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19244
SUBJECT: Konus-Wind observation of GRB 160325A
DATE:    16/03/29 13:44:26 GMT
FROM:    Anastasia Tsvetkova at Ioffe Institute  <tsvetkova@mail.ioffe.ru>

A. Tsvetkova, S. Golenetskii, R.Aptekar, D. Frederiks, P. Oleynik,
M. Ulanov, D. Svinkin, A. Lysenko, A. Kozlova and T. Cline
on behalf of the Konus-Wind team, report:

The long-duration GRB 160325A
(Swift-BAT trigger #680436: Sonbas, Lien & Page, GCN 19222;
Fermi GBM detection: Roberts, GCN 19224;
Fermi-LAT detection: Axelsson et al., GCN 19227)
triggered Konus-Wind at T0=25162.835 s UT (06:59:22.835).

The burst light curve shows two emission episodes,
a total duration of the burst (80-360 keV) is ~45 s.
The emission is seen up to ~1.5 MeV.

As observed by Konus-Wind, the burst
had a fluence of 1.73(-0.12,+0.14)x10^-5 erg/cm2,
and a 64-ms peak energy flux, measured from T0+10.304 s,
of 3.04(-1.04,+1.08)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+49.408 s)
is best fit in the 20 keV - 1.5 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.93(-0.14,+0.15),
and Ep = 214(-23,+31) keV (chi2 = 69/60 dof).
Fitting by the GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index:
beta < -2.45 (chi2 = 69/59 dof).

The spectrum near the peak count rate
(measured from T0 to T0+16.640 s)
is best fit in the 20 keV - 2 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.76(-0.15,+0.18),
the high energy photon index beta = -2.47(-0.59,+0.26),
the peak energy Ep = 207(-26,+32) keV,
chi2 = 70/57 dof.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB160325_T25162/

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


GRB_name: GRB160327A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19245
SUBJECT: GRB 160327A: Imaging and spectroscopy from GTC
DATE:    16/03/29 18:18:21 GMT
FROM:    Antonio de Ugarte Postigo at IAA-CSIC  <deugarte@iaa.es>

A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), N.R. Tanvir (U. Leicester), 
Z. Cano (U. Iceland), L. Izzo (U. Roma1), J.P.U. Fynbo (DARK/NBI), 
R. Sanchez-Ramirez (IAA-CSIC), C.C. Thoene (IAA-CSIC), P. Pesev 
(GRANTECAN, IAC, ULL) report:

We observed the field of GRB 160327A (Racusin, et al., GCN 19235) with 
OSIRIS mounted on the 10.4 m GTC telescope, located at Roque de los 
Muchachos Observatory (La Palma, Spain) starting at 00:26 UT on 28th 
March 2016 (15.17 hr after the burst).

In the acquisition image, we identify the afterglow proposed by Golkhou 
et al. (GCN 19236) and later also observed by Zheng & Filippenko (GCN 
19242). At the time of our observation, the object was at a magnitude 
of i(AB) = 23.89 +/-0.12 (as compared to nearby SDSS stars), with 
coordinates of (J2000, +/-0.5"):

R.A.: 09:46:48.56
Dec.: +54:00:46.3

We also note the presence of two other sources within 2.5â€ of the GRB 
afterglow: The first one is located at 09:46:48.35, +54:00:47.8 and has a 
magnitude of i(AB) = 23.76+/-0.11, and the second one is at 09:46:48.55, 
+54:00:44.2 with a magnitude of i(AB) = 24.24+/-0.15. We suspect that 
these sources may be contributing to the magnitudes given by Golkhou 
et al. (GCN 19243), especially in the bluer bands.

Spectroscopy of the GRB afterglow and the first of the two other objects 
was obtained by exposing 3x1200 s with grism R1000R, which covers 
between 5100 and 10100 Angstrom. We detect a trace of the GRB 
afterglow above 7300 AA, below which the emission drops abruptly. The 
other object shows a continuum over the complete spectral range, 
suggesting that this object is unrelated to the GRB. The afterglow 
spectrum is indicative of a Lyman-alpha drop at a redshift between 4.90 
and 5.01, with a most probable value at z = 4.99, although even lower 
redshifts could not be discarded for unusually large Hydrogen column 
densities. Due to the low S/N of the spectrum we are not able to confirm 
any other absorption lines at this time.


GRB_name: GRB160327A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19246
SUBJECT: GRB 160327A: JCMT SCUBA-2 sub-mm observation
DATE:    16/03/29 19:28:48 GMT
FROM:    Ian Smith at Rice U  <ian@spacsun.rice.edu>

I.A. Smith (Rice U.), N.R. Tanvir (U. of Leicester), and Y. Urata (NCU) 
report:

We observed the location of GRB 160327A (Racusin et al., GCN Circ. 19235) 
using the SCUBA-2 sub-millimeter continuum camera on the James Clerk 
Maxwell Telescope.  The observation started at 10:24 UT on 2016-03-27, 
corresponding to 68 minutes after the burst trigger.  Exposures totaling 
1.0 hours were made in good weather conditions.  No source was detected, 
with the RMS background noise being 2.0 mJy/beam at 850 microns and 
26.0 mJy/beam at 450 microns.

We thank Callie Matulonis and Iain Coulson for the prompt support of 
these observations that were taken under project M16AP005.


GRB_name: GRB160327A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19247
SUBJECT: GRB 160327A:  Early RAPTOR Limits
DATE:    16/03/29 22:58:53 GMT
FROM:    James Wren at LANL  <jwren@lanl.gov>

J. Wren, W.T. Vestrand, P. Wozniak, and H. Davis,

of Los Alamos National Laboratory report:


The RAPTOR network of robotic optical telescops made observations of Swift

trigger 680655 (Racusin, et al., GCN 19235).  Our Raptor-S telescope began

imaging at 09:16:27.58 UT, 19.9 s after the Swift trigger time.  We do not

detect the optical counterpart reported by RATIR (Golkhou, et al., GCN 19236).

We derive the following 3-sigma limits for our unfiltered observations based

on comparison to the USNO-B1.0 catalog R-band.


t-mid(s)   exp(s)    mag_limit

-------------------------------

32.5       5         17.4

67.8       40        18.6

131.8      10        18.0

180.4      100       19.2

249.9      200       19.6


GRB_name: GRB160324A
Detection_method: CALET
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19248
SUBJECT: GRB 160324A: CALET Gamma-Ray Burst Monitor detection
DATE:    16/03/29 23:43:36 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto@phys.aoyama.ac.jp>

T. Tamura (Kanagawa U), A. Yoshida, T. Sakamoto, I. Takahashi, Y. Kawakubo, 
K. Senuma, M. Moriyama, Y. Yamada (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), 
Y. Asaoka, S. Ozawa, S. Torii (Waseda U), Y. Shimizu (Kanagawa U), W. Ishizaki (ICRR), 
M. L. Cherry (LSU), S. Ricciarini (U of Florence) P. S. Marrocchesi (U of Siena) 
and the CALET collaboration:

The long-duration GRB 160324A (INTEGRAL-ACS trigger #7431; Konus-Wind trigger time on 
15:58:32.877 UT) triggered the CALET Gamma-Ray Burst Monitor (CGBM) at 15:58:38.0 on 
24 March 2016.  No real time CGBM GCN notice was distributed about this trigger because 
the real time communication from the ISS was off (loss of signal) between 15:51 and 16:13.  
The burst signal was seen by SGM instrument.

The light curve of the SGM shows at least two main episodes with a possible low level 
emission before the first episode.  The low-level emission starts at T0-30 sec.  The 
first episode starts at T0-5 sec, peaks at T0-3 sec and ends at T0+5 sec.  The second 
episode starts at T0+6 sec, peaks at T0+8sec and ends at T0+14 sec.  The T90 duration 
measured by the SGM data is 42 +- 2 sec (40-450 keV). 

The CGBM data used in this analysis are provided by the Waseda CALET Operation Center 
located at the Waseda University.


GRB_name: GRB160327A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19250
SUBJECT: GRB 160327A: Continued RATIR Optical and NIR Observations
DATE:    16/04/01 19:20:19 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), Ori Fox (STScI), J. Xavier
Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (GSFC/STScI),
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 160327A (Racusin, et al., GCN 19235) for a
third epoch 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 2016/04 1.22 to
2016/04 1.41 UTC (115.97 to 120.62 hours after the BAT trigger), obtaining
a total of 3.18 hours exposure in the r and i bands and 1.34 hours exposure
in the Z, Y, J, and H bands.

We are able to detect two of the three sources identified by the GTC (de
Ugarte Postigo, et al., GCN 19245).  The afterglow (GTC source #1 and
Golkhou, et al., GCN 19236) is detected in our night 2 observations on 28
March (Golkhou, et al., GCN 19243) but not on 1 April.  The GTC source #2
is detected on 28 March and 1 April and is the dominant source in terms of
brightness.  We do not detect GTC source #3 on either night.

In comparison with the SDSS DR9 and 2MASS catalogs, we obtain the following
detections and upper limits (3-sigma):

Afterglow (GTC Source #1):

 28 March                 1 April
r > 24.37               r > 24.41
i = 24.20 +/- 0.31      i > 24.38
Z = 22.98 +/- 0.28      Z > 23.15
Y > 22.85               Y > 22.91
J > 22.67               J > 22.61
H > 22.21               H > 22.23

GTC Source #2:

 28 March                 1 April
r = 23.84 +/- 0.22      r > 24.42
i = 23.33 +/- 0.14      i = 23.57 +/- 0.17
Z = 22.57 +/- 0.20      Z = 22.71 +/- 0.25
Y = 22.83 +/- 0.35      Y > 22.73
J = 22.43 +/- 0.29      J > 22.60
H = 21.75 +/- 0.24      H > 22.24

GTC Source #3:

 28 March                 1 April
r > 24.37               r > 24.41
i > 24.34               i > 24.39
Z > 23.19               Z > 23.11
Y > 22.86               Y > 22.76
J > 22.66               J > 22.6
H > 22.21               H > 22.25

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

In addition to our first night observations (Golkhou, et al., GCN 19236),
which show the afterglow peaking and then fading, our observations on 28
March and 1 April confirm the fading of the afterglow.  The above
photometric analysis, based on PSF fitting, may still suffer from modest
contamination between sources.  More detailed analyses are under way.

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


GRB_name: GRB160401A
Detection_method: INTEGRAL
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19251
SUBJECT: GRB 160401A: a long GRB detected by INTEGRAL
DATE:    16/04/01 21:32:32 GMT
FROM:    Sandro Mereghetti at IASF/CNR  <sandro@iasf-milano.inaf.it>

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

a gamma ray burst lasting about 130 s has been detected by IBAS in the 
IBIS/ISGRI data at 20:20:30 UT of April 1, 2016.

The refined coordinates (J2000) are:

R.A.=  89.7377  deg
DEC.=  26.6758  deg

with an uncertainty of 2 arcmin (90% c.l.).

The burst had a peak flux of 0.7 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: GRB160401A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19252
SUBJECT: GRB 160401A: MASTER-IAC prompt optical observations 
DATE:    16/04/01 22:07:26 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

R. Rebolo, M. Serra Ricart,  N. Lodieu, G. Israelian
The Instituto de Astrofisica de Canarias

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

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

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

V.Yurkov, Yu.Sergienko, A.Gabovich
Blagoveschensk Educational State University, Blagoveschensk

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)


MASTER-IAC  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in Teyde observatory was pointed to the  GRB160401.85 (Mereghetti 
et al., GCN 19251) 7 sec after 
notice time 
and 15 sec after trigger time at 2016-04-01 20:20:57 UT. On our first (10s 
exposure)  set we didn't find new optical transient within 
INTEGRAL error-box 
(ra=05 59 00 dec=+26 41 11 r=0.054) brighter then 16.3 (5-sigma upper 
limit).


The message may be cited.


GRB_name: GRB160401A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19253
SUBJECT: GRB 160401A: Swift ToO observations
DATE:    16/04/02 08:18:21 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 160401A. 
Automated analysis of the XRT data will be presented online at
http://www.swift.ac.uk/ToO_GRBs/00020603

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: GRB160401A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19254
SUBJECT: GRB 160401A: LT observations
DATE:    16/04/02 14:04:12 GMT
FROM:    Cristiano Guidorzi at Ferrara U,Italy  <guidorzi@fe.infn.it>

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

The 2-m Liverpool Telescope automatically began observing INTEGRAL GRB 
160401A (Mereghetti et al. GCN 19251) on April 01, 20:23:44 UT, i.e. 3.2 
minutes since the GRB trigger time. From the subtraction of two 3x10-s 
r-band frames taken at 46 and 68 minutes post GRB trigger we do not 
detect any uncatalogued, significantly variable object within the 
INTEGRAL error circle down to r~20 mag calibrated against nearby USNOB-1 
stars, in agreement with previous reports (Rebolo et al. GCN 19252).


GRB_name: GRB160401A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19255
SUBJECT: GRB 160401A: Zadko observatory - Gingin optical observations
DATE:    16/04/02 14:19:27 GMT
FROM:    Alain Klotz at IRAP-CNRS-OMP  <Alain.Klotz@free.fr>

Klotz A., Turpin D., Atteia J.L. (CNRS-OMP-IRAP),
Boer, M., Laugier, R. (CNRS-ARTEMIS),
Gendre B. (UVI - Etelman Obs.),
Coward, D. McPherson, D. Williams A., Martin R.,
Moore J., Dodson R. (UWA) report:

We imaged the field of GRB 160401A detected by Integral
(Mereghetti et al. GCNC 19251) with the Zadko robotic
telescope (D=100cm) located at the observatory - Gingin,
Australia.

The observations started 0.63 day after the GRB trigger
as soon as the night became. The elevation of the field
decreased from 27 degrees above horizon and weather
conditions were good.

We co-added a series of exposures. We did not observed
any new optical source than those in the SDSS in a radius of
2 arcmin centered ont the position RA=05:58:57 Dec=+26:40:33
J2000:

t1(d) t2(d)  Rmag_lim
0.63  0.66   19.0

Magnitudes were estimated with the nearby USNO-B1 stars
and are not corrected for galactic dust extinction.

N.B. Galactic coordinates are lon=183.4 lat= +1.4


GRB_name: GRB160401A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19256
SUBJECT: GRB 160401A: Swift/UVOT Upper Limits
DATE:    16/04/02 20:08:19 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

Paul Kuin (MSSL/UCL) and L.M. McCauley (PSU) report on behalf of the
Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 160401A
43ks s after the INTEGRAL trigger (Mereghetti et al., GCN Circ.19251).
No optical afterglow consistent with the INTEGRAL position is detected
in the initial UVOT exposures. The burst location was also observed by
MASTER-IAC (Rebolo et al., GCN Circ. no. 19252); LT (Guidorzi et al.
GCN Circ. no. 19254), and the Zadko observatory (Klotz et al. GCN
Circ. 19255); none of whom observed an afterglow.
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

white            43678        44209          522         >20.8
v                44509        45370          843         >19.5
u                42847        43671          811         >19.9

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 1.13 in the direction of the burst
(Schlegel et al. 1998).

[GCN OPS NOTE(02apr16):  The letter 'A' was added to the GRB name.]


GRB_name: GRB160401A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19257
SUBJECT: GRB 160401A: Swift-XRT observations
DATE:    16/04/03 15:29:59 GMT
FROM:    Marissa McCaule at PSU  <marissamc@swift.psu.edu>

L.M. McCauley (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU),
S.L. Gibson (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (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 INTEGRAL-detected
burst GRB 160401A (Mereghetti et al. GCN Circ. 19251), collecting 2.9
ks of Photon Counting (PC) mode data between T0+42.9 ks and T0+49.1 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 ~0.003
to ~0.005 ct s^-1, corresponding to a 0.3-10 keV observed flux of
1.3e-13 to 1.9e-13 erg cm^-2 s^-1 (assuming a typical GRB spectrum).

Four 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/00020603.

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


GRB_name: GRB160406A
Detection_method: IPN Triangulation
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19259
SUBJECT: IPN Triangulation of GRB 160406A (short/hard)
DATE:    16/04/07 21:02:59 GMT
FROM:    Anna Kozlova at Ioffe Institute  <ann_kozlova@mail.ioffe.ru>

A. Kozlova, S. Golenetskii, R. Aptekar, 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,

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

S. Barthelmy, J. Cummings, N. Gehrels, H. Krimm, and D. Palmer,
on behalf of the Swift-BAT team, report:

A short-duration GRB 160406A has been detected by Konus-Wind, Fermi (GBM;
trigger 481637080), Swift (BAT), and INTEGRAL (SPI-ACS), so far, at about
43477 s UT (12:04:37). 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:
  261.797 (17h 27m 11s) +32.363 (+32d 21' 48")
 Corners:
  262.805 (17h 31m 13s) +27.232 (+27d 13' 56")
  263.169 (17h 32m 41s) +27.080 (+27d 04' 47")
  260.364 (17h 21m 27s) +38.219 (+38d 13' 07")
  259.883 (17h 19m 32s) +38.538 (+38d 32' 15")
 ---------------------------------------------
The error box area is 3.34 sq. deg, and its maximum
dimension is 11.8 deg (the minimum one is 17.5 arcmin).
The Sun distance was 106 deg.

This box may be improved.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB160406_T43476/IPN/

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


GRB_name: GRB160408A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19260
SUBJECT: GRB 160408A: Swift detection of a short burst
DATE:    16/04/08 06:39:08 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

P.A. Evans (U Leicester), S. D. Barthelmy (GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU)
report on behalf of the Swift Team:

At 06:25:43 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160408A (trigger=682059).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 122.557, +71.140, which is 
   RA(J2000)  =  08h 10m 14s
   Dec(J2000) = +71d 08' 25"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a single spike
with a duration of about 0.5 sec.  The peak count rate
was ~5000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 06:27:18.5 UT, 94.8 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 122.6235, 71.1284 which
is equivalent to:
   RA(J2000)  = 08h 10m 29.64s
   Dec(J2000) = +71d 07' 42.3"
with an uncertainty of 2.2 arcseconds (radius, 90% containment). This
location is 87 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 (4.18 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 3.9
(+3.04/-2.61) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 98 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 none of
the XRT error circle. 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 0.03. 

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: GRB160408A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19261
SUBJECT: GRB 160408A: Enhanced Swift-XRT position
DATE:    16/04/08 09:58:51 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 1293 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 160408A, 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 = 122.62470, +71.12831 which is equivalent
to:

RA (J2000): 08h 10m 29.93s
Dec (J2000): +71d 07' 41.9"

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: GRB160408A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19262
SUBJECT: GRB 160408A: Gemini optical observations
DATE:    16/04/08 10:45:28 GMT
FROM:    Andrew Levan at U.of Leicester  <A.J.Levan@warwick.ac.uk>

A.J. Levan (U. Warwick) and N.R. Tanvir (U. Leicester) report for a larger collaboration: 

â€œWe observed the location of the short GRB 160408A (Evans et al. GCN 19260) with Gemini-North and GMOS. Observations were taken in the r-band, starting at 07:23 UT, approximately 58 minutes after the burst. Several objects are present in the field close to the refined XRT position (Osborne et al. GCN 19261). The closest objects are a compact source (A) and a more extended galaxy (B). The locations of these sources are: 

Source A: 
RA(J2000) 08h 10m 29.81s
DEC(J2000) 71d 07â€™ 43.7â€ 

Source B: 
RA(J2000) 08h 10m 29.32s
DEC(J2000) 71d 07â€™ 40.5â€

with an uncertainty of approximately 0.3â€ in each co-ordinate. Conditions were not photometric at the time of the observations, but comparison with USNO-B1 sources in the field of view suggests that source A has a magnitude of r~24.5, source B is approximately a magnitude brighter. 

We thank the Gemini staff for the rapid execution of these observations.â€œ


GRB_name: GRB160408A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19263
SUBJECT: GRB 160408A: Swift-BAT refined analysis
DATE:    16/04/08 13:13:33 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),
P.A. Evans (U Leicester), 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-120 to T+302 sec from the recent telemetry downlinks,
we report further analysis of BAT GRB 160408A (trigger #682059)
(Evans, et al., GCN Circ. 19260).  The BAT ground-calculated position is
RA, Dec = 122.561, 71.128 deg, which is 
   RA(J2000)  =  08h 10m 14.6s 
   Dec(J2000) = +71d 07' 40.0" 
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 33%.
 
The mask-weighted light curve starts at ~T0, peaks at ~T+0.1 sec, and
ends at ~T+0.4 sec.  T90 (15-350 keV) is 0.32 +- 0.04 sec
(estimated error including systematics).
 
The time-averaged spectrum from T+0.02 to T+0.37 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
0.85 +- 0.25.  The fluence in the 15-150 keV band is 1.6 +- 0.2 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-0.30 sec in the 15-150 keV band
is 2.1 +- 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/682059/BA/

We note that this burst was detected by Fermi-GBM, CALET-GBM, Swift-BAT,
and INTEGRAL-SPIACS.


GRB_name: GRB160406A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19264
SUBJECT: GRB 160406A: Fermi GBM observation
DATE:    16/04/08 14:23:18 GMT
FROM:    Andreas von Kienlin at MPE  <azk@mpe.mpg.de>

A. von Kienlin (MPE/UAH) and C. Meegan (UAH) 
report on behalf of the Fermi GBM Team: 

 "At 12:04:36.80 UT on 6 April 2016, the Fermi Gamma-Ray Burst Monitor
 triggered and located GRB 160406A (trigger 481637080 / 160406503), 
which was also detected by IPN (Kozlova et al. 2016, GCN 19259). The 
GBM on-ground location is consistent with the IPN triangulated position. 

The angle from the Fermi LAT boresight at the GBM trigger time is 77.5 degrees. 

The GBM light curve shows a single pulse 
with a duration (T90) of about 0.4 s (50-300 keV). 
The time-averaged spectrum from T0-0.064 s to T0+0.192 s is 
best fit by a power law function with an exponential 
high-energy cutoff. The power law index is -0.75 (+0.13/-0.12) and 
the cutoff energy, parameterized as Epeak, is 700 (+210 /-130) keV.

The event fluence (10-1000 keV) in this time interval is (7.2 +/- 0.4)E-07 erg/cm^2. 
The 0.064-sec peak photon flux measured starting from T0+0.0 s in the 10-1000 keV
band is 17 +/- 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: GRB160408A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19265
SUBJECT: GRB 160408A: Fermi GBM detection
DATE:    16/04/08 15:23:19 GMT
FROM:    Oliver Roberts at UCD/Fermi  <oliver.roberts@ucd.ie>

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

"At 06:25:43.86 UT on the 8th of April 2016, the Fermi
Gamma-Ray Burst Monitor triggered and located GRB 160408A
(trigger 481789547 / 160408268), which was also detected by
Swift (Evans et al. 2008, GCN 19620). 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 XRT position is about 7 degrees.

The GBM light curve consists of two bright, short emission
episodes, with a duration (T90) of about 0.9 s (50-300 keV).
The time-averaged spectrum from T0-0.064 s to T0+0.384 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -0.76 +/- 0.10 and
the cutoff energy, parameterized as Epeak, is 914 +/- 184 keV.

The event fluence (10-1000 keV) in this time interval is
(1.25 +/- 0.08)E-06 erg/cm^2. The 64 ms peak photon flux
measured starting from T0+0 s in the 10-1000 keV band,
is 12.4 +/- 1.4 ph/s/cm^2.

A Band function fits the spectrum equally well, with
Epeak = 765 +/- 198 keV, alpha = -0.70 +/- 0.12, and
beta = -2.27 +/- 0.41.

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


GRB_name: GRB160408A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19266
SUBJECT: GRB 160408A: Swift-XRT refined Analysis
DATE:    16/04/08 18:14:24 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), J.P. Osborne (U.
Leicester), K.L. Page (U. Leicester), C. Pagani (U. Leicester), A. D'Ai
(INAF-IASFPA), A. Maselli  (INAF-IASFPA), A. Melandri (INAF-OAB), D.N.
Burrows (PSU) and P.A. Evans report on behalf of the Swift-XRT team:

We have analysed 6.2 ks of XRT data for GRB 160408A (Evans et al. GCN
Circ. 19260), from 103 s to 23.4 ks after the  BAT trigger. The data
are entirely in Photon Counting (PC) mode. The enhanced XRT position
for this burst was given by Osborne et al. (GCN Circ. 19261).

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.3 (+/-0.3).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.1 (+/-0.4). The
best-fitting absorption column is  1.6 (+1.4, -1.1) x 10^21 cm^-2, in
excess of the Galactic value of 4.2 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 3.4 x 10^-11 (4.6 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      1.6 (+1.4, -1.1) x 10^21 cm^-2
Galactic foreground: 4.2 x 10^20 cm^-2
Excess significance: 1.9 sigma
Photon index:      2.1 (+/-0.4)

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 8.4 x 10^-5 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.8 x
10^-15 (3.8 x 10^-15) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00682059.

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


GRB_name: GRB160408A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19267
SUBJECT: GRB 160408A: Swift/UVOT Upper Limits
DATE:    16/04/08 20:15:45 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <siegel@swift.psu.edu>

M. H. Siegel (PSU) 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 160408A
98 s after the BAT trigger (Evans et al., GCN Circ. 19260).
No optical afterglow consistent with the XRT position
(Osborne et al. GCN Circ. 19261) or the possible
optical counterparts (Levan et al., GCN Circ. 19262)
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            98          248          147         >21.0
u_FC               311          561          246         >19.7
white               98         1365          373         >21.8
v                  641         1414           97         >19.4
b                  566         1340           78         >19.6
u                  311         1316          304         >19.9
w1                 691         1291           58         >19.5
m2                 838         1092           39         >18.8
w2                 617         1390           97         >19.9

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.03 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB160408A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19268
SUBJECT: GRB 160408A: TLS Tautenburg observations
DATE:    16/04/09 09:34:20 GMT
FROM:    Sebastian Schmidl at TLS Tautenburg  <schmidl@tls-tautenburg.de>

J. I. Avalos (University of Leipzig), N. P. Plaza (Universidad Autonoma de
Madrid), M. Blunck (University of Leipzig), L. Lalounta (University of
Patras), E. Komucyeya (Mbarara University), S. Schmidl, S. Klose, D. A.
Kann, A. Nicuesa Guelbenzu, and F. Ludwig (all TLS Tautenburg) report:

We observed the field of the short GRB 160408A (Evans et al., GCN
19260) with the Tautenburg 1.34-m Schmidt telescope at as mid-time of about
15.3 hrs after the GRB trigger, at a mean airmass of 1.2. We obtained 10 x
300 sec exposures in the Ic band.

Inside the 1".9 enhanced XRT error circle (Osborne et al.,GCN 19261),
we do not detect the possible optical counterparts reported by Levan et
al. (GCN Circ. 19262). We estimate a preliminary upper limit of Ic > 21.3
mag, calibrated against USNO-B1 field stars.

These observations were performed as part of the Tautenburg Observing
School at the Thueringer Landessternwarte.

[GCN OPS REPORT(14apr16):  Per author's request, the institutional affiliations
of the authors was corrected, and the last sentence was added.]


GRB_name: GRB160408A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19269
SUBJECT: GRB 160408A: Gemini afterglow confirmation
DATE:    16/04/09 15:04:49 GMT
FROM:    Andrew Levan at U.of Leicester  <A.J.Levan@warwick.ac.uk>

A.J. Levan (U. Warwick), N.R. Tanvir (U. Leicester), A. Cucchiara (GSFC/STScI), W. Fong (Arizona), D. Perley (DARK/NBI) report for a larger collaboration: 

â€œWe obtained a second epoch of Gemini-North observations of the short GRB 160408A (Evans et al. GCN 19260, Palmer et al. GCN 19263) on 9 April 2016, approximately 22 hours after our previous observations. Although the images are somewhat shallower than the first epoch, the previously identified source A (Levan & Tanvir GCN 19262) has clearly faded by at least a magnitude between the two epochs, and is not detected in our new imaging. This confirms it as the optical afterglow of GRB 160408A.â€


GRB_name: GRB160408A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19270
SUBJECT: GRB 160408A: GMG observation limit
DATE:    16/04/10 02:50:48 GMT
FROM:    Jirong Mao at Yunnan Obs  <jirongmao_obs@ynao.ac.cn>

W.-M. Yi, J. Mao and J.-M. Bai (YNAO) report:


We observed the field of GRB 160408A (Evans et al., GCN 19260) with the 2.4-meter optical telescope at Gao-Mei-Gu (GMG) 
station of Yunnan Observatories. Observations began from 15:10:26 UT, Apr. 8th, 2016, about 9 hours after the trigger. 
We did not detect any source at the afterglow position (Levan et al. GCN 19269) down to a limit of R~23.3 mag.


GRB_name: GRB160410A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19271
SUBJECT: GRB 160410A: Swift detection of a (possibly-short) burst with an optical counterpart
DATE:    16/04/10 05:35:57 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

S. L. Gibson (U Leicester), D. Malesani (DARK/NBI),
K. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU)
report on behalf of the Swift Team:

At 05:09:48 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160410A (trigger=682269).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 150.681, +3.443 which is 
   RA(J2000) = 10h 02m 43s
   Dec(J2000) = +03d 26' 37"
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 2 sec.  The peak count rate
was ~9000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 05:11:10.9 UT, 82.9 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 150.6857, 3.4782 which is equivalent to:
   RA(J2000)  = +10h 02m 44.57s
   Dec(J2000) = +03d 28' 41.5"
with an uncertainty of 5.6 arcseconds (radius, 90% containment). This
location is 127 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. 

The initial flux in the 2.5 s image was 1.04e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 91 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
 RA(J2000)  = 10:02:44.39 = 150.68494
 DEC(J2000) = +03:28:42.9  = 3.47858
with a 90%-confidence error radius of about 0.78 arc sec. This position is 3.0
arc sec. from the center of the XRT error circle. The estimated magnitude is
19.49 with a 1-sigma error of about  0.16. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.02. 

Burst Advocate for this burst is S. L. Gibson (slg44 AT 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: GRB160410A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19272
SUBJECT: GRB 160410A: GROND optical detection
DATE:    16/04/10 06:34:19 GMT
FROM:    Robert Yates at MPE/Swift  <robyates@mpe.mpg.de>

R Yates (MPE Garching) , T Kruehler (MPE Garching), J Greiner (MPE
Garching) report on behalf of the GROND team:

We observed the field of GRB 160410A (Swift trigger 682269; Gibson et al.,
GCN #19271) 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 05:42 UT on 10-04-2016, 32mins after the GRB
trigger. They were performed at an average seeing of 1.8" and at an
average airmass of 2.7.

We found a single point source within the 0.7" Swift-UVOT error circle
reported by Gibson et al. (GCN #19271) at

RA (J2000) = 10h 02m 44.37s

DEC (J2000) = +03d 28' 42.4"

with an uncertainty of 0.5" in each coordinate.

Based on the first 4 min of total exposures in g'r'i'z' and JHK, we
estimate preliminary magnitudes (all in AB system) of

g' = 20.6 +/- 0.1 mag,
r' = 20.5 +/- 0.1 mag,
i' = 20.7 +/- 0.1 mag,
z' = 20.5 +/- 0.2 mag,
J > 20.0 mag,
H > 19.6 mag, and
K > 18.0 mag.

Given magnitudes are calibrated against SDSS/2MASS 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)=0.0180 mag
in the direction of the burst (Schlafly & Finkbeiner 2011).


GRB_name: GRB160410A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19273
SUBJECT: GRB 160410A: Enhanced Swift-XRT position
DATE:    16/04/10 12:39:51 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 380 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 160410A, 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 = 150.68560, +3.47856 which is equivalent
to:

RA (J2000): 10h 02m 44.54s
Dec (J2000): +03d 28' 42.8"

with an uncertainty of 3.0 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: GRB160410A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19274
SUBJECT: GRB 160410A: VLT/X-shooter redshift
DATE:    16/04/10 15:50:03 GMT
FROM:    Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst  <malesani@dark-cosmology.dk>

J. Selsing (DARK/NBI), P.M. Vreeswijk (WIS), J. Japelj (INAF/OATs), V. 
D'Elia (ASI/ASDC and INAF/Roma), A. de Ugarte Postigo (IAA/CSIC and 
DARK/NBI), G. Pugliese (API/UvA), D. Xu (NAOC/CAS), D. Malesani 
(DARK/NBI), T. Kruehler (MPE), J.P.U. Fynbo (DARK/NBI), report on behalf 
of a larger collaboration:

We observed the optical afterglow of GRB 160410A (Gibson et al., GCN 
19271; Yates et al., GCN 19272) with the ESO Very Large Telescope UT2 
(Kueyen) equipped with X-shooter. Observations were triggered 
robotically in "rapid response mode" (RRM). Our spectroscopic 
integration started 8.4 min after the GRB and 3x600 s spectra were 
collected covering the wavelength range 3000-24,500 AA, until the target 
became too low on the horizon.

The optical afterglow is detected in our acquisition image (7.7 min 
after the GRB) with a magnitude r = 20.29 +- 0.06 (AB), calibrated 
against two nearby SDSS stars.

Our spectra reveal continuum over the entire spectral range redward of 
~3400 AA, which constrains the redshift to be z < 1.8. Besides, a number 
of weak absorption features are detected, which we interpret as due to 
Fe II and Al II at a redshift z = 1.717. At this redshift, the Mg II 
2796,2803 doublet lies into a region of strong telluric absorption (the 
A band) and is not detected. Two intervening C IV absorbers are also 
observed at z = 1.444 and z = 1.581.

We acknowledge excellent and prompt support from the ESO staff at 
Paranal, in particular Annalisa De Cia and Cedric Ledoux.


GRB_name: GRB160410A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19275
SUBJECT: GRB 160410A: Swift/UVOT Detection
DATE:    16/04/10 17:40:46 GMT
FROM:    Frank Marshall at GSFC  <femarsha@khamseen.gsfc.nasa.gov>

F. E. Marshall (NASA/GSFC) and S. L. Gibson (U. Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 160410A
91 s after the BAT trigger (Gibson et al., GCN Circ. 19271).
A source consistent with the initial UVOT position
(Gibson et al. GCN Circ. 19271), the enhanced XRT position
(Beardmore et al. GCN Circ. 19273), and the GROND position
(Yates et al. GCN Circ. 19272)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  10:02:44.37 = 150.68488 (deg.)
    Dec (J2000) = +03:28:42.7  =   3.47853 (deg.)
with an estimated uncertainty of 0.49 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               91          241          147         19.46 +/- 0.10
v                 4867         6503          393        >19.7
b                 4251         5887          393        >20.2
u                  304        12411          866         20.50 +/- 0.20
w1                5277        11801         1082        >20.3
m2                5072        10893         1082        >20.8
w2                4662         6298          393        >20.5

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: GRB160410A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19276
SUBJECT: GRB 160410A: Swift-BAT refined analysis of the short GRB
DATE:    16/04/10 17:41:10 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), S. L. Gibson (U Leicester), H. A. Krimm (GSFC/USRA),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), J. P. Norris (BSU),
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 short GRB 160410A (trigger #682269)
(Gibson, et al., GCN Circ. 19271).  The BAT ground-calculated position is
RA, Dec = 150.695, 3.461 deg, which is 
   RA(J2000)  =  10h 02m 46.9s 
   Dec(J2000) = +03d 27' 40.3" 
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 37%.
 
The mask-weighted light curve shows an initial spike starting at ~T-0.2 s
peaking at ~T+0.1 s with a decay out to ~T+2.5 s, then a greatly reduced
flux level portion out to ~T+9 s.  T90 (15-350 keV) is 8.2 +- 1.6 s
(estimated error including systematics).
 
The time-averaged spectrum from T+0.04 to T+9.60 s is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
0.93 +- 0.17.  The fluence in the 15-150 keV band is 7.8 +- 0.8 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.04 sec in the 15-150 keV band
is 3.5 +- 0.3 ph/cm2/s.  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/682269/BA/

Using a 4-ms binned light curve for this bright burst, the lag of the initial pulse
(~T0 to ~T0+2 s) for the 100-350 keV to 25-50 keV bands is -3 (+/-7) ms
(with 1-sigma error) and for the 50-100 kev to 15-25 keV bands the lag is 8 (+/-14) ms.
These values are consistant with zero, thus confirming that this is a short GRB.
There is extended emission out to ~T+10 sec at ~0.038 counts/det/sec then dropping
to ~0.0055 counts/det/sec out to ~T+92 sec.


GRB_name: GRB160410A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19277
SUBJECT: GRB 160410A: Skynet PROMPT-CTIO observations of the optical afterglow
DATE:    16/04/10 20:43:16 GMT
FROM:    Adam S. Trotter at UNC-Chapel Hill/PROMPT/Skynet  <atrotter@physics.unc.edu>

A. Trotter, D. Reichart, J. Haislip, J. Moore, N. Frank, M. Maples, E. Johnson, R. Joyner, J. Martin, C. Salemi, J. A. Crain, K. Ivarsen, A. LaCluyze, and M. Nysewander report:

Skynet observed the Swift BAT/XRT localization of GRB 160410A (Gibson et al., GCN 19271, Swift trigger=682269) with with one 16" telescope (P5), and two 24" telescopes (P1, P8) of the PROMPT array at CTIO, Chile. Starting at 2016-04-10 05:10:36 UT and continuing until 05:54 UT (t=48s-45m post-trigger), Skynet took a total of 93 exposures ranging from 5-160s in the I band (P1, P5) and the B band (P8).  

We detect a fading optical afterglow in individual and stacked I-band images at the position first reported by Gibson et al. (GCN 19271) and Yates et al. (GCN 19272), with I~17.3 at t=1m and I~19.4 at t=6m. 

A preliminary light curve is at:
http://www.skynet.unc.edu/grb/grb160410a.png

Magnitudes are in the Vega System, calibrated to 4 APASS DR9 stars in the field.  Magnitudes have not been corrected for line-of-sight Milky Way dust extinction, with expected E(B-V)=0.02 (Schlafly & Finkbeiner 2011).

No further Skynet observations are scheduled.


GRB_name: GRB160410A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19278
SUBJECT: GRB 160410A: Keck-I/LRIS redshift
DATE:    16/04/10 20:53:26 GMT
FROM:    Yi Cao at Caltech  <ycao@astro.caltech.edu>

Yi Cao, S. R. Kulkarni, Lin Yan, Vikram Ravi, H. K. Vedantham, Mansi M.
Kasliwal (Caltech)

We obtained a spectrum of the optical afterglow of GRB 160410A with the Low
Resolution Imaging Spectrometer (LRIS) on the Keck-I telescope at Mauna
Kea, following the Swift UVOT localization (GCN 19271). Our spectroscopic
integration started 84.25 minutes after the Swift trigger at airmass 1.05
and one 600s spectrum was obtained covering 3100-10200 Angstrom.

Our spectrum reveals a blue continuum superposed by a strong and broad
absorption around centered around 3300 Angstrom as well as a number of weak
and narrow absorption features. Upon obtaining the data we  determined a
redshift of 1.72  based primarily on the broad damped Lyman alpha and
threshold detection of narrow Si II, O I, C IV and Mg II absorption lines.
Our redshift is consistent to that derived from the VLT/X-shooter spectra
(GCN 19274).


GRB_name: GRB160411A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19279
SUBJECT: GRB 160411A: Swift detection of a short burst
DATE:    16/04/11 01:37:41 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

K. L. Page (U Leicester), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC),
D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the
Swift Team:

At 01:28:51 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160411A (trigger=682339).  Swift could not immediately
slew to the burst due to an observing constraint. 
The BAT on-board calculated location is 
RA, Dec 349.362, -40.271 which is 
   RA(J2000) = 23h 17m 27s
   Dec(J2000) = -40d 16' 14"
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 0.5 sec.  The peak count rate
was ~3000 counts/sec (15-350 keV), at ~0.2 sec after the trigger. 

Due to an observing constraint, Swift will not slew until T0+50.4
minutes. There will be no XRT or UVOT data until this time. 

Burst Advocate for this burst is K. L. Page (klp5 AT leicester.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: GRB160410A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19280
SUBJECT: GRB 160410A: GMG observation
DATE:    16/04/11 02:42:04 GMT
FROM:    Jirong Mao at Yunnan Obs  <jirongmao_obs@ynao.ac.cn>

C.-J. Wang, J. Mao, and J.-M. Bai (YNAO) report:


We observed the field of GRB 160410A (Gibson et al., GCN 19271) with the 2.4-meter optical telescope at Gao-Mei-Gu (GMG) 
station of Yunnan Observatories. Observations began from 12:40:10 UT, Apr. 10th, 2016, about 7.5 hours after the trigger. 
We marginallydetected one faint source in the image at the afterglow position (Yates et al. GCN 19272), and the magnitude was 
estimated as R~22.1+/- 0.2 mag.


GRB_name: GRB160411A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19281
SUBJECT: GRB 160411A: Swift-XRT observations
DATE:    16/04/11 03:10:17 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

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

The XRT began observing the field of GRB 160411A at 02:21:04.2 UT,
3132.3 seconds after the BAT trigger. Using promptly downlinked data we
find an uncatalogued X-ray source located at RA, Dec 349.35590,
-40.24247 which is equivalent to:
   RA(J2000)  = 23h 17m 25.42s
   Dec(J2000) = -40d 14' 32.9"
with an uncertainty of 4.0 arcseconds (radius, 90% containment). This
location is 103 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 1.61
x 10^20 cm^-2 (Willingale et al. 2013). 


GRB_name: GRB160410A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19282
SUBJECT: GRB 160410A: Swift-XRT refined Analysis
DATE:    16/04/11 05:36:03 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

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

We have analysed 5.7 ks of XRT data for GRB 160410A (Gibson et al. GCN
Circ. 19271), from 72 s to 67.9 ks after the  BAT trigger. The data
comprise 241 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. 19273).

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.54 (+/-0.11).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.28 (+0.12, -0.06). The
best-fitting absorption column is  consistent with the Galactic value
of 1.8 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has
a photon index of 1.9 (+0.8, -0.5) and a best-fitting absorption column
of 2 (+34, -2) 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 (3.8 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 (+34, -2) x 10^21 cm^-2 at z=1.717
Photon index:      1.9 (+0.8, -0.5)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00682269.

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


GRB_name: GRB160411A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19283
SUBJECT: GRB 160411A: Enhanced Swift-XRT position
DATE:    16/04/11 06:35:06 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 1177 s of XRT Photon Counting mode data and 3 UVOT
images for GRB 160411A, 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 = 349.35691, -40.24227 which is equivalent
to:

RA (J2000): 23h 17m 25.66s
Dec (J2000): -40d 14' 32.2"

with an uncertainty of 2.4 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: GRB160411A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19284
SUBJECT: GRB 160411A: MASTER-NET early optical observations.
DATE:    16/04/11 08:06:17 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
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.Senik
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)

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 SAAO was pointed to the  GRB160411A 34 sec after notice time 
and 64 sec after trigger time at 2016-04-11 01:30:00 UT. On our first (10s 
exposure)  set we haven't found optical transient  within SWIFT error-box 
(Page et al GCN 19279, Evans et al GCN 19283).
The 5-sigma upper limit has been about 16.0 mag  on single (10 sec 
exposure) and 18.5  on coadd (170 sec exposure) image.
The observations made on high zenit distance (z=80 deg).
The message may be cited.


GRB_name: GRB160410A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19285
SUBJECT: GRB 160410A: MITSuME Akeno optical upper limits
DATE:    16/04/11 09:43:58 GMT
FROM:    Taketoshi Yoshii at Tokyo Tech  <yoshii.t.ac@m.titech.ac.jp>

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

We searched for the optical counterpart of GRB 160410A (S. L. Gibson et al., GCN Circular #19271) 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 2016-04-10 12:06:25 UT (~7.1 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+[hour]    MID-UT     T-EXP[sec]      g'         Rc          Ic
----------------------------------------------------------------------------
   7.1        13:24:39         4694       >19.8     >19.7    >19.1
----------------------------------------------------------------------------
T0+ : Elapsed time after the burst 
T-EXP: Total Exposure time 
We used GSC2.3 catalog for flux calibration.


GRB_name: GRB160411A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19286
SUBJECT: GRB 160411A: Swift-XRT refined Analysis
DATE:    16/04/11 10:57:19 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

C. Pagani (U. Leicester), A.P. Beardmore (U. Leicester), P.A. Evans (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 K.L. Page report on behalf of the Swift-XRT team:

We have analysed 6.7 ks of XRT data for GRB 160411A (Page et al. GCN
Circ. 19279), from 3.1 ks to 22.5 ks after the BAT trigger. The data
are entirely in Photon Counting (PC) mode. The enhanced XRT position
for this burst was given by Evans et al. (GCN Circ. 19283).

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.5 (+3.3, -0.9).

If the light curve continues to decay with a power-law decay index of
1.5, the count rate at T+24 hours will be 2.0 x 10^-4 count s^-1

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00682339.

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


GRB_name: GRB160410A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19287
SUBJECT: GRB 160410A: TAROT La Silla observatory early optical observations
DATE:    16/04/11 13:13:27 GMT
FROM:    Alain Klotz at IRAP-CNRS-OMP  <Alain.Klotz@free.fr>

Klotz A., Turpin D., Atteia J.L. (CNRS-OMP-IRAP),
Boer, M., Laugier, R. (CNRS-ARTEMIS),
Gendre B. (UVI - Etelman Obs.) report:

We imaged the field of GRB 160410A detected by SWIFT
(trigger 682269) with the TAROT robotic telescope (D=25cm)
located at the European Southern Observatory,
La Silla observatory, Chile.

The observations started 28s after the GRB trigger
(16.8s after the notice). Due to a technical problem
only the first exposure of 60s was taken.

The image is trailed (see the description in Klotz
et al., 2006, A&A 451, L39). We detect the UVOT
optical transcient discovered by Gibson et al. (GCNC 19271).

At the beginning of the trail (t0+28s) the magnitude is
R=18.4 (+/-0.3) and decays to R=18.7 (limiting magnitude)
at t0+46s. Then the OT became too faint to be detected
between t0+46 and t0+88s (Rlim=18.7).

Magnitudes were estimated with the nearby NOMAD1 stars
and are not corrected for galactic dust extinction.


GRB_name: GRB160410A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19288
SUBJECT: Konus-Wind observation of GRB 160410A (short/hard)
DATE:    16/04/11 14:38:02 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred@mail.ioffe.ru>

D. Frederiks, S. Golenetskii, R.Aptekar, 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 GRB 160410A (Swift/BAT observation:
Gibson et al., GCN 19271; Sakamoto et al., GCN 19276)
triggered Konus-Wind at T0=18592.644 s UT (05:09:52.644).

The light curve shows a short, hard pulse with a total duration is ~2 s.
The emission is seen up to ~4 MeV.

As observed by Konus-Wind, the burst had a fluence of
(1.20 Â± 0.3)x10^-5 erg/cm2 and a 16-ms peak energy flux,
measured from T0-0.016, of (2.8 Â± 0.4)x10^-5 erg/cm2
(both in the 20 keV - 10 MeV energy range).

The spectrum of the burst (measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 10 MeV range by a cutoff power-law
(CPL) function with the following model parameters:
the photon index alpha = -0.71(-0.20,+0.26),
and the peak energy Ep = 1416(-356,+528) keV,
chi2 = 92/97 dof.
Fitting this spectrum with the GRB (Band) function yields
the same alpha and Ep with only an upper limit on beta of -2.1,
chi2 = 92/96 dof.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB160410_T18592/

Assuming the redshift z=1.717 (Selsing et al., GCN 19274)
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 ~4.0x10^52 erg,
the peak luminosity L_iso is ~7.5x10^52 erg/s,
and the rest-frame peak energy of the time-integrated spectrum,
Ep,i, is ~4660 keV.

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


GRB_name: GRB160411A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19289
SUBJECT: GRB 160411A: Fermi GBM detection
DATE:    16/04/11 16:29:44 GMT
FROM:    Oliver Roberts at UCD/Fermi  <oliver.roberts@ucd.ie>

O.J. Roberts (UCD), C.M. Hui (NASA/MSFC) report on
behalf of the Fermi GBM Team:

"At 01:28:52.52 UT on the 11th of April 2016, the Fermi
Gamma-Ray Burst Monitor triggered and located GRB 160411A
(trigger 482030936 / 160411062), which was also detected by
Swift (Page et al. 2016, GCN 19279). 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 XRT position is about 108 degrees.

The GBM light curve consists of a weak, short burst with a
duration (T90) of about 0.2 s (50-300 keV). The time-averaged
spectrum from T0-0.51 s to T0-0.35 s is best fit by a power
law function with an exponential high-energy cutoff function,
with Epeak = 161 +/- 37 keV and alpha = 0.26 +/- 0.67.

The event fluence (10-1000 keV) in this time interval is
(1.38 +/- 0.30)E-07 erg/cm^2. The 64ms peak photon flux
measured starting from T0-0.51 s in the 10-1000 keV band
is 6.4 +/- 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: GRB160410A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19290
SUBJECT: GRB 160410A: UKIRT near-IR upper limits
DATE:    16/04/11 17:24:13 GMT
FROM:    Wen-fai Fong at U of Arizona  <wfong@email.arizona.edu>

W. Fong and P. Milne (University of Arizona) report:

"We observed the field of the short-duration GRB 160410A (Gibson et al.,
GCN 19271) with the Wide Field Camera (WFCAM) mounted on the 3.8-m United
Kingdom Infrared Telescope (UKIRT) on Mauna Kea beginning on 2016 Apr
11.215 UT (25.3 hr post-burst). We obtained observations in the J- and
K-bands in 0.7" seeing. Using the quick-look pipeline ORAC-DR, we do not
detect any near-IR source in or around the positions of the X-ray
(Beardmore et al., GCN 19273) or optical (Yates et al., GCN 19272; Selsing
et al., GCN 19274; Marshall et al., GCN 19275; Trotter et al., GCN 19277)
afterglows. Calibrated to 2MASS, we therefore place 3-sigma limits of
J(AB)>20.0 mag and K(AB)>19.5 mag on the near-IR afterglow of GRB 160410A
at 25.3 hr post-burst. We note that this analysis is preliminary and a
final reduction of the images are expected to be ~1.5 mag deeper.

We thank Sam Benigni for executing these observations. In addition, we
thank Watson Varricatt, Tom Kerr, and Richard Green for their assistance in
re-establishing a system for a target-of-opportunity program at UKIRT."


GRB_name: GRB160411A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19291
SUBJECT: GRB 160411A: Swift/UVOT Upper Limits
DATE:    16/04/11 17:40:56 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <siegel@swift.psu.edu>

M. H. Siegel (PSU) and K. L. Page (U Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 160411A
3139 s after the BAT trigger (Page et al., GCN Circ. 19279).
No optical afterglow consistent with the XRT position
(Perri et al. GCN Circ. 19281)
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          3139         3289          147         >20.5
white             3139         4521          344         >21.0
v                 3295         4931          393         >19.4
b                 4116         4316          197         >19.9
u                 3910         5546          393         >20.0
w1                3705         5342          393         >20.2
m2                3500         5136          393         >20.1
w2                4527         4726          197         >20.0

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: GRB160411A
Detection_method: GROND
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19292
SUBJECT: GRB 160411A: GROND Optical/NIR upper limits
DATE:    16/04/11 18:19:10 GMT
FROM:    Robert Yates at MPE/Swift  <robyates@mpe.mpg.de>

R Yates, T-W Chen, and J Greiner (all MPE Garching) report on behalf of
the GROND team:

We observed the field of GRB 160411A (Swift trigger 682339; Page et al.,
GCN #19279) 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 09:14 UT on 11-04-2016, 7 hr 45 min after the GRB
trigger. They were performed at an average seeing of 1.9" in the r'-band
and at an average airmass of 1.8.

Based on the first 49 min of total exposures, we do not detect a source
within the 4.0" Swift-XRT error circle reported by Perri et al. (GCN
#19281) down to (all in the AB system):

g' > 23.7 mag,
r' > 23.9 mag,
i' > 23.1 mag,
z' > 22.9 mag,
J > 21.3 mag,
H > 20.8 mag, and
K > 19.9 mag.

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)=0.02 mag in
the direction of the burst (Schlafly & Finkbeiner 2011).


GRB_name: GRB160411A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19293
SUBJECT: GRB 160411A: Gemini-S optical observations
DATE:    16/04/11 18:34:24 GMT
FROM:    Andrew Levan at U.of Leicester  <A.J.Levan@warwick.ac.uk>

A.J.Levan (U. Warwick), W. Fong (Arizona) report on behalf of a larger collaboration:

â€œWe observed the location of GRB 160411A (Page et al. GCN 19279, Evans et al. GCN 19283) with Gemini-S and GMOS starting at 09:35 UT on 2016 April 11. Observations were taken in the i-band and began 9 hours after the BAT trigger. They were taken at the start of morning twilight as the source was rising, because of this the seeing is poor (1.4â€) and depth relatively shallow. 

The region around the enhanced XRT position is relatively complex, with multiple sources in the surrounding area. Two obvious sources are located just outside the Eastern and Western edge of the XRT circle at locations of

Source A: 
RA(J2000) 23:17:25.99
DEC(J2000) -40:14:32.0

Source B: 
RA(J2000) 23:17:25.37
DEC(J2000) -40:14:30.5

The sources have comparable magnitude and appear to be marginally extended, although the poor seeing and signal to noise complicates such analyses. 

With thank the Gemini staff, in particular Bryan Miller, for their assistance with these observationsâ€ 


GRB_name: GRB160408A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19294
SUBJECT: GRB 160408A: 6.0 GHz VLA upper limit
DATE:    16/04/11 19:13:39 GMT
FROM:    Wen-fai Fong at U of Arizona  <wfong@email.arizona.edu>

W. Fong (University of Arizona) reports:

"We observed the field of the short-duration GRB 160408A (Evans et al., GCN
19260) with the Karl G. Jansky Very Large Array (VLA) beginning on 2016 Apr
8.889 UT (14.91 hr post-burst) at a mean frequency of 6.0 GHz. In 1 hour of
observations, we do not detect any radio source within or around the
enhanced XRT position (Osborne et al., GCN 19261) or the optical afterglow
position (Levan et al., GCNs 19262, 19269) to a 3-sigma limit of 21.5
microJy. We therefore place a 3-sigma limit of 21.5 microJy on the radio
afterglow of GRB 160408A at 14.91 hr after the burst.

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


GRB_name: GRB160410A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19295
SUBJECT: GRB 160410A: NOT observations of the afterglow
DATE:    16/04/11 21:27:08 GMT
FROM:    Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst  <malesani@dark-cosmology.dk>

D. Malesani (DARK/NBI) and C. Kirkpatrick (Univ. Helsinki) report on 
behalf of a larger collaboration:

We observed the optical counterpart of GRB 160410A (Gibson et al., GCN 
19271) with the Nordic Optical Telescope (NOT) equipped with ALFOSC. 
Observations started on April 10.92 UT and consisted of 3x900 s 
exposures in the SDSS r band.

The optical counterpart of GRB 160410A is well detected with a magnitude 
r = 24.15 +- 0.09 (AB), calibrated against nearby SDSS stars, at a mean 
epoch April 10.936 UT (17.3 hr after the GRB). The source looks 
pointlike in our images (with a seeing of 0.65").


GRB_name: GRB160409A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19296
SUBJECT: GRB 160409A: Swift ToO observations
DATE:    16/04/12 00:45:16 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 Swift/BAT GRB 160409A. 
Automated analysis of the XRT data will be presented online at
http://www.swift.ac.uk/ToO_GRBs/00020604

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 Swift/BAT 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: GRB160408A
Detection_method: CALET
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19297
SUBJECT: GRB 160408A: CALET Gamma-Ray Burst Monitor detection
DATE:    16/04/12 02:48:31 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto@phys.aoyama.ac.jp>

W. Ishizaki (ICRR), A. Yoshida, T. Sakamoto, Y. Kawakubo, M. Moriyama, 
Y. Yamada (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), I. Takahashi (IPMU), 
Y. Asaoka, S. Ozawa, S. Torii (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), 
M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena) 
and the CALET collaboration:

The short-duration GRB 160408A (Swift, Evans et al. GCN Circ. 19260; 
Fermi-GBM, Roberts et al. GCN Circ. 19265;  INTEGRAL-ACS, Trigger #7441) 
triggered the CALET Gamma-Ray Burst Monitor (CGBM) at 6:25:37.4 on 
8 April 2016.  The burst signal was detected by all CGBM instruments.

The light curve of the SGM shows a single peak.  The emission starts at T0+6.4 sec, 
peaks at T0+6.5 sec and ends at T0+7.1 sec.  The T90 duration 
measured by the SGM data is 0.38 +- 0.18 sec (40-1000 keV). 

The CGBM data used in this analysis are provided by the Waseda CALET Operation Center 
located at the Waseda University.


GRB_name: GRB160412A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19298
SUBJECT: GRB 160412A: Swift detection of a burst
DATE:    16/04/12 04:37:25 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

S. L. Gibson (U Leicester), A. Y. Lien (GSFC/UMBC),
K. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU)
report on behalf of the Swift Team:

At 04:23:54 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160412A (trigger=682522).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 33.107, -67.645 which is 
   RA(J2000) = 02h 12m 26s
   Dec(J2000) = -67d 38' 42"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex
peak structure with a duration of about 80 sec.  The peak count rate
was ~1800 counts/sec (15-350 keV), at ~13 sec after the trigger. 

The XRT began observing the field at 04:25:13.5 UT, 78.8 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 33.0482, -67.6266 which is equivalent to:
   RA(J2000)  = +02h 12m 11.57s
   Dec(J2000) = -67d 37' 35.8"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). This
location is 104 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. 

The initial flux in the 2.5 s image was 9.17e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 90 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
0.04. 

Burst Advocate for this burst is S. L. Gibson (slg44 AT 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: GRB160412A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19299
SUBJECT: GRB 160412A: Enhanced Swift-XRT position
DATE:    16/04/12 10:50:42 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 2983 s of XRT Photon Counting mode data and 4 UVOT
images for GRB 160412A, 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 = 33.04586, -67.62664 which is equivalent
to:

RA (J2000): 02h 12m 11.01s
Dec (J2000): -67d 37' 35.9"

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: GRB160410A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19300
SUBJECT: GRB 160410A: further NOT optical observations
DATE:    16/04/12 12:35:22 GMT
FROM:    Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst  <malesani@dark-cosmology.dk>

D. Malesani (DARK/NBI), D. Xu (NAOC/CAS), T. Kuutma (NOT and Tartu 
Obs.), report on behalf of a larger collaboration:

We observed again the optical counterpart of GRB 160410A (Gibson et al., 
GCN 19271) with the Nordic Optical Telescope (NOT) equipped with ALFOSC. 
Observations started on April 11.87 UT and consisted of 4x900 s 
exposures in the SDSS r band.

At a mid time of 40.37 hr after the GRB, we do not detect any longer the 
optical afterglow down to a 3-sigma limiting magnitude of r > 25 (AB), 
calibrated against nearby SDSS stars. The corresponding decay index (F 
propto t^-alpha) between our two NOT observations (Malesani & 
Kirkpatrick, GCN 19925) is constrained to be alpha > 0.9. The object 
closest to the GRB position (with r ~ 24) lies 4.7" away, so we cannot 
single out any obvious host galaxy candidate to the GRB, down to the 
quoted limiting magnitude.


GRB_name: GRB160412A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19301
SUBJECT: GRB 160412A: Swift-BAT refined analysis
DATE:    16/04/12 12:42:18 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), S. L. Gibson (U Leicester), 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-61 to T+242 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 160412A (trigger #682522)
(Gibson, et al., GCN Circ. 19298).  The BAT ground-calculated position is
RA, Dec = 33.074, -67.636 deg, which is 
   RA(J2000)  =  02h 12m 17.7s 
   Dec(J2000) = -67d 38' 08.8" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 75%.
 
The mask-weighted light curves shows several overlapping peaks starting at
~T-10 sec, peaking at ~T+15 sec, and ending at ~T+70 sec.
T90 (15-350 keV) is 31.6 +- 4.0 sec (estimated error including systematics).
 
The time-averaged spectrum from T-3.35 to T+40.18 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.88 +- 0.08.  The fluence in the 15-150 keV band is 1.9 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+14.40 sec in the 15-150 keV band
is 1.6 +- 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/682522/BA/


GRB_name: GRB160411A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19302
SUBJECT: GRB 160411A: Swift-BAT refined analysis of the short burst
DATE:    16/04/12 12:52:25 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.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), K. L. Page (U Leicester), 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 downlinks,
we report further analysis of BAT short GRB 160411A (trigger #682339)
(Page, et al., GCN Circ. 19279).  The BAT ground-calculated position is
RA, Dec = 349.370, -40.258 deg, which is 
   RA(J2000)  =  23h 17m 28.8s 
   Dec(J2000) = -40d 15' 30.3" 
with an uncertainty of 2.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 27%.
 
The mask-weighted light curve shows two overlapping peaks starting at
~T+0.0 and ending at ~T+0.5 sec.  T90 (15-350 keV) is 0.36 +- 0.08 sec
(estimated error including systematics).
 
The time-averaged spectrum from T+0.06 to T+0.46 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.43 +- 0.28.  The fluence in the 15-150 keV band is 8.0 +- 1.8 x 10^-8 erg/cm2.
The 1-sec peak photon flux measured from T-0.24 sec in the 15-150 keV band
is 1.5 +- 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/682339/BA/
 


GRB_name: GRB160412A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19303
SUBJECT: GRB 160412A: Swift-XRT refined Analysis
DATE:    16/04/12 16:51:07 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P.A. Evans (U. Leicester), V. D'Elia (ASDC), 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 S.L. Gibson
report on behalf of the Swift-XRT team:

We have analysed 6.1 ks of XRT data for GRB 160412A (Gibson et al. GCN
Circ. 19298), from 68 s to 30.8 ks after the  BAT trigger. The data
comprise 267 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. 19299).

The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=3.14 (+0.20, -0.25). At T+107 s  the decay
steepens to an alpha of 5.67 (+0.18, -0.19) before breaking again at
T+377 s to a final decay with index alpha=0.26 (+/-0.08).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 3.05 (+0.11, -0.10). The
best-fitting absorption column is  4.4 (+/-0.3) x 10^21 cm^-2, in
excess of the Galactic value of 4.4 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 2.4 (+0.4, -0.3) and
a best-fitting absorption column of 2.6 (+1.3, -1.0) x 10^21 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 2.9 x 10^-11 (5.2 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      2.6 (+1.3, -1.0) x 10^21 cm^-2
Galactic foreground: 4.4 x 10^20 cm^-2
Excess significance: 3.4 sigma
Photon index:      2.4 (+0.4, -0.3)

If the light curve continues to decay with a power-law decay index of
0.26, the count rate at T+24 hours will be 0.023 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 6.6 x
10^-13 (1.2 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/00682522.

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


GRB_name: GRB160409A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19304
SUBJECT: GRB 160409A found in Swift BAT ground analysis
DATE:    16/04/12 19:20:11 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

GRB 160409A found in Swift BAT ground analysis

P.A. Evans (U. Leicester),  J.P. Osborne (U Leicester), 
K. L. Page (U Leicester), and  D.M. Palmer (LANL)
report on behalf of the Swift Team

At 05:54:14 UT on 2016-04-09 BAT triggered and located
GRB 160409A (trigger #682162).  Swift did not immediately 
slew to this source because its location approximately
matched a known source (4U 1916-053) in its on-board catalog.  
The BAT on-board calculated location is 
RA, dec 289.705,-5.390 which is 
RA(J2000) = 19h 18m 49s
Dec(J2000) = -5d 23' 24"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex
peak structure with a duration of about 30 sec.  The peak count rate
was ~1300 counts/sec (15-350 keV), at ~2 sec after the trigger.

The catalogued source, 4U 1916-053, is identified by Simbad as being
the LXB V* V1405 Aql.  However, this object is 9 arcminutes from the 
BAT position, and well outside the error circle.  BAT has detected a burst
from that source (1.1 arcmin offset from the V1405 Aql location)
in April 2006.  During the 6-minute accumulation that overlaps the
trigger, SAX J2103.5+4545 is detected (at lower significance and 
correspondingly larger position uncertainty) with a 3.3 arcmin offset.
Therefore we can confidently state that this trigger did not come
from the location of V1405 Aql and is due to a different source.

A Swift Target of Opportunity was requested and XRT began
observing the field at 00:34:58 UT on 2016-04-12, which is
2.8 days after the BAT trigger. No unknown sources were 
detected in the 3 kiloseconds of data, although two known 
sources and possible scattered X-rays from V1405 Aql were seen.
No new sources were detected in UVOT down to a limiting
magnitude of 21.3 in white.

Qualitatively, about half of long GRBs would be visible in a 
3 ks XRT observation at that delay after the trigger, so the 
non-detection of an afterglow does not rule out a GRB.


GRB_name: GRB160409A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19305
SUBJECT: GRB 160409A: Swift-XRT observations
DATE:    16/04/12 19:24:04 GMT
FROM:    Sarah Gibson at U.of Leicester  <slg44@leicester.ac.uk>

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), S.L. Gibson (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
Swift/BAT-detected burst GRB 160409A, collecting 3.0 ks of Photon
Counting (PC) mode data between T0+240.0 ks and T0+246.7 ks. 

No uncatalogued X-ray sources have been detected inside or close to the
Swift/BAT error region. The 3-sigma upper limit in the field ranges
from ~0.004 to ~0.005 ct s^-1, corresponding to a 0.3-10 keV observed
flux of 1.7e-13 to 2.1e-13 erg cm^-2 s^-1 (assuming a typical GRB
spectrum).

A previously-catalogued X-ray source has been detected inside or close
to the Swift/BAT error region, however because it is a catalogued
object it is unlikely to be the afterglow.

An uncatalogued was detected, however this was too far from the GRB
position to be the afterglow.

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/00020604.

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


GRB_name: GRB160410A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19306
SUBJECT: GRB 160410A: JCMT SCUBA-2 sub-mm observation
DATE:    16/04/12 19:25:53 GMT
FROM:    Ian Smith at Rice U  <ian@spacsun.rice.edu>

I.A. Smith (Rice U.), N.R. Tanvir (U. of Leicester), and Y. Urata (NCU) 
report:

We observed the location of the short GRB 160410A (Gibson et al., 
GCN Circ. 19271) using the SCUBA-2 sub-millimeter continuum camera 
on the James Clerk Maxwell Telescope.  The observation started at 
05:54 UT on 2016-04-10, corresponding to 45 minutes after the burst 
trigger.  Exposures totaling 2.0 hours were made in good weather 
conditions.  No source was detected, with the RMS background noise 
being 1.3 mJy/beam at 850 microns and 12.5 mJy/beam at 450 microns.

We thank Callie Matulonis, Lianghao Lin, and Iain Coulson for the prompt 
support of these observations that were taken under project M16AP005.


GRB_name: GRB160412A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19308
SUBJECT: GRB 160412A: Swift/UVOT Upper Limits
DATE:    16/04/12 21:09:39 GMT
FROM:    Frank Marshall at GSFC  <femarsha@khamseen.gsfc.nasa.gov>

F. E. Marshall (NASA/GSFC) and S. L. Gibson (U. Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 160412A
90 s after the BAT trigger (Gibson et al., GCN Circ. 19298).
No optical afterglow consistent with the enhanced XRT position
(Goad et al. GCN Circ. 19299)
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            90          240          147         >20.4
u_FC               303          552          246         >19.1
white               90         1878          431         >21.1
v                  633         2101          175         >19.3
b                  558         2026          156         >19.7
u                  303         2001          362         >19.5
w1                 682         2150          156         >19.8
m2                1063         2125           97         >19.2
w2                 608         2076          175         >19.7

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: GRB160410A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19309
SUBJECT: GRB 160410A: TLS Tautenburg observations
DATE:    16/04/12 21:16:50 GMT
FROM:    Sebastian Schmidl at TLS Tautenburg  <schmidl@tls-tautenburg.de>

I. Juvan (IWF Graz), M. Bluemcke, D. Baak (University of Jena), S. Kunz,
S. Schmidl, S. Klose, D. A. Kann, A. Nicuesa Guelbenzu, and F. Ludwig
(TLS Tautenburg) report:

We observed the field of GRB 160410A (Gibson et al., GCN 19271) with
the Tautenburg 1.34-m Schmidt telescope at a mid-time of about 14.6 hrs
after the GRB trigger, at a mean airmass of 1.5. We obtained 4 x 300s
and 1 x 600s exposures in the Ic band.

We do not detect the optical afterglow reported by Gibson et al. (GCN
19271), Yates et al. (GCN 19272), Selsing et al. (GCN 19274), Trotter et
al. (GCN 19277), Wang et al. (GCN 19280) and Klotz et al (GCN 19287).
We estimate a preliminary upper limit of Ic > 21.1 mag (AB magnitude
system), calibrated against SDSS field stars.

These observations were performed as part of the Tautenburg Observing
School at the Thueringer Landessternwarte.


GRB_name: GRB160410A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19311
SUBJECT: GRB 160410A: SMARTS optical/IR observations
DATE:    16/04/13 02:55:57 GMT
FROM:    Bethany Cobb at GWU  <bcobb@gwu.edu>

B. E. Cobb (GWU) reports:

Using the ANDICAM instrument on the 1.3m telescope at CTIO, we
obtained optical/IR imaging of the error region of GRB 160410A
(GCN 19271, Gibson et al.) with a mid-exposure time of 20.7 hours
post-burst (2016-04-11 01:49 UT). Total summed exposure times
amounted to 36 minutes in I and 30 minutes in J.

No source is detected at the position of the optical
afterglow (e.g. GCN 19271, Gibson et al.; GCN 19272, Yates
et al.) to approximate limiting magnitudes of I > 20.3 and J > 17.5.
Magnitudes are calibrated using USNO-B1.0 stars in I,
and 2MASS stars in J.


GRB_name: GRB160409A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19312
SUBJECT: Konus-Wind observation of GRB 160409A
DATE:    16/04/13 13:13:04 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred@mail.ioffe.ru>

D. Frederiks, S. Golenetskii, R.Aptekar, 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 160409A (Swift-BAT ground detection:
Evans et al., GCN 19304) triggered Konus-Wind
at T0=21254.430 s UT (05:54:14.430).

The KW light curve shows single structure-less pulse with
a total duration of ~35 s.
The emission is visible up to ~7 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB160409_T21254/

As observed by Konus-Wind, the burst had a fluence
of 1.8(-0.3,+0.3)x10^-5 erg/cm2, and a 64-ms peak flux,
measured from T0+4.846 s, of 1.5(-0.2,+0.2)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum (measured from T0 to T0+24.832 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 = -0.68(-0.16,+0.18),
and the peak energy Ep = 209(-18,+22) keV,
chi2 = 107/98 dof.
Fitting this spectrum with the GRB (Band) function yields
the same alpha and Ep with an upper limit on beta of -2.1

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 the cutoff power law with the following model parameters:
the photon index alpha = -0.72(-0.17,+0.19),
and the peak energy Ep = 252(-26,+32) keV,
chi2 = 122/98 dof.
Fitting this spectrum with the GRB (Band) function yields
the same alpha and Ep with an upper limit on beta of -2.0

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


GRB_name: GRB160411A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19313
SUBJECT: GRB 160411A - Gemini-S afterglow candidate
DATE:    16/04/13 18:49:20 GMT
FROM:    Andrew Levan at U.of Leicester  <A.J.Levan@warwick.ac.uk>

A.J. Levan (U. Warwick), W. Fong (Arizona) and N.R. Tanvir (Leicester) report on behalf of a larger collaboration:

â€œWe obtained a second epoch of i-band observations of the short-GRB 160411A (Page et al. GCN 19279) on 2016 April 13, 10:01 UT. Photometry suggests that our previously identified source B (Levan & Fong GCN 19293) has faded by approximately 0.9 magnitudes between the two epochs obtained 48 hours apart, although a source close to this location is still faintly detected in our imaging. We therefore suggest this source may be the optical afterglow of GRB 160411A.

We thank the Gemini staff, in particular Bryan Miller and Rodolfo Angeloni for assistance with these observations.â€


GRB_name: GRB160412A
Detection_method: correction
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19314
SUBJECT: GRB 160412A: GROND upper limits
DATE:    16/04/14 09:54:48 GMT
FROM:    Jan Bolmer at MPE/Garching  <jan@bolmer.de>

J. Bolmer, T. Schweyer and J. Greiner (all MPE Garching) report on behalf
of the GROND Team:

We observed the field of GRB 160412A (Swift trigger 682522; Gibson et
al., GCN #19298) simultaneously in g'r'i'z'JHK with GROND (Greiner et al.
2008, PASP 120, 405) mounted at the 2.2m MPG telescope at the ESO La Silla
Observatory (Chile).

Observations started at 23:11 UT on 2016-04-12, 18.8 h after the GRB
trigger. They were performed at an average seeing of 2.5â€œ and at an
average airmass of 2.3.

We detect no source within or close to the Swift-XRT error circle
reported by Goad et al. (GCN #19299).

Based on 36 min of exposure in g'r'i'z' and 37 min in JHK, at a mid-time
of 023:35 UT, we derive the following preliminary upper
limits (in AB system):

g' > 23.5 mag,
r' > 23.6 mag,
i' > 22.9 mag,
z' > 22.7 mag,
J > 20.2 mag,
H > 29.6 mag, and
K_s > 19.7 mag.

Given upper limits are calibrated against GROND zeropoints (g'r'i'z')
as well as 2MASS field stars (JHK_s). No correction for the expected Galactic
foreground extinction corresponding to a reddening of E_(B-V)=0.03 mag in
the direction of the burst (Schlafly & Finkbeiner 2011) has been applied.


GRB_name: GRB160417A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19316
SUBJECT: GRB 160417A: Swift detection of a burst with an optical counterpart
DATE:    16/04/17 04:34:46 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

P. D'Avanzo (INAF-OAB), A. Melandri (INAF-OAB), D. M. Palmer (LANL),
B. Sbarufatti (INAF-OAB/PSU) and M. H. Siegel (PSU) report on behalf
of the Swift Team:

At 04:23:41 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160417A (trigger=683076).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 120.240, +7.671 which is 
   RA(J2000) = 08h 00m 58s
   Dec(J2000) = +07d 40' 15"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex peak
structure with a duration of about 30 sec.  The peak count rate
was ~1100 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 04:25:53.1 UT, 132.2 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source located at RA, Dec 120.25774, 7.66265 which
is equivalent to:
   RA(J2000)  = 08h 01m 01.86s
   Dec(J2000) = +07d 39' 45.5"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 70 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 2.92
x 10^20 cm^-2 (Willingale et al. 2013). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 135 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  = 08:01:01.64 = 120.25682
  DEC(J2000) = +07:39:46.4  = 7.66290
with a 90%-confidence error radius of about 0.64 arc sec. This position is 4.4
arc sec. from the center of the XRT error circle. The estimated magnitude is
19.15 with a 1-sigma error of about  0.15. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.02. 

Burst Advocate for this burst is P. D'Avanzo (paolo.davanzo 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: GRB160417A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19317
SUBJECT: GRB 160417A: KAIT optical afterglow confirmation
DATE:    16/04/17 05:00:15 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 160417A (D'Avanzo et al.,
GCN 19316) about 10 minutes after the trigger. 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 =  08:01:01.64 (J2000)
DEC= +07:39:46.60 (J2000)

The object location is consistent with the position reported
from UVOT (D'Avanzo et al., GCN 19316). The object has clear band mag
of ~17.9 about 10 minutes after the burst.

Follow-up observations are encouraged.


GRB_name: GRB160417A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19318
SUBJECT: GRB 160417A: Enhanced Swift-XRT position
DATE:    16/04/17 08:43:33 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 1095 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 160417A, 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 = 120.25686, +7.66288 which is equivalent
to:

RA (J2000): 08h 01m 1.65s
Dec (J2000): +07d 39' 46.4"

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: GRB160417A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19319
SUBJECT: GRB 160417A: MITSuME Okayama upper limits
DATE:    16/04/17 14:44:24 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 160417A (D'Avanzo et al., GCNC 19316)
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 2016-04-17 11:06:00 UT (~6.7 h after
the burst). We could not detect the previously reported afterglow
(D'Avanzo et al., GCNC 19316; Zheng et al., GCNC 19317)
in all the three bands.

Three sigma upper limits of the OT are listed below.
We used SDSS-DR8 catalog for flux calibration.

#T0+[day]  MID-UT    T-EXP[sec]   g'    Rc     Ic
-----------------------------------------------------
0.32136    12:06:26    5640.0   >19.7  >19.7  >18.9
-----------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]


GRB_name: GRB160417A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19320
SUBJECT: GRB 160417A: Swift-XRT refined Analysis
DATE:    16/04/17 15:47:59 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

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), S.L. Gibson (U. Leicester), J.P. Osborne (U. Leicester),
K.L. Page (U. Leicester) and P. D'Avanzo report on behalf of the
Swift-XRT team:

We have analysed 8.0 ks of XRT data for GRB 160417A (D'Avanzo et al.
GCN Circ. 19316), from 117 s to 23.2 ks after the  BAT trigger. The
data comprise 41 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
Osborne et al. (GCN Circ. 19318).

The light curve can be modelled with an initial power-law decay with an
index of alpha=4.4 (+0.4, -0.3), followed by a break at T+305 s to an
alpha of 0.59 (+/-0.06).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.05 (+0.15, -0.08). The
best-fitting absorption column is  consistent with the Galactic value
of 2.9 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 3.1 x 10^-11 (3.4 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      2.9 (+/-1.9) x 10^20 cm^-2
Galactic foreground: 2.9 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:      2.05 (+0.15, -0.08)

If the light curve continues to decay with a power-law decay index of
0.59, the count rate at T+24 hours will be 0.013 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.9 x
10^-13 (4.3 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/00683076.

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


GRB_name: GRB160417A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19321
SUBJECT: GRB 160417A: iTelescope T11 optical observations
DATE:    16/04/17 17:10:58 GMT
FROM:    Veli-Pekka Hentunen at Taurus Hill Obs,A95  <veli-pekka.hentunen@kassiopeia.net>

Veli-Pekka Hentunen, Markku Nissinen and Tuomo Salmi (Taurus Hill
Observatory, Varkaus, Finland) report:

We have detected GRB 160417A optical afterglow at iTelescope observatory
T11 (Mayhill, New Mexico) using 0.50-m f/6.8 astrograph and FLI
PL11002M CCD. The observations were started at 2016-04-17
05:08:31 (UT). Two unfiltered images with 300 sec exposure time were taken.

The afterglow was detected at the position RA 08:01:01.65 and DEC
+07:39:47.6.

The following magnitude was obtained from the observations using
USNO-B1.0 0976-0191477 (R2=16.67) as a comparison star:

Tmid(s)+T0       Filter         Exp. time         Mag              Mag. Err.
2996                 Clear         2x300s           18.6CR          0.3

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GRB_name: GRB160417A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19322
SUBJECT: GRB 160417A: Swift/UVOT Detection
DATE:    16/04/17 18:40:24 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld@ucl.ac.uk>

A. A. Breeveld (UCL-MSSL) and P. D'Avanzo (INAF-OAB)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 160417A
136 s after the BAT trigger (D'Avanzo et al., GCN Circ. 19316).
The source reported for the UVOT in the initial GCN and also by Zheng 
and Filippenko (GCN Circ. 19317) is found to be fading.

The preliminary UVOT position is:
     RA  (J2000) =  08:01:01.64 = 120.25685 (deg.)
     Dec (J2000) = +07:39:46.4  =   7.66289 (deg.)
with an estimated uncertainty of 0.46 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              136          285          147         18.92 Â± 0.07
white              870         1020          147         19.14 0.10
v                  623         1070           58         18.54 Â± 0.31
b                  549         1169           58         19.07 Â± 0.21
u                  294          543          246         18.08 Â± 0.08
w1                 672         1280           64        >18.9
m2                 647         1268           78        >19.1
w2                 599         1220           78        >18.8

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: GRB160417A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19323
SUBJECT: GRB 160417A: Swift-BAT refined analysis
DATE:    16/04/17 21:26:47 GMT
FROM:    Tilan Ukwatta at LANL  <tilan.ukwatta@gmail.com>

S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC),
P. D'Avanzo (INAF-OAB), 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-239 to T+963 sec from the recent
telemetry downlink, we report further analysis of BAT
GRB 160417A (trigger #683076) (D'Avanzo, et al.,
GCN Circ. 19316).  The BAT ground-calculated position is
RA, Dec = 120.260, 7.646 deg which is
   RA(J2000)  =  08h 01m 02.4s
   Dec(J2000) = +07d 38' 45.6"
with an uncertainty of 1.9 arcmin, (radius, sys+stat,
90% containment). The partial coding was 41%.

The mask-weighted light curve shows a multi-peak episode
starting ~T-4 sec, and ending around ~T+20 sec.
T90 (15-350 keV) is 15 +- 2 sec (estimated error including
systematics).

The time-averaged spectrum from T-2.14 to T+13.89 sec
is best fit by a simple power-law model.  The power law index
of the time-averaged spectrum is 1.93 +- 0.24.  The fluence
in the 15-150 keV band is 5.9 +- 0.8 x 10^-07 erg/cm2.
The 1-sec peak photon flux measured from T+1.51 sec in the
15-150 keV band is 1.0 +- 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/683076/BA/


GRB_name: GRB160417A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19324
SUBJECT: GRB 160417A: GMG observations
DATE:    16/04/18 03:17:12 GMT
FROM:    Jirong Mao at Yunnan Obs  <jirongmao_obs@ynao.ac.cn>

J.-J. Zhang, J. Mao, and J.-M. Bai (YNAO) report:


We observed the field of GRB 160417A (D'Avanzo et al., GCN 19316) with the 2.4-meter optical telescope at Gao-Mei-Gu (GMG)
station of Yunnan Observatories. Observations began from 12:30:03 UT, Apr. 17th, 2016, about 8.2 hours after the trigger. 
We obtained the following results at the afterglow position: r~21.1+/- 0.3 mag, i>20.9 mag, and g>21.8 mag.


GRB_name: GRB160419A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19326
SUBJECT: GRB 160419A: Swift detection of a burst
DATE:    16/04/19 15:32:18 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

C. B. Markwardt (NASA/GSFC), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA), A. Melandri (INAF-OAB),
K. L. Page (U Leicester), D. M. Palmer (LANL), M. H. Siegel (PSU) and
T. N. Ukwatta (LANL) report on behalf of the Swift Team:

At 15:16:37 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160419A (trigger=683383).  Swift did not slew to the
burst due to an observing constraint. 
The BAT on-board calculated location is 
RA, Dec 16.424, -27.343 which is 
   RA(J2000) = 01h 05m 42s
   Dec(J2000) = -27d 20' 32"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single symmetric 
peak structure with a duration of about 20 sec.  The peak count rate
was ~5000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

Due to a Sun observing constraint, Swift cannot slew to the BAT
position until 01:44 UT on 2016 April 30. There will thus be no XRT or
UVOT data for this trigger before this time. 

Burst Advocate for this burst is C. B. Markwardt (Craig.Markwardt 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: GRB160419A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19327
SUBJECT: GRB 160419A: Fermi GBM detection
DATE:    16/04/19 21:27:21 GMT
FROM:    Bagrat Mailyan at UAH  <bm0054@uah.edu>

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

"At 15:16:35.39  UT on 19 April 2016, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 160419A (trigger 482771799 / 160419.637), which
was also detected by the Swift/BAT (C. B. Markwardt et al. 2016, GCN 19326).
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 BAT position is about 127 degrees.

The GBM light curve consists of a weak burst with a
duration (T90) of about 24 s (50-300 keV). The time-averaged
spectrum from T0-1.3 s to T0+2.7 s is best fit by a power
law function with an exponential high-energy cutoff function,
with Epeak = 438 +/- 118 keV and alpha = -0.49 +/- 0.28.

The event fluence (10-1000 keV) in this time interval is
(1.675 +/- 0.221)E-06 erg/cm^2. The 1s peak photon flux
measured starting from T0-1.15 s in the 10-1000 keV band
is 1.92 +/- 0.25 ph/s/cm^2.

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

[GCN OPS NOTE(20apr16):  In the Subject line, "150419A" was changed to "160419A"]


GRB_name: GRB160419A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19328
SUBJECT: GRB 160419A, Swift-BAT refined analysis
DATE:    16/04/21 12:58:28 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), M. Stamatikos (OSU),
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

Using the data set from T-240 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 160419A (trigger #683383)
(Markwardt et al., GCN Circ. 19326).  The BAT ground-calculated position is
RA, Dec = 16.418, -27.341 deg which is
  RA(J2000)  =  01h 05m 40.3s
  Dec(J2000) = -27d 20' 28.7"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 16%.

The mask-weighted light curve shows a triangle-shaped, single-peaked structure
that starts at ~ T-4 s, peaks at ~T0, and ends at ~T0+8 s. T90 (15-350 keV)
is 8.8 +- 1.1 sec (estimated error including systematics).

The time-averaged spectrum from T-4.5 to T+8.5 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 0.76 +- 0.33,
and Epeak of 107.1 +- 35.2 keV (chi squared 40.46 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 3.5 +- 0.2 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+0.00 sec in the 15-150 keV band is
8.9 +- 0.7 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.40 +- 0.07 (chi squared 53.01 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/683383/BA/


GRB_name: GRB160422A
Detection_method: Fermi LAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19329
SUBJECT: GRB 160422A: Fermi-LAT Detection
DATE:    16/04/22 19:26:41 GMT
FROM:    Judith Racusin at GSFC  <judith.racusin@nasa.gov>

M. Yassine (LUPM, Montpellier), J. L. Racusin (NASA/GSFC), and N. Omodei (Stanford) report on 
behalf of the Fermi-LAT team:

Fermi LAT detected high-energy emission associated with GRB 160422A, which was also detected 
by Fermi GBM (trigger 483019143 / 160422499) at 11:59:00.81 on April 22, 2016.

The best LAT on-ground location is found to be:

RA, Dec (J2000) = 42.05, -57.9 

with an error radius of 0.07 deg (90% containment, statistical error only).

This was 80 deg from the LAT boresight at the time of the trigger, and triggered an autonomous 
repoint of the spacecraft.  The GRB became unocculted by the Earth and entered the LAT field 
of view at ~T0+400 seconds.

The data from the Fermi-LAT show a significant increase in the event rate that is spatially correlated 
with the trigger with high significance.

The highest-energy photon is a 12 GeV event which is observed 770 seconds after the GBM trigger.

A Swift ToO has been requested for this burst.

The Fermi-LAT point of contact for this burst is Manal Yassine (manal.yassine@lupm.in2p3.fr).

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: GRB160422A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19330
SUBJECT: GRB 160422A: Swift ToO observations
DATE:    16/04/22 20:11:16 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 160422A. 
Automated analysis of the XRT data will be presented online at
http://www.swift.ac.uk/ToO_GRBs/00020605

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: GRB160422A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19331
SUBJECT: GRB 160422A: Fermi GBM observation
DATE:    16/04/22 21:44:08 GMT
FROM:    Eric Burns at U of Alabama  <eb0016@uah.edu>

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

"At 11:59:00.81 UT on 22 April 2016, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 160422A (trigger 483019144 / 160422499).

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 LAT location is 53 degrees. The GBM on-ground location is
consistent with the LAT location (Yassine et al., GCN 19329).

The GBM light curve consists of a single main peak
with a duration (T90) of about 12 s (50-300 keV).
The time-averaged spectrum from T0 s to T0+13.1 s is
well fit by a Band function with Epeak = 242 +/- 4 keV,
alpha = -0.95 +/- 0.01, and beta = -2.42 +/- 0.04.

The event fluence (10-1000 keV) in this time interval is
(8.68 +/- 0.04)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+8.0 s in the 10-1000 keV band
is 93.8 +/- 0.6 ph/s/cm^2.

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


GRB_name: GRB160419A
Detection_method: CALET
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19332
SUBJECT: GRB 160419A: CALET Gamma-Ray Burst Monitor detection
DATE:    16/04/22 22:58:00 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto@phys.aoyama.ac.jp>

M. L. Cherry (LSU), A. Yoshida, T. Sakamoto, Y. Kawakubo, M. Moriyama, 
Y. Yamada (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), I. Takahashi (IPMU), 
Y. Asaoka, S. Ozawa, S. Torii (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), 
W. Ishizaki (ICRR), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena) 
and the CALET collaboration:

The long-duration GRB 160419A (Markwardt et al., GCN circ. 19326; Mailyan et al., 
GCN circ. 19327) triggered the CALET Gamma-Ray Burst Monitor (CGBM) at 15:16:35.4 on 
19 April 2016.  The burst signal was seen by all CGBM instruments.  

The light curve of the HXM shows several spikes.  The emission starts from T0-2 sec, 
peaks at T0+3 sec and ends at T0+10 sec.  The T90 duration measured by the HXM2 data 
is 6.2 +- 0.9 sec (50-250 keV). 

The CGBM data used in this analysis are provided by the Waseda CALET Operation Center 
located at the Waseda University.


GRB_name: GRB160422A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19333
SUBJECT: GRB 160422A: Swift/UVOT Candidate Afterglow
DATE:    16/04/23 00:48:34 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 160422A
32624 s after the LAT trigger (Yassine et al. GCN Circ. 19329).
A candidate optical afterglow
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  02:48:22.79 =  42.09497 (deg.)
    Dec (J2000) = -57:52:30.4  = -57.87511 (deg.)
with an estimated uncertainty of 0.45 arc sec. (radius, 90% confidence).

Preliminary detections 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            33427        34064          627         19.71 +/- 0.07
u                32624        33420          783         19.05 +/- 0.11

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).

[GCN OPS NOTE(25apr16), Per author's request, the LAT reference was corrected.]


GRB_name: GRB160422A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19334
SUBJECT: GRB 160422A: Swift-XRT afterglow detection
DATE:    16/04/23 05:15:14 GMT
FROM:    Alessandro Maselli at INAF/IASF Palermo  <maselli@ifc.inaf.it>

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 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 160422A (Yassine et al. GCN Circ. 19329),
collecting 4.9 ks of Photon Counting (PC) mode data between T0+32.6 ks
and T0+45.8 ks. 

Three uncatalogued X-ray sources are detected inside or close to the
Fermi/LAT error region, of which one ("Source 1") is above the RASS
limit, and is therefore likely the GRB afterglow.  The position of this
source is RA, Dec=42.0947, -57.8757 which is equivalent to:

RA (J2000): 02:48:22.74
Dec(J2000): -57:52:32.6

with an uncertainty of 3.6 arcsec (radius, 90% confidence). This
position is 2.0 arcmin from the Fermi/LAT position and 2.6 arcsec from
the Swift-UVOT candidate optical afterglow (Marshall, GCN Circ. 19333).


The light curve can be modelled with a power-law decay with a decay
index of alpha=1.3 (+/-1.0).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.3 (+0.4, -0.3). The
best-fitting absorption column is  2.4 (+1.3, -1.0) x 10^21 cm^-2, in
excess of the Galactic value of 2.3 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 3.1 x 10^-11 (5.1 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      2.4 (+1.3, -1.0) x 10^21 cm^-2
Galactic foreground: 2.3 x 10^20 cm^-2
Excess significance: 3.5 sigma
Photon index:      2.3 (+0.4, -0.3)

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 0.017 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.2 x
10^-13 (8.5 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis of the likely afterglow
are at http://www.swift.ac.uk/ToO_GRBs/00020605/index_1.php.
The results of the full analysis of the XRT observations are available
at http://www.swift.ac.uk/ToO_GRBs/00020605.

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


GRB_name: GRB160424A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19335
SUBJECT: GRB 160424A: Swift detection of a burst
DATE:    16/04/24 11:58:50 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

A. Y. Lien (GSFC/UMBC), A. D'Ai (INAF-IASFPA), J. A. Kennea (PSU),
K. L. Page (U Leicester), D. M. Palmer (LANL), T. Sakamoto (AGU) and
M. H. Siegel (PSU) report on behalf of the Swift Team:

At 11:49:07 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160424A (trigger=683906).  Swift did not immediately slew
to the burst due to an observing constraint. 
The BAT on-board calculated location is 
RA, Dec 319.481, -60.405 which is 
   RA(J2000) = 21h 17m 55s
   Dec(J2000) = -60d 24' 18"
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 5 sec.  The peak count rate
was ~5000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

Due to an observing constraint, Swift will not slew until T0+48.7
minutes. There will be no XRT or UVOT data until this time. 

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: GRB160424A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19336
SUBJECT: GRB 160424A: Swift-XRT observations
DATE:    16/04/24 13:09:41 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), M. Perri (ASDC) and G. Tagliaferri (INAF-OAB)
report on behalf of the Swift-XRT team:

The XRT began observing the field of GRB 160424A at 12:40:02.1 UT,
3054.8 seconds after the BAT trigger. Using promptly downlinked data we
find a fading, uncatalogued X-ray source located at RA, Dec 319.48505,
-60.41481 which is equivalent to:
   RA(J2000)  = 21h 17m 56.41s
   Dec(J2000) = -60d 24' 53.3"
with an uncertainty of 3.8 arcseconds (radius, 90% containment). This
location is 36 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 (3.94 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 2.5
(+2.04/-1.82) x 10^21 cm^-2 (90% confidence). 


GRB_name: GRB160424A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19337
SUBJECT: GRB 160424A: Swift/UVOT Upper Limit
DATE:    16/04/24 14:06:06 GMT
FROM:    Frank Marshall at GSFC  <femarsha@khamseen.gsfc.nasa.gov>

F.E. Marshall (NASA/GSFC) and A. Lien (GSFC/UMBC)
report on behalf of the Swift/UVOT team:

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 3059 seconds after the BAT trigger (Lien et al. GCN Circ. 19335). 
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 region (Evans et al. GCN Circ 19336).  
Sensitivity is less than usual because of reduced pointing stability.
We estimate an upper limit of 16th mag.
No correction has been made
for the expected extinction corresponding to E(B-V) of 0.03.


GRB_name: GRB160424A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19338
SUBJECT: GRB 160424A: Swift-BAT refined analysis
DATE:    16/04/24 20:17:34 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. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
 
Using the data set from T-61 to T+243 sec from the recent telemetry downlinks,
we report further analysis of BAT GRB 160424A (trigger #683906)
(Lien, et al., GCN Circ. 19335).  The BAT ground-calculated position is
RA, Dec = 319.482, -60.408 deg, which is 
   RA(J2000)  =  21h 17m 55.7s 
   Dec(J2000) = -60d 24' 29.8" 
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 33%.
 
The mask-weighted light curve shows a FRED-like peak starting at ~T-0.5 sec,
peaking at ~T+0.4 sec, and ending at ~T+10 sec.  T90 (15-350 keV) is
6.3 +- 1.0 sec (estimated error including systematics).
 
The time-averaged spectrum from T-1.51 to T+6.63 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.40 +- 0.10.  The fluence in the 15-150 keV band is 1.2 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+0.06 sec in the 15-150 keV band
is 5.1 +- 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/683906/BA/


GRB_name: GRB160424A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19339
SUBJECT: GRB 160424A - XRT position uncertain
DATE:    16/04/25 07:49:42 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:

During the XRT observations of GRB 160424A (Evans et al., GCN Circ. 
19336) the star trackers onboard Swift were unable to acquire a correct 
lock. As a result of this the attitude solution for the spacecraft is 
uncertain, and visual inspection of the images shows that the position 
of the XRT afterglow is highly uncertain. Our best estimate of the 
position is as given in GCN Circ. 19336, however the uncertainty is  ~50 
arc sec.

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


GRB_name: GRB160424A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19340
SUBJECT: GRB 160424A: Fermi GBM observation
DATE:    16/04/25 14:58:14 GMT
FROM:    Hoi-Fung Yu at MPE  <sptfung@mpe.mpg.de>

Hoi-Fung Yu (MPE) reports on behalf of the Fermi GBM Team:

"At 11:49:06.48 UT on 24 April 2016, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 160424A (trigger 483191350 / 160424492),
which was also detected by the Swift (Lien et al. 2016, GCN 19335)
The GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 18 degrees.

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

The GBM light curve shows a single pulse with a duration (T90)
of about 7.6 s (50-300 keV). The time-averaged spectrum from
T0+0.003 s to T0+6.528 s is well fit by a power law function
with an exponential high-energy cutoff. The power law index
is -1.1 +/- 0.1 and the cutoff energy, parameterized as Epeak,
is 220 +/- 30 keV.

The event fluence (10-1000 keV) in this time interval is
(2.6 +/- 0.2)E-06 erg/cm^2. The 1.024-sec peak photon flux measured
starting from T0+0.832 s in the 10-1000 keV band is 7.2 +/- 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: GRB160424A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19342
SUBJECT: Konus-Wind observation of GRB 160424A
DATE:    16/04/25 16:57:26 GMT
FROM:    Anna Kozlova at Ioffe Institute  <ann_kozlova@mail.ioffe.ru>

A. Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline
on behalf of the Konus-Wind team, report:

The long-duration GRB 160424A
(Swift-BAT trigger #683906: Lien et al., GCN Circ. 19335;
Krimm et al., GCN Circ. 19338;
Fermi GBM detection: Hoi-Fung Yu, GCN Circ. 19340)
triggered Konus-Wind at T0=42546.397 s UT (11:49:06.397).

The burst light curve shows a single pulse with a total
duration of ~2.3 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/GRB160424_T42546/

As observed by Konus-Wind, the burst
had a fluence of 1.59(-0.35,+0.60)x10^-6 erg/cm2,
and a 64-ms peak flux, measured from T0+0.464 s,
of 1.71(-0.62,+0.84)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+8.448 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 = -1.24(-0.51,+0.66)
and Ep = 133(-40,+134) keV (chi2 = 58/60 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.0
(chi2 = 57/59 dof)

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


GRB_name: GRB160425A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19343
SUBJECT: GRB 160425A: Swift detection of an unusual burst with an optical afterglow
DATE:    16/04/26 00:05:22 GMT
FROM:    Hans Krimm at NASA-GSFC  <hans.krimm@nasa.gov>

H. A. Krimm (CRESST/GSFC/USRA), A. D'Ai (INAF-IASFPA),
N. Gehrels (NASA/GSFC), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL),
A. Y. Lien (GSFC/UMBC), A. Maselli (INAF-IASFPA), D. M. Palmer (LANL),
J. L. Racusin (NASA/GSFC) and M. H. Siegel (PSU) report on behalf of
the Swift Team:

At 23:26:11 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160425A (trigger=684098).  Swift slewed to the burst
after a short delay due to an observing constraint. 
The BAT on-board calculated location is 
RA, Dec 280.313, -54.359 which is 
   RA(J2000) = 18h 41m 15s
   Dec(J2000) = -54d 21' 33"
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 2 sec, followed by a 
50 second-long peak at T+250s.  There may also be a
precursor peak of ~100 s duration at T-380s. The peak count rate
was ~6000 counts/sec (15-350 keV), at ~0.2 sec after the trigger. 

The XRT began observing the field at 23:29:34.7 UT, 203.4 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 280.3274,
-54.3601 which is equivalent to:
   RA(J2000)  = 18h 41m 18.56s
   Dec(J2000) = -54d 21' 36.2"
with an uncertainty of 2.0 arcseconds (radius, 90% containment). This
location is 30 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 (7.74 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 4.5
(+2.72/-2.31) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 208 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  = 18:41:18.57 = 280.32738
  DEC(J2000) = -54:21:36.1  = -54.36004
with a 90%-confidence error radius of about 0.68 arc sec. This position is 2.6
arc sec. from the center of the XRT error circle. The estimated magnitude is
19.91 with a 1-sigma error of about  0.17. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.06. 

It is extremely unusual for a short GRB to have a long pulse
a few minutes later with much more fluence. 
It is more common for a long GRB to have a short precursor pulse. 
Further characterization of this event will require the full
downlinked data set. 

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: GRB160425A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19344
SUBJECT: GRB 160425A : MASTER earlier optical observations
DATE:    16/04/26 00:25:58 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
Lomonosov Moscow State University, Sternberg Astronomical Institute

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

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

A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov
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)

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 SAAO was pointed to the  GRB 160425A (trigger time 23:26:11.34) 
at 2016-04-25 23:28:59UT.
On our first (30s, t_start=2016-04-25 23:28:59UT, m_lim=17.3, 
polarization)  exposition there is 
marginally seen optical transient  within 
SWIFT error-box up (H. A. Krimm et al., GCN #19343) at 
RA=280.32738,-54.36004

The observations will be continued.


GRB_name: GRB160422A
Detection_method: CALET
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19345
SUBJECT: GRB 160422A: CALET Gamma-Ray Burst Monitor detection
DATE:    16/04/26 01:27:37 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto@phys.aoyama.ac.jp>

S. Ricciarini (U of Florence), A. Yoshida, T. Sakamoto, Y. Kawakubo, M. Moriyama, 
Y. Yamada (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), I. Takahashi (IPMU), 
Y. Asaoka, S. Ozawa, S. Torii (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), 
W. Ishizaki (ICRR), M. L. Cherry (LSU), P. S. Marrocchesi (U of Siena) 
and the CALET collaboration:

The long-duration GRB 160422A (Burns et al., GCN circ. 19331; Yassine et al., 
GCN circ. 19329; INTEGRAL-ACS #7450) triggered the CALET Gamma-Ray Burst Monitor (CGBM) 
at 11:59:08.28 on 22 April 2016.  The burst signal was only seen by the SGM instrument.  
This fact is consistent that the GRB location of the Fermi-LAT (Yassine et al., 
GCN circ. 19329) was outside the field of view of the CALET CALorimeter (CAL) instrument, 
which has the capability to observe gamma-rays above 1 GeV, at the trigger time.  
The boresight angle of the SGM to the Fermi-LAT position was ~105 deg.  

The light curve of the SGM shows at least two episodes.  The first episode starts at 
T0-7 sec, peaks at T0-6 sec and ends at T0-4 sec.  The second episode shows the emission 
starting at T0, peaking at T0+1 sec and ending at T0+4 sec.  The T90 duration measured by 
the SGM data is 8.7 +- 0.3 sec (100-1000 keV). 

The CGBM data used in this analysis are provided by the Waseda CALET Operation Center 
located at the Waseda University.


GRB_name: GRB160422A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19346
SUBJECT: GRB 160422A: Swift/UVOT Afterglow Confirmation
DATE:    16/04/26 02:00:23 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 160422A
32624 s after the LAT trigger (Yassine et al., GCN Circ. 19329).
The optical afterglow candidate (Marshall, GCN Circ. 19333)
has faded in a later observation in the same filter.
Its positional consistency with the  XRT source
(Maselli et al. GCN Circ. 19334) and its fadiing
behavior confirm that it is the optical afterglow of GRB 160422A.

The preliminary UVOT position is:
    RA  (J2000) =  02:48:22.78 =  42.09493 (deg.)
    Dec (J2000) = -57:52:30.4  = -57.87512 (deg.)
with an estimated uncertainty of 0.45 arc sec. (radius, 90% confidence).

Preliminary detections 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            33427        34064          627         19.50  0.05
white            44903        44701          785         19.91  0.06
v                39970        45820          320         19.29  0.23
u                32624        33420          783         19.09  0.10

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: GRB160425A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19347
SUBJECT: GRB 160425A: Enhanced Swift-XRT position
DATE:    16/04/26 04:29:14 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 1763 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 160425A, 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 = 280.32719, -54.36001 which is equivalent
to:

RA (J2000): 18h 41m 18.53s
Dec (J2000): -54d 21' 36.0"

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: GRB160425A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19348
SUBJECT: GRB 160425A: Swift-XRT refined Analysis
DATE:    16/04/26 07:23:07 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 H.A. Krimm report on behalf of the Swift-XRT team:

We have analysed 7.0 ks of XRT data for GRB 160425A (Krimm et al. GCN
Circ. 19343), from 207 s to 18.4 ks after the  BAT trigger. The data
comprise 439 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Beardmore et al. (GCN Circ. 19347).

The late-time light curve (from T0+6.1 ks) can be modelled with a
power-law decay with a decay index of alpha=0.78 (+/-0.23).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.18 (+/-0.04). The
best-fitting absorption column is  5.26 (+0.23, -0.22) 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 2.76 (+0.19, -0.18)
and a best-fitting absorption column of 5.7 (+/-0.8) x 10^21 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 2.9 x 10^-11 (9.0 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      5.7 (+/-0.8) x 10^21 cm^-2
Galactic foreground: 7.7 x 10^20 cm^-2
Excess significance: 10.6 sigma
Photon index:      2.76 (+0.19, -0.18)

If the light curve continues to decay with a power-law decay index of
0.78, the count rate at T+24 hours will be 0.019 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.5 x
10^-13 (1.7 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/00684098.

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


GRB_name: GRB160425A
Detection_method: GROND
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19349
SUBJECT: GRB 160425A: GROND observation
DATE:    16/04/26 09:20:09 GMT
FROM:    Jochen Greiner at MPI  <jcg@mpe.mpg.de>

J. Bodensteiner (MPE Garching), S. Schmidl (TLS Tautenburg), and 
J. Greiner (MPE Garching) report on behalf of the GROND team:
  
We observed the field of GRB 160425A (Swift trigger 684098; Krimm et al.
GCN Circ. 19343) 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 04:38 UT on April 26, 2016, 5.2 hrs after the GRB
trigger. They were performed at an average seeing of 3.1" and at an
average airmass of 1.2.
  
We detect an optical source at the position reported by  Krimm et al.
(GCN 19343) and Lipunov et al. (GCN 19344).
  
Based on total exposures of 24 minutes in g'r'i'z' and 20 minutes in  
JHK, at a midtime of 7.16 hrs after the burst, we measure the following
preliminary magnitudes and upper limits (AB magnitude system):
  
g' = 22.2 +/- 0.3 mag,         
r' = 21.1 +/- 0.2 mag,
i' = 20.7 +/- 0.2 mag,
z' = 20.5 +/- 0.1 mag,
J  = 19.7 +/- 0.2 mag,         
H  = 19.4 +/- 0.3 mag, and
K  > 18.3 mag. 
  
The magnitudes and upper limits are calibrated against GROND zeropoints
and 2MASS field stars and are not corrected for the Galactic foreground
extinction corresponding to a reddening of E_(B-V)= 0.06 mag in the 
direction of the burst (Schlegel et al. 1998).
  
Relative to the UVOT and MASTER reports, the source has faded, though
we do not detect significant fading in our data so far (strongly mitigated
by the bad conditions). We therefore cannot distinguish between afterglow
or host flux.


GRB_name: GRB160425A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19350
SUBJECT: GRB 160425A VLT/X-shooter redshift
DATE:    16/04/26 09:28:42 GMT
FROM:    Nial Tanvir at U.Leicester  <nrt3@star.le.ac.uk>

N. R. Tanvir (U. Leicester), D. Xu (NAO/CAS), T. Kruehler (MPE),
D. Malesani, J. P. U. Fynbo (DARK/NBI), G. Pugliese (U. Amsterdam),
A. J. Levan (U. Warwick), Z. Cano (U. Iceland) report on behalf
of a larger collaboration:

We observed the optical counterpart of the unusual
GRB 160425A (Krimm et al., GCN 19343) with the
ESO Very Large Telescope UT 2 (Kueyen) equipped
with the X-shooter spectrograph, covering the wavelength
range 3500-20000 AA.  Observations started on April 26.26 UT
(approx 6.9 hr after the GRB) and consisted of 4 exposures of
1200 s each.

In our acquisition images, we detect an extended object
consistent with the position of the UVOT counterpart,
whose morphology exhibits two knots separated by ~1.2". 
That object is faintly visible in the digitized sky survey, 
and is likely the host galaxy of GRB 160425A.

The spectrum reveals two distinct systems at z=0.555, based 
on emission lines of Halpha, Hbeta, [O III], [O II] and [S III].  
The velocity separation between them is ~180 km/s, and the 
spatial separation is consistent with the two knots seen in
the imaging (corresponding to ~8 kpc at this distance), 
suggesting an interacting pair of galaxies. 

We acknowledge expert support from the ESO observing staff, 
particularly Jose Velazquez and Juan Carlos Munoz, in obtaining 
these observations.


GRB_name: GRB160425A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19351
SUBJECT: GRB 160425A MASTER notices: possible host galaxy in the optical error-box
DATE:    16/04/26 10:45:15 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

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

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

MASTER-SAAO telescope  pointed to the unusual short GRB160425A (Krimm et 
al. GCN #19343 ) at 2016-04-25 23:28:59UT 168s after trigger time, 30s first expositions with orthogonal polarimeter filters .
The delay is caused with the short rain, the roof was closed at the trigger time.

MASTER-SAAO auto-detection system discovered OT source at (RA, Dec) = 280.32738,-54.36004
at the first 30s polarized image in 1 tube at  2016-04-25 23:28:59UT with  unfiltered m_OT~18.2+-0.5
(w=0.2B+0.8R calibrated by USNO-B1) http://observ.pereplet.ru/images/MASTERGRB160425A.jpg . 
The second tube in orthogonal polarization filter doesn't see it with 
m_lim=17.7, possibly it depends on polarization of this source.

There is a faint optical source at the Palomar (POSS) both red and blue images. 
But this source doesn't present at USNO-B1 catalogue. There is blue source 
(in  0.411") in GSC2.3.2 with jmag=22.16.
The most probable classification of it is the host galaxy of  short  GRB160425A.

SWIFT UVOT see optical afterglow 19.9m in white filter (150s expos., 
starting 208 seconds after the BAT trigger (23:26:11UT) (Krimm et 
al., GCN Circ. 19343) and  GROND see  afetrglow in g'r'i'z' started at 
04:38 UT on April 26, 2016, 5.2 hrs after the GRB (Bodensteiner et al., 
GCN Circ. 19349).

The analyses will be continued.


GRB_name: GRB160422A
Detection_method: GROND
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19352
SUBJECT: GRB 160422A: GROND NIR afterglow detection
DATE:    16/04/26 11:17:40 GMT
FROM:    Jan Bolmer at MPE/Garching  <jan@bolmer.de>

T. Schweyer, J. Bolmer, J. Greiner (all MPE Garching), and D. A. Kann
(TLS Tautenburg) report on behalf of the GROND team:

We observed the field of GRB 160422A (Fermi/GBM trigger 483019143;
Yassine et al., GCN #19329) 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 23:02 UT on 22-04-2016, 11.06 hrs after the
GRB trigger. They were performed at an average seeing of 2.0" and at
an average airmass of 2.2, but also through thick cirrus, which
prevented proper measurements in g'r'i'z'.

We found a single point source coincident with the 0.45" Swift-UVOT
error circle reported by Marshall et al. (GCN #19333).

Based on the first 4 min of total exposures in JHK, we estimate
preliminary magnitudes (all in AB system) of

J = 17.9 +/- 0.3 mag,
H = 17.4 +/- 0.3 mag, and
K > 17.0 mag.

Given magnitudes are calibrated against 2MASS field stars and are not
corrected for the expected Galactic foreground extinction
corresponding to a reddening of E_(B-V)=0.02 mag in the direction of
the burst (Schlafly & Finkbeiner 2011).


GRB_name: GRB160325A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19353
SUBJECT: GRB 160325A: Skynet PROMPT-CTIO observations of the optical afterglow
DATE:    16/04/26 14:02:12 GMT
FROM:    Adam S. Trotter at UNC-Chapel Hill/PROMPT/Skynet  <atrotter@physics.unc.edu>

A. Trotter, D. Reichart, J. Haislip, J. Moore, N. Frank, M. Maples, E. Johnson, R. Joyner, J. Martin, C. Salemi, J. A. Crain, K. Ivarsen, A. LaCluyze, and M. Nysewander report:

Skynet observed the Swift BAT/XRT localization of GRB 160325A (Sonbas et al., GCN 19222, Swift trigger=680436) with with two 16" telescopes (P5, P6) and one 24" telescope (P1) of the PROMPT array at CTIO, Chile. Starting at 2016-03-25 07:01:44 UT and continuing until 09:55 UT (t=100s-2.9h post-trigger), Skynet took a total of 211 exposures ranging from 10-160s in the V band (P6) and the I band (P1,P5).

We clearly detected a fading optical afterglow at the position first reported by Fugazza & Melandri (GCN 19223). 

A preliminary light curve is at:
http://www.skynet.unc.edu/grb/grb160325a.png

Magnitudes are in the Vega System, calibrated to 4 APASS DR9 stars in the field.  Magnitudes have not been corrected for line-of-sight Milky Way dust extinction, with expected E(B-V)=0.12 (Schlafly & Finkbeiner 2011).

No further Skynet observations are scheduled.


GRB_name: GRB160425A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19354
SUBJECT: GRB 160425A: SMARTS optical/IR observations
DATE:    16/04/26 20:51:10 GMT
FROM:    Bethany Cobb at GWU  <bcobb@gwu.edu>

B. E. Cobb (GWU), reports:

Using the ANDICAM instrument on the 1.3m telescope at CTIO, we obtained
optical/IR imaging of the error region of GRB 160425A (GCN 19343,
Krimm et al.) at two epochs. For each epoch, total summed exposure times
amounted to 15 minutes in I and V and 12 minutes in J and K.

No source is detected at the position of the optical
afterglow (e.g. GCN 19343, Krimm et al.; GCN 19344, Lipunov
et al.; GCN 19349, Bodensteiner et al.) to the approximate limiting
magnitudes listed below. The first epoch was obtained under particularly
poor seeing conditions.

mid-exposure               mid-exposure time
time                              post-burst
 limits
2016-04-26 04:53 UT  5.44083 hours      I > 19.5   J > 16.6   K > 15.7

2016-04-26 08:29 UT  9.04250 hours      I > 19.9   J > 17.9   K > 17.1

Magnitudes are calibrated using USNO-B1.0 stars in I, and
2MASS stars in J and K.


GRB_name: GRB160425A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19355
SUBJECT: GRB 160425A: Swift-BAT refined analysis
DATE:    16/04/26 21:41:42 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@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),
J. P. Norris (BSU), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU),
E. Troja (NASA/GSFC/UMCP), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

Using the data set from T-240 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 160425A (trigger #684098)
(Krimm, et al. GCN Circ. 19343).  The BAT ground-calculated position is
RA, Dec = 280.339, -54.343 deg which is
  RA(J2000)  =  18h 41m 21.5s
  Dec(J2000) = -54d 20' 34.6"
with an uncertainty of 3.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 71%.

The mask-weighted light curve shows several separate pulses. The first short pulse
starts at ~ T-0.5 s, peaks at ~T+0.2 s, and ends at ~T+1.5 s. The second pulse
occurs at ~T+60 s and is quite weak. Another strong pulse starts at ~T+250 s, peaks
at ~T+270 s, and ends at ~ T+300 s. T90 (15-350 keV) is 304.58 +- 15.04 sec
(estimated error including systematics). The potential precursor peak seen in the
raw light curve at ~T-380 s (Krimm, et al., GCN Circ. 19343) is due to a noisy
detector.

The time-averaged spectrum from T-0.53 to T+319.80 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
2.20 +- 0.18. The fluence in the 15-150 keV band is 2.1 +- 0.2 x 10^-6 erg/cm2.
The total fluence is dominated by the pulse at ~T+270 s, which has a fluence of
1.1 +/- 0.1 x 10^-6 erg/cm2, while the fluence of the short pulse is
2.8 +/- 0.2 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from
T-0.27 sec in the 15-150 keV band is 2.8 +- 0.2 ph/cm2/sec. All the quoted errors
are at the 90% confidence level.

The spectrum of the initial short pulse is best-fitted by a simple power-law model
with a power-law index of 1.71 +/- 0.14. This value is a typical number for a long
GRB, but is also consistent with the majority of the short GRB population
(Sakamoto et al. 2011).

Using a 32-ms binned light curve, the lag analysis of the initial short pulse
is 57 (-27, +34) ms for the 100-350 keV to 25-50 keV, and 19 (-38, +32) ms for
the 50-100 keV to 15-25 keV band. These numbers are consistent with
those of a long GRB. However, we note that the low redshift (z=0.555, Tanvir et al,
GCN Circ. 19350) indicates that this GRB might have a lower luminosity
(the luminosity of the short pulse in the BAT observed energy band, 15-150 keV,
is ~ 1.7 x 10^50 erg/s), and thus the this GRB might lie outside the usual
lag-luminosity relation (Norris et al. 2000).

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/684098/BA/


GRB_name: GRB160425A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19356
SUBJECT: GRB 160425A: Skynet PROMPT-CTIO observations of the optical afterglow
DATE:    16/04/27 18:54:26 GMT
FROM:    Adam S. Trotter at UNC-Chapel Hill/PROMPT/Skynet  <atrotter@physics.unc.edu>

A. Trotter, D. Reichart, J. Haislip, J. Moore, N. Frank, M. Maples, E. Johnson, R. Joyner, J. Martin, C. Salemi, J. A. Crain, K. Ivarsen, A. LaCluyze, and M. Nysewander report:

Skynet observed the Swift BAT/XRT localization of the unusual GRB 160425A (Krimm et al., GCN 19343, Swift trigger=684098) with with two 16" telescopes (P5, P6), and twp 24" telescopes (P1, P8) of the PROMPT array at CTIO, Chile. Starting at 2016-04-25 01:34 UT and continuing until 10:14 UT (t=2.1-10.8h post-trigger), Skynet took a total of 849 160s exposures in the I band (P1, P5), V band (P6) and B band (P8).  

We detect a fading optical afterglow in I-band images at the UVOT position reported by Krimm et al. (GCN 19343), with I~17 at t=2.2h and I~20 at t=7.3h. 

A preliminary light curve is at:
http://www.skynet.unc.edu/grb/grb160425a.png

Preliminary magnitudes are in the Vega System, calibrated to 8 APASS DR9 stars in the field.  Magnitudes have not been corrected for line-of-sight Milky Way dust extinction, with expected E(B-V)=0.05 (Schlafly & Finkbeiner 2011).

No further Skynet observations are scheduled.


GRB_name: GRB160425A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19357
SUBJECT: GRB 160425A: Swift/UVOT Detection
DATE:    16/04/27 20:10:02 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <siegel@swift.psu.edu>

M. H. Siegel (PSU) 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 160425A
208 s after the BAT trigger (Krimm et al., GCN Circ. 19343).
A fading source consistent with the XRT position (Beardmore et al. GCN Circ. 19347)
is detected in the initial UVOT exposures.  This source is consistent
with the optical transient reported by MASTER (Lipunov et al, GCN Circ. 19344)
and  GROND (Bodensteiner et al., GCN Circ. 19349). The source has plateaud over
the last day, which may indicate detection of the host galaxy reported
by MASTER (Balanutsa et al., GCN Circ. 19351).

The preliminary UVOT position is:
   RA  (J2000) =  18:41:18.58 = 280.32743 (deg.)
   Dec (J2000) = -54:21:36.3  = -54.36007 (deg.)
with an estimated uncertainty of 0.53 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)         208          358          147         19.57 +/- 0.10
white              859         1009          147         20.70 +/- 0.35
white             1164         2397          155        >20.19
white             6727         8221          254        >20.79
white            11858        12765          885         21.03 +/- 0.19
white            35282        41433         2162         21.48 +/- 0.23
white            46310        58620         3898         21.48 +/- 0.16
white           104099       111153         2061         21.80 +/- 0.30
v                  365         2447          233         19.22 +/- 0.31
b                  465         1852          156         20.16 +/- 0.32
u                  440         6517          410         20.07 +/- 0.26
w1                 415         7748          607         20.24 +/- 0.30
m2                 390         7542          430        >19.7
w2                 515        13672         1296        >20.8

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.06 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB160425A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19358
SUBJECT: LSGT observation of GRB 160425A
DATE:    16/04/28 07:59:24 GMT
FROM:    Changsu Choi at Seoul Nat U  <changsu@astro.snu.ac.kr>

Changsu Choi and Myungshin Im (CEOU/SNU)

We observed the field of GRB 160425A (Krimm et al. GCN Circ. 19343) using
LSGT(Lee Sang Gak Telescope; Im et al. 2015, JKAS, 48, 207 ). Images were
taken in R and I band starting on Apr. 26 15:14:22 UT(~15.24 hr after
burst). We do not detect the optical afterglow candidate within the XRT
enhanced error circle (Beardmore et al. GCN Circ. 19347) to the approximate
limiting magnitudes listed below.

mid-time(UT)                    post-bust-hour    exposure(s)
filter(limiting mag)
-----------------------------------------------------------------------------------------------------------

2016-04-26 16:10:02        16.16722                2700                   R
> 19.55
2016-04-26 17:04:26        17.07396                2700
I   > 19.22


Magnitudes are calibrated using USNO-B1 stars in R1 and I.


GRB_name: GRB160422A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19359
SUBJECT: GRB 160422A: XRT Afterglow Confirmation
DATE:    16/04/28 13:38:27 GMT
FROM:    Alessandro Maselli at INAF/IASF Palermo  <maselli@ifc.inaf.it>

A. Maselli (INAF-IASFPA), D. Malesani (DARK/NBI), K.L. Page 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-detected burst GRB 160422A (Yassine et al., GCN Circ. 19329; Burns 
et al., GCN Circ. 19331), extending from T0+400 ks to T0+470 ks after 
the Fermi/GBM trigger.

At the position of the candidate afterglow reported by Maselli et al. 
(GCN Circ. 19334) no source is detected in the new observation, with a 
three sigma upper limit of 2.6e-3 ct/s. This confirms that it was the 
X-ray afterglow of GRB 160422A.

The results of the full analysis of the XRT observations are available 
at http://www.swift.ac.uk/xrt_products/00020605

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


GRB_name: GRB160501A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19365
SUBJECT: GRB 160501A: Swift detection of a burst
DATE:    16/05/01 00:58:55 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

J. R. Cummings (NASA/UMBC), A. P. Beardmore (U Leicester),
J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL), T. Sakamoto (AGU),
M. H. Siegel (PSU) and T. N. Ukwatta (LANL) report on behalf of the
Swift Team:

At 00:40:31 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160501A (trigger=684679).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 286.377, -17.240 which is 
   RA(J2000) = 19h 05m 30s
   Dec(J2000) = -17d 14' 22"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is usual for an image trigger, there
is no clear variation visible in the immediately-available lightcurve
data. 

The XRT began observing the field at 00:42:39.8 UT, 128.1 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source located at RA, Dec 286.38344,
-17.24088 which is equivalent to:
   RA(J2000)  = 19h 05m 32.03s
   Dec(J2000) = -17d 14' 27.2"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 22 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 (1.62 x
10^21 cm^-2, Willingale et al. 2013), with an excess column of 2.7
(+3.06/-2.65) x 10^21 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 1.08e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 136 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 upper limit is 19.6 magnitude. 
The 8'x8' region for the list of sources generated on-board covers
100% of the XRT error circle. The typical upper limit is 18.0. 
No correction has been made for the expected extinction corresponding
to E(B-V) of 0.18. 

Burst Advocate for this burst is J. R. Cummings (jayc 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: GRB160501A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19366
SUBJECT: GRB 160501A: NOT optical and NIR observations
DATE:    16/05/01 03:55:51 GMT
FROM:    Zach Cano at U of Iceland  <zewcano@gmail.com>

Z. Cano (Univ. Iceland), N. Tanvir (Univ. Leicester), D. Malesani
(DARK/NBI)  & J. Saario (NOT) report on behalf of a larger collaboration:

We observed the field of GRB 160501A (Cummings et al.; GCN Circ. 19365)
with the 2.5-m Nordic Optical Telescope equipped with the StanCam and the
NOTCam, starting at 01:57 UT on 01 May 2016.  We obtained 15 minutes in the
I-band (StanCam) and 18 minutes in the H-band (NOTCam).  In our co-added
optical and NIR images we do not detect any new source within the XRT error
circle to the following limits:

I > 22.3 mag
H > 19.0 mag

These upper limits (Vega) are for a single point source in the GRB field,
they are calibrated against the USNO-B1 (optical) and 2MASS (NIR)
catalogues, and they have not been corrected for foreground extinction.


GRB_name: GRB160501A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19367
SUBJECT: GRB 160501A MASTER-NET early observations
DATE:    16/05/01 09:23:39 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,
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.Senik
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)

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 SAAO was pointed to the  GRB160501A 24 sec after notice time 
and 106 sec after trigger time at 2016-05-01 00:42:21 UT in two 
polarizations. On our first (20s exposure)  set we haven't found optical 
transient  within SWIFT error-box (Cummings et al GCN 19365).
The 5-sigma upper limit has been about 17.5 mag  on single (20 s exposure) 
and   19.1 mag  at coadd of first 10 images (with total exposure 780 s).
Not very depth upper limits are explained by the proximity to the Moon.
The message may be cited.


GRB_name: GRB160501A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19368
SUBJECT: GRB 160501A: TAROT Calern observatory optical observations
DATE:    16/05/01 10:13:48 GMT
FROM:    Alain Klotz at IRAP-CNRS-OMP  <Alain.Klotz@free.fr>

Klotz A., Turpin D., Atteia J.L. (CNRS-OMP-IRAP),
Boer, M., Laugier, R. (CNRS-ARTEMIS),
Gendre B. (UVI - Etelman Obs.) report:

We imaged the field of GRB 160501A detected by SWIFT
(trigger 684679) with the TAROT robotic telescope (D=25cm)
located at the Calern observatory, France.

The observations started 50 min after the GRB trigger.
The elevation of the field increased from
20 degrees above horizon and weather conditions
were good.

We co added images to increase detectivity:

t1(s) t2(s)  Rmag_lim  Site
3594  5526   18.5      TAROT Calern
5526  7863   18.5      TAROT Calern

Magnitudes were estimated with the nearby USNO-B1 stars
and are not corrected for galactic dust extinction.

N.B. Galactic coordinates are lon= 18.9676 lat=-10.7948
and the galactic extinction in R band is about 1.0 magnitudes
estimated from D. Schlegel et al. 1998ApJ...500..525S.


GRB_name: GRB160501A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19369
SUBJECT: GRB 160501A: Enhanced Swift-XRT position
DATE:    16/05/01 15:20:19 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 2151 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 160501A, 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 = 286.38402, -17.24138 which is equivalent
to:

RA (J2000): 19h 05m 32.16s
Dec (J2000): -17d 14' 29.0"

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: GRB160501A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19370
SUBJECT: GRB 160501A: RATIR Optical and NIR Observations 
DATE:    16/05/01 15:45:08 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 (STScI), J.
Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara
(GSFC/STScI), 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 160501A (Cummings et al., GCN Circ. 19365)
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 2016/05 1.33 to
2016/05 1.47 UTC (7.23 to 10.70 hours after the BAT trigger), obtaining
a total of 1.73 hours exposure in the r and i bands and 0.66 hours
exposure in the Z, Y, J, and H bands.

For a source within the enhanced Swift-XRT error circle (Evans et al.,
GCN Circ. 19369), in comparison with the USNO-B1 and 2MASS catalogs, we
obtain the following 3-sigma upper limits:

 r > 22.94
 i > 22.76
 Z > 21.69
 Y > 21.22
 J > 20.81
 H > 19.90

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 AstronÃ³mico Nacional in San Pedro
MÃ¡rtir.


GRB_name: GRB160501A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19371
SUBJECT: GRB 160501A: Swift-XRT refined Analysis
DATE:    16/05/01 17:34:09 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 J.R. Cummings report on behalf of the Swift-XRT team:

We have analysed 6.8 ks of XRT data for GRB 160501A (Cummings et al.
GCN Circ. 19365), from 118 s to 46.0 ks after the  BAT trigger. The
data comprise 161 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. 19369).

The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=2.76 (+/-0.16). At T+261 s  the decay
steepens to an alpha of 4.4 (+0.6, -0.3) before breaking again at T+918
s to a final decay with index alpha=0.26 (+0.36, -0.20).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.96 (+0.16, -0.15). The
best-fitting absorption column is  2.9 (+/-0.4) x 10^21 cm^-2, in
excess of the Galactic value of 1.6 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 2.06 (+0.25, -0.18)
and a best-fitting absorption column consistent with the Galactic
value. The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 3.4 x 10^-11 (4.6 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      1.6 (+0.7, -0.0) x 10^21 cm^-2
Galactic foreground: 1.6 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:      2.06 (+0.25, -0.18)

If the light curve continues to decay with a power-law decay index of
0.26, the count rate at T+24 hours will be 7.9 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.7 x
10^-13 (3.6 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/00684679.

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


GRB_name: GRB160501A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19372
SUBJECT: GRB 160501A: Swift/UVOT Upper Limits
DATE:    16/05/01 20:00:06 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld@ucl.ac.uk>

A. A. Breeveld (UCL-MSSL) and J. R. Cummings (NASA/UMBC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 160501A
136s after the BAT trigger (Cummings et al., GCN Circ. 19365).
No optical afterglow consistent with the XRT position (Evans et al. GCN 
Circ. 19369) 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           136          286          147         >20.3
u_FC               295          544          246         >19.7
white              575         1543          245         >21.1
v                  625         1594          117         >18.9
b                  551         1518           97         >19.9
w1                 674         1643          117         >19.2
m2                 649         1618          117         >19.7
w2                 600         1569          117         >19.2

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.18 in the direction of the 
burst (Schlegel et al. 1998).


GRB_name: GRB160501A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19373
SUBJECT: GRB 160501A: UKIRT near-IR upper limits
DATE:    16/05/01 22:03:31 GMT
FROM:    Wen-fai Fong at U of Arizona  <wfong@email.arizona.edu>

W. Fong and P. Milne (University of Arizona) report:

"We observed the field of GRB 160501A (Cummings et al., GCN 19365) with the
Wide Field Camera (WFCAM) mounted on the 3.8-m United Kingdom Infrared
Telescope (UKIRT) on Mauna Kea beginning on 2016 May 1.533 UT (12.1 hr
post-burst). We obtained observations in the J- and K-bands in 0.75"
seeing. Using the quick-look pipeline ORAC-DR, we do not detect any near-IR
source in or around enhanced X-ray position (Evans et al., GCN 19369).
Calibrated to 2MASS, we therefore place 3-sigma limits of J(AB)>19.7 mag
and K(AB)>19.2 mag on the near-IR afterglow of GRB 160501A at 12.1 hr
post-burst. We note that this analysis is preliminary and a final reduction
of the images are expected to be at least ~1.5 mag deeper.

We thank Tim Carroll, Watson Varricatt and Tom Kerr for their assistance in
planning and executing these observations."


GRB_name: GRB160501A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19374
SUBJECT: GRB 160501A: MITSuME Okayama upper limits
DATE:    16/05/02 00:56:20 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 160501A (Cummings et al., GCNC 19365)
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 2016-05-01 17:18:31 UT (~16.6 h after
the burst). We did not find any new point source within the enhanced
XRT circle (Evans et al., GCNC 19369) 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
-----------------------------------------------------
0.73280    18:15:45    5460.0   >19.4  >19.1  >18.3
-----------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]


GRB_name: GRB160501A
Detection_method: GROND
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19375
SUBJECT: GRB 160501A: GROND Upper limits
DATE:    16/05/02 10:01:04 GMT
FROM:    Fabian Knust at MPE/GROND  <fknust@mpe.mpg.de>

J. Bodensteiner, F. Knust, T. Schweyer , J. Greiner (all MPE Garching)
report on behalf of the GROND team:

We observed the field of GRB 160501A (Swift trigger 684679;  Cummings et
al., GCN #19365) 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 07:15 UT on 2016-05-01, 6h 35min after the GRB
trigger. They were performed at an average seeing of 1.3" and at an
average airmass of 1.09.

We do not detect a source within the Swift-XRT error circle reported by
Evans et al. (GCN #19369) down to

g' > 24.8 mag,
r' > 24.5 mag,
i' > 23.8 mag,
z' > 23.9 mag,
J > 21.1 mag,
H > 20.7 mag, and
K > 19.1 mag.
(all in AB).

The given limits are derived based on calibration against GROND zeropoints
and 2MASS field stars and are not corrected for the Galactic foreground
extinction corresponding to a reddening of E_(B-V)= 0.18 mag in the
direction of the burst (Schlegel et al. 1998).


GRB_name: GRB160501A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19376
SUBJECT: GRB 160501A: Swift-BAT refined analysis
DATE:    16/05/02 13:46:06 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto@phys.aoyama.ac.jp>

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),
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 160501A (trigger #684679)
(Cummings, et al., GCN Circ. 19365).  The BAT ground-calculated position is
RA, Dec = 286.389, -17.249 deg which is 
   RA(J2000)  =  19h 05m 33.2s 
   Dec(J2000) = -17d 14' 54.8" 
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 81%.
 
The mask-weighted light curve a broad peak starting from T-80 sec, peaking 
at T+50 sec and ending at T+90 sec.  T90 (15-350 keV) is 118 +- 19 sec 
(estimated error including systematics).
 
The time-averaged spectrum from T-54.3 to T+72.6 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 0.6 +- 1.3, 
and Epeak of 28 +- 9 keV (chi squared 54.26 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 9.5 +- 1.3 x 10^-7 erg/cm2
and the 1-sec peak flux measured from T-54.38 sec in the 15-150 keV band is
0.5 +- 0.2 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 2.4 +- 0.2 (chi squared 63.09 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/684679/BA/


GRB_name: GRB160501A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19378
SUBJECT: GRB 160501A: SMARTS optical/IR observations
DATE:    16/05/03 15:18:43 GMT
FROM:    Bethany Cobb at GWU  <bcobb@gwu.edu>

B. E. Cobb (GWU) reports:

Using the ANDICAM instrument on the 1.3m telescope at CTIO, we
obtained optical/IR imaging of the error region of GRB 160501A
(GCN 19365, Cummings et al.) with a mid-exposure time of 4.3 hours
post-burst (2016-05-01 05:01 UT). Total summed exposure times
amounted to 36 minutes in I and 30 minutes in J.

No source is detected at the position of the X-ray
afterglow (GCN 19365, Cummings et al; GCN 19369, Evans
et al.) to approximate limiting magnitudes of I > 20.7 and J > 18.5.
Magnitudes are calibrated using USNO-B1.0 stars in I,
and 2MASS stars in J.


GRB_name: GRB160503A
Detection_method: Fermi LAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19379
SUBJECT: GRB 160503A: Fermi-LAT detection
DATE:    16/05/04 03:08:19 GMT
FROM:    Nicola Omodei at Stanford U.  <nicola.omodei@slac.stanford.edu>

N. Omodei, G. Vianello (Stanford), J. Racusin (GSFC), E. Bissaldi (INFN 
Bari)

report on behalf of the Fermi-LAT team:

The Fermi-LAT detected high-energy emission from GRB 160503A which 
triggered the Fermi-GBM at 13:36:32.01 on May, 03, 2016 (trigger 
483975395 / 160503567).

The best LAT on-ground location is found to be:

RA, Dec = 0.54, -1.93 (degrees, J2000) with an error radius of 0.52 deg 
(90 % containment, statistical error only).

This was 25 deg from the LAT boresight at the time of the trigger. The 
event is faint and soft, but detected over a long time scale (10 ks). No 
events at GeV energies and above have been observed.
A Swift ToO has been requested for this burst.
The Fermi-LAT point of contact for this burst is Elisabetta Bissaldi 
(elisabetta.bissaldi@ba.infn.it).

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: GRB160503A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19380
SUBJECT: GRB 160503A: Fermi GBM observation
DATE:    16/05/04 12:34:06 GMT
FROM:    Kilian Toelge at MPE  <tkili@mpe.mpg.de>

B. Mailyan (UAH) and K. Toelge (MPE)
report on behalf of the Fermi GBM Team:

"At 13:36:32.008 UT on 03 May 2016, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 160503A (trigger 483975396 / 160503567), which 
was also detected by the LAT
(N. Omodei et al. 2016, GCN 19379)
The GBM on-ground location is consistent with the LAT position.

The angle from the Fermi LAT boresight at the GBM trigger time is 25 
degrees.

The GBM light curve consists of two peaks
with a duration (T90) of about 59.4 s (50-300 keV).
The time-averaged spectrum from T0-4.9 s to T0+28.9 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -1.28 +/- 0.14 and
the cutoff energy, parameterized as Epeak, is 138.7 +/- 33.5 keV.

The event fluence (10-1000 keV) in this time interval is
(2.15 +/- 0.25)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-0.58 s in the 8-1000 keV band
is 2.5 +/- 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: GRB160504A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19382
SUBJECT: GRB 160504A: Swift detection of a burst
DATE:    16/05/04 19:46:00 GMT
FROM:    Jamie A. Kennea at PSU/Swift-XRT  <kennea@swift.psu.edu>

D. Malesani (DARK/NBI), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC),
D. M. Palmer (LANL), T. G. R. Roegiers (PSU),
B. Sbarufatti (INAF-OAB/PSU) and T. N. Ukwatta (LANL) report on behalf
of the Swift Team:

At 19:30:37 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160504A (trigger=685124).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 170.043, +55.997 which is 
   RA(J2000) = 11h 20m 10s
   Dec(J2000) = +55d 59' 48"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex
structure with a duration of about 10 sec.  The peak count rate
was ~1300 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 19:32:46.0 UT, 128.7 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 170.07309, 56.00016 which is equivalent
to:
   RA(J2000)  = 11h 20m 17.54s
   Dec(J2000) = +56d 00' 00.6"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 61 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 8.12
x 10^19 cm^-2 (Willingale et al. 2013). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 98 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 none of
the XRT error circle. 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 D. Malesani (malesani AT dark-cosmology.dk). 
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: GRB160504A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19383
SUBJECT: GRB 160504A: TAROT Calern observatory optical observations
DATE:    16/05/04 20:02:56 GMT
FROM:    Alain Klotz at IRAP-CNRS-OMP  <Alain.Klotz@free.fr>

Klotz A., Turpin D., Atteia J.L. (CNRS-OMP-IRAP),
Boer, M., Laugier, R. (CNRS-ARTEMIS),
Gendre B. (UVI - Etelman Obs.) report:

We imaged the field of GRB 160504A detected by SWIFT
(trigger 685124) with the TAROT robotic telescope (D=25cm)
located at the Calern observatory, France.

The observations started 57.1s after the GRB trigger
(16.5s after the notice). The elevation of the field increased from
77 degrees above horizon and weather conditions
were good but during twilight.

The first image is trailed with a duration of 60.0s
(see the description in Klotz et al., 2006, A&A 451, L39).
We do not detect any OT with a limiting magnitude of:
t0+57.1s to t0+117.1s : R > 15.3

The second image is 30.0s exposure in tracking mode:
t0+132.5s to t0+162.5s : R > 15.7

We co-added a series of exposures:
t0+132.5s to t0+426.0s : R > 17.2

Magnitudes were estimated with the nearby USNO-B1 stars
and are not corrected for galactic dust extinction.


GRB_name: GRB160417A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19384
SUBJECT: GRB 160417A, the review of the sky area in plate archive
DATE:    16/05/04 20:55:29 GMT
FROM:    Valentyna Golovnya at Main Astro Obs,Kyiv  <golov_v@ukr.net>

V. V. Golovnia (Main Astro Obs., Kyiv)
report:
We have undertaken the review of the sky area of GRB 160417A (J.P. Osborne
et al. GCN Circ. 19318) on astronegatives, collected in Ukrainian plate
archive (1976-1996). All the plates with the possible object appearance are
digitized using Epson Expression 10000XL flatbed scanner and the images
have been placed into Golosiiv Plate Archive database DBGPA with open
access to them. The list of plates is given in the table:

yyyymmdd/TstartUT- ---Plates--- -Exp. Mag --USNO-A2--
19930202/21:16:48 GUA040C002102 18.9 14.8 0975-05657018
19930216/20:33:08 GUA040C002131 19.5 16.0 0975-05654878
19930312/18:39:20 GUA040C002146 22.5 15.3 0975-05651231

Plates -the plates archive identifier of DWA D/F=400/2000, M=103"/mm
(Marsden's number - 083) the plate number [1].
Exp. - Duration of the maximum exposures (minutes).
Mag - Limited Bmag, derived in the 9 minutes area around the location
given in J.P. Osborne et al.(GCN Circ. 19318):
RA(J2000): 08h 01m 01.64s, Dec(J2000): +07d 39' 46.1".
USNO-A2 - Comparison star.
The preview images of 3 areas together with the 9 min. of arc area
from Aladin can be found in
http://gua.db.ukr-vo.org/img/grb/160417A/index.html.
The images with full resolution are available via e-mail on demand.

References:
1.L.Pakuliak DATABASE of GOLOSIIV PLATE ARCHIVE (DBGPA V2.0),
http://gua.db.ukr-vo.org.
 
 


GRB_name: GRB160504A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19385
SUBJECT: GRB 160504A: NOT upper limits
DATE:    16/05/04 22:22:05 GMT
FROM:    Thomas Kruehler at MPE Garching  <kruehler@mpe.mpg.de>

T. Kruehler (MPE Garching), A. de Ugarte Postigo (IAA-CSIC and
DARK/NBI), and T. Kuutma (NOT) report on behalf of a larger
collaboration:

We observed the field of GRB 160504A (Malesani et al., GCN #19382)
with the NOT equipped with ALFOSC. Imaging in the r, i and z-band
filter started at 20:54:10 UT on 2016-05-04, 1.4 hr after the GRB
trigger.

We detect no sources in the enhanced XRT error circle given at
http://www.swift.ac.uk/sper/685124/.

Calibrating our images against magnitudes from field stars of the
SDSS catalog, we measure preliminary upper limits of

r > 23.3 mag
i > 22.8 mag
z > 22.0 mag

These limits are not corrected for the expected foreground
extinction corresponding to a reddening of E(B-V) = 0.01 mag
(Schlafly & Finkbeiner 2011).


GRB_name: GRB160504A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19386
SUBJECT: GRB 160504A: Enhanced Swift-XRT position
DATE:    16/05/04 22:27:27 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 559 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 160504A, 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 = 170.07224, +56.00158 which is equivalent
to:

RA (J2000): 11h 20m 17.34s
Dec (J2000): +56d 00' 05.7"

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: GRB160504A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19387
SUBJECT: GRB 160504A: Swift-XRT refined Analysis
DATE:    16/05/05 03:23:39 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. Malesani report on behalf of the Swift-XRT team:

We have analysed 7.8 ks of XRT data for GRB 160504A (Malesani et al.
GCN Circ. 19382), from 80 s to 18.1 ks after the  BAT trigger. The data
comprise 31 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. 19386).

The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=2.4 (+1.2, -3.4). At T+100 s  the decay
steepens to an alpha of 5.5 (+0.9, -0.7). The light curve breaks again
at T+209 s to a decay with alpha=0.15 (+0.08, -0.65),  before a final
break at T+4742 s s after which the decay index is 0.68 (+0.15, -0.14).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.97 (+/-0.15). The
best-fitting absorption column is  1.1 (+/-0.4) x 10^21 cm^-2, in
excess of the Galactic value of 8.1 x 10^19 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 3.4 x 10^-11 (4.2 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      1.1 (+/-0.4) x 10^21 cm^-2
Galactic foreground: 8.1 x 10^19 cm^-2
Excess significance: 4.4 sigma
Photon index:      1.97 (+/-0.15)

If the light curve continues to decay with a power-law decay index of
0.68, the count rate at T+24 hours will be 0.022 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.5 x
10^-13 (9.3 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/00685124.

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


GRB_name: GRB160504A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19388
SUBJECT: GRB 160504A: Bassano Bresciano Observatory upper limits
DATE:    16/05/05 07:52:39 GMT
FROM:    Ulisse Quadri at Bassano Bresciano Obs  <oabb@ulisse.bs.it>

U.Quadri, L.Strabla and R.Girelli report:

We imaged the field of GRB 160504A detected by SWIFT(trigger 685124)
with the robotic telescope of (IAU station 565) Bassano Bresciano 
Observatory, Italy. Member of: 
AAVSO - American Association of Variable Star Observers.
ISSP - Italian Supernovae Search Project.
UAI/SSV - Unione Astrofili Italiani/sezione stelle variabili.

The observations started 22.45 min after the GRB trigger,  
with our Schmidt telescope D=320/400 mm F/D=3.1.

Weather conditions were good.

We co-added 2 series of 20 exposures of 120 sec each.

Start T0+      End T0+      Vlim
22.45 min    111.33 min     20

We did not found any optical counterpart in the error 
box of the XRTcandidate.
(D. Malesani (DARK/NBI), J. A. Kennea (PSU)et al)

Magnitudes were estimated with the UCAC4 cat. and 
are not corrected for galactic dust extinction.

Reference:
http://www.osservatoriobassano.org/GRB.asp

The message may be cited.


GRB_name: GRB160504A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  19389
SUBJECT: GRB160504A: Gemini NIR Observations
DATE:    16/05/05 15:38:40 GMT
FROM:    S. Bradley Cenko at NASA/GSFC  <brad.cenko@nasa.gov>

S. B. Cenko (NASA/GSFC), A. J. Levan (U. Warwick), N. R. Tanvir (U. Leicester), A. Cucchiara (STScI), and A. Fruchter (STScI) report on behalf of a larger collaboration:

We imaged the location of GRB160504A (Malesani et al., GCN 19382) with the Near Infrared Imager and Spectrometer (NIRI) on the 8 m Gemini North telescope beginning at 5:24 UT on 5 May 2016 (~ 9.9 hr after the Swift trigger).  A total of 10 min of integration was obtained in each of the J, H, and K filters.  Within the enhanced XRT localization (Goad et al., GCN 19386) we identify a single faint source at J2000 coordinates:

  RA: 11:20:17.18
  Dec: +56:00:04.7

Using a nearby point source from 2MASS for calibration, we calculate the following AB magnitudes for this object:

J = 23.6 +/- 0.4
H = 23.8 +/- 0.4
K = 23.3 +/- 0.2

Given the faintness of the object, we cannot determine at this time if it associated with GRB160504A.


