The sources of the high-energy astrophysical neutrinos detected by the IceCube Neutrino Observatory remain largely unknown. A promising candidate is a tidal disruption event (TDE), which occurs when a star is ripped apart by the strong gravitational field of a supermassive black hole. Interest in TDEs and other transients as potential sources grew after a paper authored by external astronomers pointed out that several high-energy IceCube neutrinos were in both spatial and temporal coincidence with TDEs.
Interestingly, these candidate neutrino-associated transients also exhibited strong infrared emission. This can occur when dust surrounding the central black hole absorbs radiation from the TDE and re-emits it at longer wavelengths, producing an infrared “dust echo.”
In a paper submitted to Astronomy & Astrophysics, the IceCube Collaboration presents results of a search for high-energy neutrino emission from a population of infrared-bright transients. A statistically significant excess of neutrinos was not found and limits were placed on the population’s contribution to the astrophysical neutrino flux observed by IceCube.
“Infrared dust echoes provide a complementary way of tracing transient activity around supermassive black holes, including events that may be obscured at optical wavelengths,” explains Teresa Pernice, a PhD student at Deutsches Elektronen-Synchrotron in Germany who led the study.
The collaborators performed a stacking analysis that allowed them to search for a weak neutrino signal shared across the population that might be too faint to detect from any individual source. The analysis used 10 years of IceCube data and a sample of 393 infrared accretion flares (sudden bursts of infrared light caused by material falling toward a black hole) to look for a cumulative high-energy neutrino signal. In addition to the stacking search, the collaborators tested different possible neutrino energy spectra to constrain the contribution to the astrophysical neutrino flux.
For future studies, Pernice notes upcoming surveys, such as by the Vera C. Rubin Observatory, that “will discover larger numbers of new transients, including thousands of TDE candidates per year.” Combining these observations with data from more sensitive neutrino detectors, like the proposed IceCube-Gen2, will allow researchers to test a wider range of source populations, bringing them closer to identifying sources of high-energy neutrinos.
+ info “Search for High-Energy Neutrinos from Infrared Flares,” IceCube Collaboration: R. Abbasi et al. Submitted to Astronomy & Astrophysics. arXiv