Gamma-ray flares from blazars can be accompanied by high-energy neutrino emission. To better understand this phenomenon, an international research team has statistically analyzed 145 bright blazars. They constructed weekly binned light curves and utilized a Bayesian algorithm, finding that their sample was dominated by blazars with low flare duty cycles and energy fractions. The study suggests that high-energy neutrinos of blazars might be produced mainly during the flare phase.
Blazars belong to the family of active galactic nuclei called quasars. What differentiates them from quasars is that the flares ejected out of these active galactic nuclei are pointed toward the Earth. These flares contain high-energy cosmic rays which are released from the core of these galaxies as jets spanning many light years. Such cosmic rays can interact with photons to produce subatomic particles called neutrinos.
Gamma-ray flares from blazars are thought to be the primary events behind neutrino detection in the sky. In 2017, the South Pole neutrino detector “IceCube” detected a high-energy neutrino event whose timings and positioning in the night sky coincided with the flare of a blazar called TXS 0506+056. Some scientists suggest that there could be a population of blazars whose flares are accompanied by high-energy neutrino emission. However, the relationship between blazar flaring activity and neutrino flux is yet to be properly understood.
In this regard, an international research team, led by Professor Kenji Yoshida from the Department of Electronic Information Systems at Shibaura Institute of Technology, Japan, has recently performed a comprehensive statistical analysis to understand the contribution of gamma-ray flares to neutrino emission. The team included Maria Petropoulou from the National and Kapodistrian University of Athens, Kohta Murase from The Pennsylvania State University, and Foteini Oikonomou from the Norwegian University of Science and Technology. Their paper…