Search for high energy [formula omitted]-rays from the direction of the candidate electromagnetic counterpart to the binary black hole merger gravitational-wave event S190521g

Abstract

The gravitational-wave event S190521g — a likely binary black hole merger in the accretion disk of an active galactic nucleus — was accompanied by an optical counterpart. Such dense environments around luminous energy release regions are favorable for high energy γ-ray production. We report on a search for high energy γ-rays from the direction of the candidate electromagnetic counterpart to the S190521g event using publicly-available data of the Fermi-LAT space γ-ray telescope. No significant signal was found. We present upper limits on the spectral energy distribution of the source in the 100 MeV–300 GeV energy range. We discuss the importance of studying S190521g-like transients in the context of cosmic ray acceleration, γ-ray and neutrino production in such sources.