The Search for the Electromagnetic Counterpart of Gravitational Wave Events with VERITAS

The detection of gamma rays originating from the 2017 gravitational wave (GW) event GW170817 energized the field of multimessenger astronomy. This event showed that binary neutron stars are promising contenders for producing gamma-ray bursts (GRBs), raising questions about the possible presence of a very high-energy (VHE) gamma-ray counterpart. The Very Energetic Radiation Imaging Telescope Array System (VERITAS) is a ground-based gamma-ray instrument located in southern Arizona, USA, comprising of four 12m optical reflectors detecting gamma rays in the 100 GeV - 30 TeV energy range. VERITAS is searching for the potential existence of the VHE gamma-ray component of GW events. To find these electromagnetic signals, VERITAS takes observations in spatial coincidence with GW detections from the Laser Interferometer Gravitational-Wave Observatory (LIGO) shortly after the event is identified, which has been the case for LIGO O3 (third observing run) and all of O4 so far. VERITAS has followed up on 12 GW events in LIGO O3 and 12 in LIGO O4 to date, with the majority of all events having >95% probability confidence of being binary black hole mergers. I will discuss more information about the events mentioned and details about VERITAS's analysis of these compact binary mergers. The detection of VHE photons from GW events could uncover information about the environment of these events and the emission mechanism producing VHE photons.