Speaker
Description
Since the joint detection of gravitational waves from GW 170817 and electromagnetic radiation from a short gamma-ray burst, GRB 170817A, the multimessenger community has worked extensively to investigate these events. This detection showed that binary neutron star mergers are progenitors of short GRBs and demonstrated the advantages of multimessenger observations. Although GRB 170817A was observed across the electromagnetic spectrum, it was not detected in the very-high-energy (VHE; >100 GeV) energy range. This raises the question of whether a VHE counterpart to these mergers exists, as well as the possibility of electromagnetic emission from other GW events such as binary black hole (BBH) mergers. The Very Energetic Radiation Imaging Telescope Array System (VERITAS), a ground-based telescope in southern Arizona, is sensitive to VHE gamma rays and is capable of rapid follow-up observations of GW alerts. Here, we perform a population-level search for VHE gamma rays from BBH mergers reported in the LIGO-Virgo-KAGRA (LVK) Gravitational-Wave Transient Catalog and studied with VERITAS. We use 3D localization maps from LVK to account for the 90% credible regions, distance posteriors, and VERITAS sky coverage for each event. With this information, we calculate the gravitational-wave energy emitted in each event and place upper limits on the isotropic-equivalent gamma-ray energy to constrain the fraction of merger energy that must be emitted in VHE gamma rays for detection. We produce a probability detection curve to determine the fraction of merger energy that would need to be emitted in VHE gamma rays for VERITAS to have a 95% or greater probability of detecting at least one event in our list of GW events. Constraining the amount of VHE emission can provide insight into the environment of BBH mergers and the possible emission mechanisms that produce VHE particles in these extreme events. This framework provides a foundation for future GW-triggered VHE searches.
