The Search for Gamma-ray Emission from Fermi-GBM and Swift-BAT in Coincidence with GWTC Events

Since the detection of the binary neutron star merger (GW170817) in coincidence with the short gamma ray burst (GRB 170817A), the search for electromagnetic emission from similar events has been an imperative part of multi-messenger astronomy. Therefore, we searched Fermi Gamma-ray Burst Monitor (Fermi-GBM) and Swift Burst Alert Telescope (Swift-BAT) rate data around the GW event times presented by the LIGO/Virgo/Kagra Collaboration (LVK) in the GWTC Catalog, the most sensitive gravitational wave search to date. Using Fermi-GBM on-board triggers and two sub-threshold searches, the Targeted and the Untargeted Search, as well as rate data from Swift-BAT, we determine whether there are any coincident gamma-ray transients associated with the GWTC events. We present updates to the Fermi-GBM Targeted search to enhance its sensitivity for identifying short gamma-ray bursts (GRBs) below the triggering threshold of Fermi-GBM. To date, no new joint events beyond GRB 170817A and GW170817 have been found. Using both the Fermi-GBM Targeted Search and the Swift-BAT search, we place upper limits on the associated gamma-ray luminosity for the GWTC events and present joint upper limit skymaps. Using the lack of electromagnetic emission from the binary black hole mergers presented in GWTC, we strive to constrain theoretical models of how such emission is produced.