Catching the next wave: gamma-ray counterparts to gravitational waves
Corinne Fletcher, Joshua Wood, Rachel Hamburg, Peter Veres et al. on behalf of the Fermi-GBM Team
Milena Crnogorčević, James DeLaunay, Aaron Tohuvavohu, et al. for Swift-BAT
and the LIGO/Virgo/ KAGRA Collaboration
The detection of gravitational waves (GWs) from a merger of two neutron stars (GW170817) and their short gamma-ray burst counterpart (GRB 170817A) introduced new ways to explore a number of long-standing questions in astronomy (e.g., the origins of heavy elements or the nature of the environments of particle acceleration in the Universe.) No other counterpart detection to a gravitational wave event has been confirmed to date. We present an offline, follow-up search for excess emission of gamma-rays with the Fermi Gamma-ray Burst Monitor (Fermi-GBM) and Swift- Burst Alert Telescope (Swift--BAT), in spatial and temporal correspondence to gravitational-wave events reported by the LIGO/Virgo/Kagra (LVK) Collaboration in their third observing run (O3). We utilize Fermi--GBM on-board triggers and sub-threshold searches in combination with Swift--BAT rate data to look for any gamma-ray excess associated with GW events detected in O3. We report no new joint detections to date; however, we place flux upper-limits, allowing us to explore constraints on the current theoretical models describing the production of gamma-rays in these environments.
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Cross-correlating unresolved gamma rays with neutrinos
Michela Negro, Milena Crnogorčević, Eric Burns, Eric Charles, Lea Marcotulli, Regina Caputo
With the recent coincident detections of electromagnetic radiation and gravitational waves (GW 170817) or neutrinos (TXS 0506+056), the new era of multimessenger astrophysics has begun. Particularly interesting are the searches for spatial coincidence between the high-energy astrophysical neutrinos detected by the IceCube (IC) Observatory and gamma-ray photons detected by Fermi. So far, only sources resolved with the Fermi’s Large Area Telescope (LAT) have been considered in correlation with IC neutrinos; in turn neglecting any emission from sources too faint to be resolved by the current gamma-ray instruments. Here, we present the first consideration of such unresolved emission, both using simulations and real observations. Although we report no significant correlation in the current all-sky neutrino and gamma-ray observed maps, we compute upper limits on the fraction of the observed neutrinos that must be astrophysical for a significant coincident detection. Furthermore, our analysis provides an excellent scientific motivation for the next generation of neutrino and gamma-ray instruments to shed light on physical processes responsible for production of these events.
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