Multi-messenger study of GRBs and their remnants

The era of gravitational-wave (GW) multi-messenger astronomy began with the discovery of GWs from the binary neutron star merger GW170817, its associated (short) gamma-ray burst (GRB), and broad-band afterglow. Through multi-messenger astronomy, we can probe the nature of GRB remnants (black holes, BHs, versus neutron stars, NSs), and how the remnant properties map into the properties of the afterglows and of the binary progenitors. An effective strategy for multimessenger discovery is a two-fold one that uses electromagnetic (EM) triggers of GRBs to carry out GW archival searches, and GW triggers of coalescing binary systems to search for their EM afterglows. In this context, this work presents an analysis of all GRBs detected by Swift during initial LIGO 6th Science run (S6), advanced LIGO first and second observing runs (O1, O2), and the first half of advanced LIGO third observing run (O3). The goal of this analysis is to identify GRBs with X-ray afterglow features suggestive of long-lived, highly-magnetized NS remnants. These GRBs could represent promising targets for archival GW searches with LIGO. For the first half of the on-going LIGO O3 run, this work also presents results of a realtime search for radio afterglows of GW triggers, carried out within the Jansky VLA mapping of Gravitational Wave bursts as Afterglows in Radio (JAGWAR) collaboration. Specifically, we present initial results for the GW event candidates dubbed S190814bv and S191216ap, which were initially classified as likely NS-NS/NS-BH mergers. We show the sensitivity level of these searches, and discuss them in the context of future searches for GW-triggered radio afterglows with the Jansky VLA.