Search for Gamma-Ray Burst Associations with Gravitational-wave Candidates

Motivated by the confirmed multimessenger event GW170817/GRB 170817A, we carry out an archival search for temporal and spatial associations between gamma-ray bursts (GRBs) and both significant and subthreshold gravitational wave (GW) candidates reported in the public search products of GWTC-2.1, GWTC-3, and GWTC-4.0. GRB trigger times and sky positions are taken from the GRBweb compilation of Swift-BAT and Fermi-GBM. GW candidates from the search pipelines are correlated with GRBs using time windows from 1 s to 10³ s and spatial consistency tests based on the released sky-localization maps. We find no statistically significant GW–GRB associations on short timescales comparable to that of GW170817/GRB 170817A. The closest temporal connection is found between GRB 231126A and the GW candidate 231126_010928, with a delay of Δt = 164.692 s, and with the GRB localization overlapping a high-probability region of the GW skymap. From the associated three-dimensional BAYESTAR localization, we infer a luminosity distance of (Formula presented) DL=3951−1970+2497  Mpc (90% credible interval). For this candidate, we additionally performed Bayesian parameter estimation using Bilby with Markov Chain Monte Carlo sampling to obtain posterior parameters.