Coincident detection significance in multimessenger astronomy

TL;DR

This paper develops a Bayesian method to determine if signals in different datasets originate from the same source, with application to multimessenger astronomy, exemplified by the GW170817 and GRB 170817A coincidence.

Contribution

It introduces a Bayesian criterion incorporating posterior overlaps to assess common source origin in multimessenger signals, advancing analysis techniques in astrophysics.

Findings

The method strongly favors the common source hypothesis for GW170817 and GRB 170817A.

The Bayesian criterion effectively integrates spatial and temporal data.

Application demonstrates improved confidence in multimessenger source association.

Abstract

We derive a Bayesian criterion for assessing whether signals observed in two separate data sets originate from a common source. The Bayes factor for a common vs. unrelated origin of signals includes an overlap integral of the posterior distributions over the common source parameters. Focusing on multimessenger gravitational-wave astronomy, we apply the method to the spatial and temporal association of independent gravitational-wave and electromagnetic (or neutrino) observations. As an example, we consider the coincidence between the recently discovered gravitational-wave signal GW170817 from a binary neutron star merger and the gamma-ray burst GRB 170817A: we find that the common source model is enormously favored over a model describing them as unrelated signals.