High-energy electromagnetic offline follow-up of LIGO-Virgo gravitational-wave binary coalescence candidate events

TL;DR

This paper develops and demonstrates two methods for detecting electromagnetic counterparts to gravitational-wave events using archival high-energy data from NASA instruments, improving the ability to identify true GW signals.

Contribution

It introduces two custom pipelines for joint GW and electromagnetic data analysis, enhancing detection efficiency and background rejection for GW candidate events.

Findings

Reduced GW background noise by 15-20% using electromagnetic coincidence

Demonstrated effective detection of weak gamma-ray burst counterparts

Validated methods with simulated GW background events

Abstract

We present two different search methods for electromagnetic counterparts to gravitational-wave (GW) events from ground-based detectors using archival NASA high-energy data from the Fermi-GBM and RXTE-ASM instruments. To demonstrate the methods, we use a limited number of representative GW background noise events produced by a search for binary neutron star coalescence over the last two months of the LIGO-Virgo S6/VSR3 joint science run. Time and sky location provided by the GW data trigger a targeted search in the high-energy photon data. We use two custom pipelines: one to search for prompt gamma-ray counterparts in GBM, and the other to search for a variety of X-ray afterglow model signals in ASM. We measure the efficiency of the joint pipelines to weak gamma-ray burst counterparts, and a family of model X-ray afterglows. By requiring a detectable signal in either electromagnetic instrument coincident with a GW event, we are able to reject a large majority of GW candidates. This reduces the signal-to-noise of the loudest surviving GW background event by around 15-20%.