Swift X-ray Follow-Up Observations of Gravitational Wave and High-Energy Neutrino Coincident Signals

TL;DR

This paper reports on Swift Observatory's prompt X-ray follow-up observations of joint gravitational wave and high-energy neutrino events during LIGO/Virgo's third run, improving search techniques despite no detections.

Contribution

It introduces enhanced tiling techniques for joint GW and neutrino error regions and demonstrates the system's readiness for future multi-messenger discoveries.

Findings

No X-ray counterparts detected in the observed events.

Follow-up procedures improved tiling coverage of error regions.

System is prepared for future multi-messenger alerts.

Abstract

Electromagnetic observations of gravitational wave and high-energy neutrino events are crucial in understanding the physics of their astrophysical sources. X-ray counterparts are especially useful in studying the physics of the jet, the energy of the outflow, and the particle acceleration mechanisms in the system. We present the Neil Gehrels Swift Observatory prompt searches for X-ray counterparts to the joint gravitational wave and high-energy neutrino coincident events that happened during the third observing run of LIGO/Virgo. Swift observed the overlap between gravitational wave and neutrino error regions for three of the considerable (p-value < 1%) joint gravitational wave and high-energy neutrino coincident alerts, which were generated by the IceCube Neutrino Observatory in realtime after triggering by the LIGO/Virgo gravitational wave public alerts. The searches did not associate any X-ray counterparts to any of the joint gravitational wave and high-energy neutrino coincident events, however, the follow-up of these alerts significantly improved the tiling techniques covering regions between the gravitational wave sky maps and neutrino's error regions, making the realtime system ready for the future potential discoveries. We will discuss the details of each follow-up procedure, the results of each search, and the plans for future searches.