Using gravitational wave early warning to pre-point neutron star mergers with Imaging Atmospheric Cherenkov telescopes

TL;DR

This paper explores the potential of using gravitational wave early warnings to pre-point Imaging Atmospheric Cherenkov telescopes at neutron star mergers, enabling the detection of prompt TeV gamma-ray emission.

Contribution

It proposes a novel observational strategy combining GW early warnings with IACTs to capture high-energy signals before neutron star mergers.

Findings

Early warning alerts could arrive tens of seconds before mergers.

Pre-pointing telescopes could detect prompt TeV emission.

Technical challenges include reducing latency and improving GW-telescope coordination.

Abstract

The LIGO-Virgo-KAGRA (LVK) collaboration has recently made it possible for early warning alerts to be sent out, potentially before the end of the gravitational wave (GW) emission from a neutron star binary. If we get such alerts in this (the fourth) or the next observing run they may arrive up to tens of seconds before the merger, which is comparable to the slewing times of the Large Size Telescopes (designed to observe very high energy gamma rays): it would be therefore possible to point to the source right before it starts emitting an electromagnetic signal. This new mode of observation would allow us to detect the TeV component of prompt emission, which is currently poorly constrained and understood. There are many technical challenges to overcome before this can be realized: improving the synergy between gravitational observatories and telescopes, reducing operational latencies and, from the gravitational wave side, providing more information, such as real-time updates on early warning candidates and the probability distribution of the inclination angle. Although we may need to wait a few years -- in the worst case scenario, until the next generation of GW detectors is built -- before the first detection of this kind is made, implementing these improvements is a necessity.