Predicting electromagnetic counterparts using low-latency, gravitational-wave data products

TL;DR

This paper develops a method to predict electromagnetic counterparts of gravitational-wave events using low-latency data, aiming to improve follow-up observations by estimating ejecta properties and lightcurve contours.

Contribution

It extends existing classifiers to predict ejecta characteristics and lightcurves, enhancing the ability to identify electromagnetic counterparts in real-time.

Findings

Method tested on real LIGO-Virgo events

Uncertainty mainly due to ejecta composition and binary parameter constraints

Potential to improve electromagnetic follow-up strategies

Abstract

Searches for gravitational-wave counterparts have been going in earnest since GW170817 and the discovery of AT2017gfo. Since then, the lack of detection of other optical counterparts connected to binary neutron star or black hole - neutron star candidates has highlighted the need for a better discrimination criterion to support this effort. At the moment, the low-latency gravitational-wave alerts contain preliminary information about the binary properties and, hence, on whether a detected binary might have an electromagnetic counterpart. The current alert method is a classifier that estimates the probability that there is a debris disc outside the black hole created during the merger as well as the probability of a signal being a binary neutron star, a black hole - neutron star, a binary black hole or of terrestrial origin. In this work, we expand upon this approach to predict both the ejecta properties and provide contours of potential lightcurves for these events in order to improve follow-up observation strategy. The various sources of uncertainty are discussed, and we conclude that our ignorance about the ejecta composition and the insufficient constraint of the binary parameters, by the low-latency pipelines, represent the main limitations. To validate the method, we test our approach on real events from the second and third Advanced LIGO-Virgo observing runs.