Galaxy-Targeting Approach Optimized for Finding the Radio Afterglows of Gravitational Wave Sources

Abstract

Kilonovae and radio afterglows of neutron star merger events have been identified as the two most promising counterparts, of these gravitational wave sources, that can provide arcsecond localization. While several new and existing optical search facilities have been dedicated to finding kilonovae, factors such as dust obscuration and the daytime sky may thwart these searches in a significant fraction of gavitational wave events. Radio-only searches, being almost immune to these factors, are equally capable of finding the counterparts and in fact offer a complementary discovery approach, despite the modest fields of view for many of the present-day radio interferometers. Such interferometers will be able to carry out competitive searches for the electromagnetic counterparts through the galaxy targeting approach. Adapting and improving on an existing algorithm by Rana et al. 2017. we present here a method that optimizes the placement of radio antenna pointings, integration time, and antenna slew. We simulate 3D gravitational wave localizations to find the efficacy of our algorithm; with substantial improvements in slew overhead and containment probability coverage, our algorithm performs significantly better than simple galaxy-rank-ordered observations. We propose that telescopes such as the Very Large Array, MeerKAT, Australia Telescope Compact Array and the Gaint Meterwave Radio Telescope, having fields of view ≲1 deg² and searching for the counterparts of nearby GW events over tens of square degrees or larger, will especially benefit from this optimized galaxy-targeting approach for electromagnetic counterpart searches.

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