GW190425: Pan-STARRS and ATLAS coverage of the skymap and limits on optical emission associated with FRB190425

TL;DR

This study reports on optical follow-up observations of GW190425, a binary neutron star merger, and investigates the potential association with FRB 190425, setting limits on kilonova emission and discussing implications for the FRB-GW connection.

Contribution

The paper provides the first optical coverage of GW190425's skymap shortly after detection and assesses the possible link between the GW event and FRB 190425, constraining kilonova models.

Findings

No optical emission detected from the GW190425 localization

Optical limits rule out magnetar-enhanced kilonova emission

Disfavors, but does not disprove, the FRB-GW association hypothesis

Abstract

GW190425 is the second of only two binary neutron star (BNS) merger events to be significantly detected by the LIGO-Virgo- Kagra gravitational wave detectors. With a detection only in LIGO Livingston, the skymap containing the source was large and no plausible electromagnetic counterpart was found in real time searching in 2019. Here we summarise our ATLAS and Pan-STARRS wide-field optical coverage of the skymap beginning within 1 hour and 3 hours respectively of the GW190425 merger time. More recently, a potential coincidence between GW190425 and a fast radio burst FRB 190425 has been suggested, given their spatial and temporal coincidence. The smaller sky localisation area of FRB 190425 and its dispersion measure have led to the identification of a likely host galaxy, UGC 10667 at a distance of 141 +/- 10 Mpc. Our optical imaging covered the galaxy 6.0 hrs after GW190425 was detected and 3.5 hrs after the FRB 190425. No optical emission was detected and further imaging at +1.2 and +13.2 days also revealed no emission. If the FRB 190425 and GW190425 association were real, we highlight our limits on kilonova emission from a BNS merger in UGC 10667. The model for producing FRB 190425 from a BNS merger involves a supramassive magnetised neutron star spinning down by dipole emission on the timescale of hours. We show that magnetar enhanced kilonova emission is ruled out by optical upper limits. The lack of detected optical emission from a kilonova in UGC 10667 disfavours, but does not disprove, the FRB-GW link for this source.