Parameter Estimation on LIGO-Virgo-KAGRA O4a Binary Merger Triggers with Sub-solar Mass Components

Abstract

The LIGO-Virgo-KAGRA collaboration has reported the results for searches for sub-solar mass components in compact binary coalescence during observing run O4a. No detection candidates were identified, but the most significant seven triggers were reported. We present the results of Bayesian parameter inference on these triggers. Five of the triggers show agreement between the Bayesian parameter estimation and the search pipeline trigger. Our results show that three of the triggers may contain a possible sub-solar mass component. Parameter estimation indicates that the other two events, if real, would be neutron star - black hole binaries. The remaining two triggers do not provide informative parameter estimation. We also study three O4a compact binary coalescence triggers, and one O3 trigger, that have been noted by three other groups, and our parameter estimation indicates that three of these may contain a sub-solar mass component. We study the data quality associated with these triggers. Finally, we discuss the challenges for parameter estimation on compact binary coalescence events containing a sub-solar mass component: long signal duration, possible small chirp masses, possible small mass ratios, and data quality issues over potentially hundreds of seconds of data.