Analyzing GW231109_235456 and understanding its potential implications for population studies, nuclear physics, and multi-messenger astronomy

TL;DR

This paper analyzes the sub-threshold gravitational-wave event GW231109_235456, exploring its implications for neutron star properties, population models, and multi-messenger astronomy, and forecasts future constraints with next-generation detectors.

Contribution

It provides the first detailed analysis of GW231109_235456, supporting neutron star mass distribution models and constraining the equation of state using current and future detectors.

Findings

Supports double Gaussian neutron star mass distribution

Suggests prompt black hole formation from the merger

Future detectors can measure neutron star radius within 300-400 meters

Abstract

We study the gravitational-wave trigger GW231109_235456, a sub-threshold binary neutron star merger candidate observed in the first part of the fourth observing run of the LIGO-Virgo-KAGRA collaboration. Assuming the trigger is of astrophysical origin, we analyze it using state-of-the-art waveform models and investigate the robustness of the inferred source parameters under different prior choices in Bayesian inference. We assess the implications for population studies, nuclear physics, and multi-messenger astronomy. Analysing the component masses, we find that GW231109_235456 supports the proposed double Gaussian mass distribution of neutron star masses. Moreover, we find that the remnant most likely collapsed promptly to a black hole and that, because of the large distance, a possible kilonova connected to the merger was noticeably dimmer than AT2017gfo. In addition, we provide constraints on the equation of state from GW231109_235456 alone, as well as combined with GW170817 and GW190425. In our projections for the future, we simulate a similar event using the upcoming generation of gravitational-wave detectors. Our findings indicate that we can constrain the neutron star radius with an accuracy of 400 meters using the Einstein Telescope alone, or 300 meters when combined with the Cosmic Explorer, both at 90% credibility.