P13 an ULX that is a potential progenitor of merging BH-NS system

TL;DR

This study models the future evolution of ULX P13, suggesting it could become a BH-NS system that merges within the universe's age, contributing to gravitational wave sources detectable by LIGO/Virgo.

Contribution

It provides the first detailed evolutionary pathway from a specific ULX to a potential BH-NS merger, estimating detection rates for gravitational wave observatories.

Findings

Approximately 70% chance of the system surviving supernova

One-third of BH-NS systems merge within Hubble time

Estimated detection rate of 0.1 per year for LIGO/Virgo

Abstract

We have studied the future evolution of a recently discovered ULX source P13 in NGC7793. This source was shown to contain a 5-15$M_{\odot}$ black hole and a massive 18-23$M_{\odot}$ B9Ia companion on a 64 day orbit. For low black hole mass (5-10$M_{\odot}$) and high companion mass $\gtrsim 20 M_{\odot}$ the binary is predicted to initiate a common envelope evolution in near future and significantly decrease the orbital separation (6 hr orbit). This leads to a high probability ($\sim70\%$) of the system surviving a supernova explosion that will form a neutron star out of the companion. About one third of the surviving BH-NS systems will merge within Hubble time and be a source of high frequency gravitational radiation. We estimate that the chances of detection of BH-NS systems with advanced LIGO/Virgo that form via P13-evolutionary channel are at the level of 0.1 yr$^{-1}$ with wide range of allowed probability $0 \div 0.6$yr$^{-1}$. This is the fourth empirical estimate of BH-NS merger rate.