Binary population synthesis with probabilistic remnant mass and kick prescriptions

TL;DR

This paper explores how probabilistic models for remnant masses and kicks affect binary star evolution, revealing implications for observed neutron star and black hole populations, including the mass gap and extreme systems.

Contribution

It introduces a probabilistic prescription for remnant masses and kicks in binary population synthesis, impacting the predicted distributions of compact object systems.

Findings

Populates the neutron star-black hole mass gap with low-mass black holes.

Reduces predicted low-mass black hole X-ray binaries, aligning with observations.

Supports formation of heavy binary neutron stars like GW190425, but overestimates Galactic double neutron star masses.

Abstract

We report on the impact of a probabilistic prescription for compact remnant masses and kicks on massive binary population synthesis. We find that this prescription populates the putative mass gap between neutron stars and black holes with low-mass black holes. However, evolutionary effects reduce the number of X-ray binary candidates with low-mass black holes, consistent with the dearth of such systems in the observed sample. We further find that this prescription is consistent with the formation of heavier binary neutron stars such as GW190425, but over-predicts the masses of Galactic double neutron stars. The revised natal kicks, particularly increased ultra-stripped supernova kicks, do not directly explain the observed Galactic double neutron star orbital period--eccentricity distribution. Finally, this prescription allows for the formation of systems similar to the recently discovered extreme mass ratio binary GW190814, but only if we allow for the survival of binaries in which the common envelope is initiated by a donor crossing the Hertzsprung gap, contrary to our standard model.