Black Hole/Pulsar Binaries in the Galaxy

TL;DR

This study models the formation and observable properties of black hole/neutron star binaries in the Milky Way, estimating their numbers and detection prospects with future radio telescopes.

Contribution

It introduces updated population synthesis models for BH/NS binaries, accounting for uncertainties and predicting their observable characteristics and detection rates.

Findings

Estimated 3-80 BH/pulsar binaries in the Galaxy.

Around 10% of these binaries could be detected by FAST.

The birthrate of BH/NS binaries is between 0.6 and 13 per million years.

Abstract

We have performed population synthesis calculation on the formation of binaries containing a black hole (BH) and a neutron star (NS) in the Galactic disk. Some of important input parameters, especially for the treatment of common envelope evolution, are updated in the calculation. We have discussed the uncertainties from the star formation rate of the Galaxy and the velocity distribution of NS kicks on the birthrate ($ \sim 0.6-13 \rm\, Myr^{-1}$) of BH/NS binaries. From incident BH/NS binaries, by modelling the orbital evolution duo to gravitational wave radiation and the NS evolution as radio pulsars, we obtain the distributions of the observable parameters such as the orbital period, eccentricity and pulse period of the BH/pulsar binaries. We estimate that there may be $\sim 3-80 $ BH/pulsar binaries in the Galactic disk and around 10\% of them could be detected by the Five-hundred-meter Aperture Spherical radio Telescope.