Detecting Black Hole Binaries by Gaia

TL;DR

This paper assesses Gaia's potential to detect black hole binaries through companion star orbital motion, estimating 200-1000 detections over five years, and highlights how these observations can constrain black hole mass relations.

Contribution

It provides the first detailed estimates of Gaia's capability to detect black hole binaries and explores how these detections can inform models of black hole formation.

Findings

Gaia can detect approximately 200-1000 black hole binaries within 5 years.

The distribution of black hole masses detected by Gaia is sensitive to the stellar-to-black hole mass relation.

Black hole detections by Gaia can help constrain models of stellar evolution and black hole formation.

Abstract

We study the prospect of the Gaia satellite to identify black hole binary systems by detecting the orbital motion of the companion stars. Taking into account the initial mass function, mass transfer, common envelope phase, interstellar absorption and identifiability of black holes, we estimate the number of black hole binaries detected by Gaia and their distributions with respect to the black hole mass for several models with different parameters. We find that $\sim 200-1000$ black hole binaries will be detected by Gaia during its 5 years operation. The shape of distribution function of the black hole mass is affected most severely by the relation between the zero-age main sequence (ZAMS) stellar mass and the black hole mass in parameters adopted in this paper, which implies that black holes detected with Gaia enables us to constrain the mass relation.