Black Hole Binaries in Quiescence

TL;DR

This paper reviews what is known about black hole binary systems in quiescence, emphasizing its importance for understanding system parameters, accretion processes, and binary evolution, especially in the context of gravitational wave astronomy.

Contribution

It synthesizes current knowledge on quiescent black hole binaries and highlights the significance of this state for astrophysical measurements and evolution studies.

Findings

Longer distance to GRO J1655-40 is supported

Quiescence allows robust binary parameter determination

Understanding quiescence aids in binary evolution and gravitational wave studies

Abstract

I discuss some of what is known and unknown about the behavior of black hole binary systems in the quiescent accretion state. Quiescence is important for several reasons: 1) the dominance of the companion star in the optical and IR wavelengths allows the binary parameters to be robustly determined - as an example, we argue that the longer proposed distance to the X-ray source GRO J1655-40 is correct; 2) quiescence represents the limiting case of an extremely low accretion rate, in which both accretion and jets can be observed; 3) understanding the evolution and duration of the quiescent state is a key factor in determining the overall demographics of X-rary binaries, which has taken on a new importance in the era of gravitational wave astronomy.