Chandra detection of XTE J1650-500 in quiescence and the minimum luminosity of black hole X-ray binaries

TL;DR

This paper reports the first detection of the quiescent state of XTE J1650-500 using Chandra, suggesting a possible minimum luminosity threshold for black hole X-ray binaries in quiescence.

Contribution

It provides the first measurement of XTE J1650-500 in quiescence and proposes a potential minimum luminosity for black hole X-ray binaries.

Findings

Detected quiescent X-ray emission from XTE J1650-500.

Luminosity comparable to faintest known black hole binaries.

Suggests a limiting luminosity of around 1e30 erg/s for quiescent black holes.

Abstract

The Galactic black hole X-ray binary XTE J1650-500 entered a quiescent regime following the decline from the 2001-2002 outburst that led to its discovery. Here we report on the first detection of its quiescent counterpart in a 36 ks observation taken in 2007 July with the Chandra X-ray Observatory. The inferred 0.5-10 keV unabsorbed flux is in the range 2.5-5.0x1e-15 erg/s/cm^2. Notwithstanding large distance uncertainties, the measured luminosity is comparable to that of the faintest detected black hole X-ray binaries, all having orbital periods close to the expected bifurcation period between j- and n-driven low-mass X-ray binaries. This suggests that a few 1e30 erg/s might be a limiting luminosity value for quiescent black holes.