Deep Chandra X-ray observation of the isolated black hole OGLE-2011-BLG-0462

TL;DR

This study used deep Chandra X-ray observations to set stringent upper limits on the X-ray luminosity of the isolated black hole OGLE-2011-BLG-0462, providing insights into its accretion activity.

Contribution

First deep X-ray observation of OGLE-2011-BLG-0462, establishing the most restrictive luminosity upper limit for an isolated black hole to date.

Findings

X-ray luminosity upper limit of 3x10^29 erg/s in 0.5-7 keV range

Luminosity limit is an order of magnitude lower than previous constraints

Results compared with accretion models and other black hole candidates

Abstract

OGLE-2011-BLG-0462 is an isolated black hole of ~7 solar masses at a distance of 1.5 kpc identified thanks to the astrometric microlensing technique. It is the first specimen discovered of the large population of ~10^8 stellar-mass black holes that are believd to wander in the Galaxy. Electromagnetic radiation powered by accretion from the interstellar medium is expected from OGLE-2011-BLG-0462, but has not been detected at any wavelength. We present the results of a deep pointed observation with the Chandra satellite that provides an upper limit of 3x10^29 erg/s on the luminosity of OGLE-2011-BLG-0462 in the 0.5-7 keV energy range. This is about one order of magnitude below the previous limit obtained from shallower observations that serendipitously covered the sky position of this black hole. Our results are briefly compared with models of the source and with the X-ray upper limits for candidate isolated black holes and black holes in wide binary systems.