An X-ray emitting black hole in a globular cluster

TL;DR

This paper reports the discovery of a black hole in a globular cluster through combined optical and X-ray observations, highlighting its brightness, variability, and spectral features indicative of accretion activity.

Contribution

It provides the first strong evidence for a black hole in a globular cluster using multi-wavelength data, including optical spectrum analysis.

Findings

Identification of an extremely bright, variable X-ray source consistent with a black hole

Optical spectrum confirms the source as a globular cluster with broad [O III] emission

Detection of outflow signatures driven by accretion

Abstract

We present optical and X-ray data for the first object showing strong evidence for being a black hole in a globular cluster. We show the initial X-ray light curve and X-ray spectrum which led to the discovery that this is an extremely bright, highly variable source, and thus must be a black hole. We present the optical spectrum which unambiguously identifies the optical counterpart as a globular cluster, and which shows a strong, broad [O III] emission line, most likely coming from an outflow driven by the accreting source.