We report the discovery of a candidate stellar-mass black hole in the Milky Way globular cluster M62 .
We detected the black hole candidate , which we term M62-VLA1 , in the core of the cluster using deep radio continuum imaging from the Karl G. Jansky Very Large Array .
M62-VLA1 is a faint source , with a flux density of 18.7 \pm 1.9 \mu Jy at 6.2 GHz and a flat radio spectrum ( \alpha = -0.24 \pm 0.42 , for S _ { \nu } = \nu ^ { \alpha } ) .
M62 is the second Milky Way cluster with a candidate stellar-mass black hole ; unlike the two candidate black holes previously found in the cluster M22 , M62-VLA1 is associated with a Chandra X-ray source , supporting its identification as a black hole X-ray binary .
Measurements of its radio and X-ray luminosity , while not simultaneous , place M62-VLA1 squarely on the well-established radio–X-ray correlation for stellar-mass black holes .
In archival Hubble Space Telescope imaging , M62-VLA1 is coincident with a star near the lower red giant branch .
This possible optical counterpart shows a blue excess , H \alpha emission , and optical variability .
The radio , X-ray , and optical properties of M62-VLA1 are very similar to those for V404 Cyg , one of the best-studied quiescent stellar-mass black holes .
We can not yet rule out alternative scenarios for the radio source , such as a flaring neutron star or background galaxy ; future observations are necessary to determine whether M62-VLA1 is indeed an accreting stellar-mass black hole .