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Title: A RADIO-SELECTED BLACK HOLE X-RAY BINARY CANDIDATE IN THE MILKY WAY GLOBULAR CLUSTER M62

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 call 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 ± 1.9 μJy at 6.2 GHz and a flat radio spectrum (α = –0.24 ± 0.42, for S{sub ν} = ν{sup α}). 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, Hα 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 cannotmore » 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.« less
Authors:
;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7]
  1. National Radio Astronomy Observatory, 520 Edgemont Rd, Charlottesville, VA (United States)
  2. Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)
  3. Department of Physics, Texas Tech University, Box 41051, Lubbock, TX 79409-1051 (United States)
  4. International Centre for Radio Astronomy Research, Curtin University, GPO Box U1987, Perth, WA 6845 (Australia)
  5. Department of Physics, University of Alberta, 4-183 CCIS, Edmonton, AB T6G 2E1 (Canada)
  6. Instituto de Astronomia, Universidad Nacional Autonoma de Mexico (UNAM), A. P. 70-264, 04510 (Mexico)
  7. Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States)
Publication Date:
OSTI Identifier:
22270638
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 777; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTRONOMY; ASTROPHYSICS; BLACK HOLES; CORRELATIONS; COSMIC X-RAY SOURCES; FLUX DENSITY; GHZ RANGE; MASS; MILKY WAY; NEUTRON STARS; STAR CLUSTERS; TELESCOPES