An Isolated Stellar-mass Black Hole Detected through Astrometric Microlensing
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Date
2022-07-06
Open Access Location
Journal Title
Journal ISSN
Volume Title
Publisher
IOP Publishing on behalf of the American Astronomical Society
Rights
(c) 2022 The Author/s
CC BY 4.0
CC BY 4.0
Abstract
We report the first unambiguous detection and mass measurement of an isolated stellar-mass black hole (BH). We used the Hubble Space Telescope (HST) to carry out precise astrometry of the source star of the long-duration (t E ≃ 270 days), high-magnification microlensing event MOA-2011-BLG-191/OGLE-2011-BLG-0462 (hereafter designated as MOA-11-191/OGLE-11-462), in the direction of the Galactic bulge. HST imaging, conducted at eight epochs over an interval of 6 yr, reveals a clear relativistic astrometric deflection of the background star's apparent position. Ground-based photometry of MOA-11-191/OGLE-11-462 shows a parallactic signature of the effect of Earth's motion on the microlensing light curve. Combining the HST astrometry with the ground-based light curve and the derived parallax, we obtain a lens mass of 7.1 ± 1.3 M ⊙ and a distance of 1.58 ± 0.18 kpc. We show that the lens emits no detectable light, which, along with having a mass higher than is possible for a white dwarf or neutron star, confirms its BH nature. Our analysis also provides an absolute proper motion for the BH. The proper motion is offset from the mean motion of Galactic disk stars at similar distances by an amount corresponding to a transverse space velocity of �1/445 km s-1, suggesting that the BH received a "natal kick"from its supernova explosion. Previous mass determinations for stellar-mass BHs have come from radial velocity measurements of Galactic X-ray binaries and from gravitational radiation emitted by merging BHs in binary systems in external galaxies. Our mass measurement is the first for an isolated stellar-mass BH using any technique.
Description
Keywords
Black holes (162), Gravitational microlensing (672)
Citation
Sahu KC, Anderson J, Casertano S, Bond HE, Udalski A, Dominik M, Calamida A, Bellini A, Brown TM, Rejkuba M, Bajaj V, Kains N, Ferguson HC, Fryer CL, Yock P, Mróz P, Kozłowski S, Pietrukowicz P, Poleski R, Skowron J, Soszyński I, Szymański MK, Ulaczyk K, Wyrzykowski Ł, Barry RK, Bennett DP, Bond IA, Hirao Y, Silva SI, Kondo I, Koshimoto N, Ranc C, Rattenbury NJ, Sumi T, Suzuki D, Tristram PJ, Vandorou A, Beaulieu JP, Marquette JB, Cole A, Fouqué P, Hill K, Dieters S, Coutures C, Dominis-Prester D, Bennett C, Bachelet E, Menzies J, Albrow M, Pollard K, Gould A, Yee JC, Allen W, Almeida LA, Christie G, Drummond J, Gal-Yam A, Gorbikov E, Jablonski F, Lee CU, Maoz D, Manulis I, McCormick J, Natusch T, Pogge RW, Shvartzvald Y, Jørgensen UG, Alsubai KA, Andersen MI, Bozza V, Novati SC, Burgdorf M, Hinse TC, Hundertmark M, Husser TO, Kerins E, Longa-Peña P, Mancini L, Penny M, Rahvar S, Ricci D, Sajadian S, Skottfelt J, Snodgrass C, Southworth J, Tregloan-Reed J, Wambsganss J, Wertz O, Tsapras Y, Street RA, Bramich DM, Horne K, Steele IA. (2022). An Isolated Stellar-mass Black Hole Detected through Astrometric Microlensing. Astrophysical Journal. 933. 1.