An Isolated Stellar-Mass Black Hole Detected Through Astrometric Microlensing
Creators: name: Sahu, Kailash C.
name: Anderson, Jay
name: Casertano, Stefano
name: Bond, Howard E.
name: Udalski, Andrzej
name: Dominik, Martin
name: Calamida, Annalisa
name: Bellini, Andrea
name: Brown, Thomas M.
name: Rejkuba, Marina
name: Bajaj, Varun
name: Kains, Noe
name: Ferguson, Henry C.
name: Fryer, Chris L.
name: Yock, Philip
name: Mroz, Przemek
name: Kozlowski, Szymon
name: Pietrukowicz, Pawel
name: Poleski, Radek
name: Skowron, Jan
name: Soszynski, Igor
name: Szymanski, Michael K.
name: Ulaczyk, Krzysztof
name: Wyrzykowski, Lukasz
name: Barry, Richard
name: Bennett, David P.
name: Bond, Ian A.
name: Hirao, Yuki
name: Silva, Stela Ishitani
name: Kondo, Iona
name: Koshimoto, Naoki
name: Ranc, Clement
name: Rattenbury, Nicholas J.
name: Sumi, Takahiro
name: Suzuki, Daisuke
name: Tristram, Paul J.
name: Vandorou, Aikaterini
name: Beaulieu, Jean-Philippe
name: Marquette, Jean-Baptiste
name: Cole, Andrew
name: Fouque, Pascal
name: Hill, Kym
name: Dieters, Stefan
name: Coutures, Christian
name: Dominis-Prester, Dijana
name: Bennett, Clara
name: Bachelet, Etienne
name: Menzies, John
name: Alb-row, Michael
name: Pollard, Karen
name: Gould, Andrew
name: Yee, Jennifer
name: Allen, William
name: de Almeida, Leonardo Andrade
name: Christie, Grant
name: Drummond, John
name: Gal-Yam, Avishay
name: Gorbikov, Evgeny
name: Jablonski, Francisco
name: Lee, Chung-Uk
name: Maoz, Dan
name: Manulis, Ilan
name: McCormick, Jennie
name: Natusch, Tim
name: Pogge, Richard W.
name: Shvartzvald, Yossi
name: Jorgensen, Uffe G.
name: Alsubai, Khalid A.
name: Andersen, Michael I.
name: Bozza, Valerio
name: Novati, Sebastiano Calchi
name: Burgdorf, Martin
name: Hinse, Tobias C.
name: Hundertmark, Markus
name: Husser, Tim-Oliver
name: Kerins, Eamonn
name: Longa-Pena, Penelope
name: Mancini, Luigi
name: Penny, Matthew
name: Rahvar, Sohrab
name: Ricci, Davide
name: Sajadian, Sedighe
name: Skottfelt, Jesper
name: Snodgrass, Colin
name: Southworth, John
name: Tregloan-Reed, Jeremy
name: Wambsganss, Joachim
name: Wertz, Olivier
name: Tsapras, Yiannis
name: Street, Rachel A.
name: Bramich, Daniel M.
name: Horne, Keith
name: Steele, Iain A.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: 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 six years, 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 the 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 Msun 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 ~45 km/s, 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: 37 pages, Published in ApJ