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An Isolated Stellar-mass Black Hole Detected through Astrometric Microlensing

Sahu, Kailash C. and Anderson, Jay and Casertano, Stefano and Bond, Howard E. and Udalski, Andrzej and Dominik, Martin and Calamida, Annalisa and Bellini, Andrea and Brown, Thomas M. and Rejkuba, Marina and Bajaj, Varun and Kains, Noé and Ferguson, Henry C. and Fryer, Chris L. and Yock, Philip and Mróz, Przemek and Kozłowski, Szymon and Pietrukowicz, Paweł and Poleski, Radek and Skowron, Jan and Soszyński, Igor and Szymański, Michał K. and Ulaczyk, Krzysztof and Wyrzykowski, Łukasz and Barry, Richard K. and Bennett, David P. and Bond, Ian A. and Hirao, Yuki and Silva, Stela Ishitani and Kondo, Iona and Koshimoto, Naoki and Ranc, Clément and Rattenbury, Nicholas J. and Sumi, Takahiro and Suzuki, Daisuke and Tristram, Paul J. and Vandorou, Aikaterini and Beaulieu, Jean-Philippe and Marquette, Jean-Baptiste and Cole, Andrew and Fouqué, Pascal and Hill, Kym and Dieters, Stefan and Coutures, Christian and Dominis-Prester, Dijana and Bennett, Clara and Bachelet, Etienne and Menzies, John and Albrow, Michael and Pollard, Karen and Gould, Andrew and Yee, Jennifer C. and Allen, William and Almeida, Leonardo A. and Christie, Grant and Drummond, John and Gal-Yam, Avishay and Gorbikov, Evgeny and Jablonski, Francisco and Lee, Chung-Uk and Maoz, Dan and Manulis, Ilan and McCormick, Jennie and Natusch, Tim and Pogge, Richard W. and Shvartzvald, Yossi and Jørgensen, Uffe G. and Alsubai, Khalid A. and Andersen, Michael I. and Bozza, Valerio and Calchi Novati, Sebastiano and Burgdorf, Martin and Hinse, Tobias C. and Hundertmark, Markus and Husser, Tim-Oliver and Kerins, Eamonn and Longa-Peña, Penelope and Mancini, Luigi and Penny, Matthew and Rahvar, Sohrab and Ricci, Davide and Sajadian, Sedighe and Skottfelt, Jesper and Snodgrass, Colin and Southworth, John and Tregloan-Reed, Jeremy and Wambsganss, Joachim and Wertz, Olivier and Tsapras, Yiannis and Street, Rachel A. and Bramich, D. M. and Horne, Keith and Steele, Iain A. (2022) An Isolated Stellar-mass Black Hole Detected through Astrometric Microlensing. Astrophysical Journal, 933 (1). Art. No. 83. ISSN 0004-637X. doi:10.3847/1538-4357/ac739e.

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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 ∼45 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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Sahu, Kailash C.0000-0001-6008-1955
Anderson, Jay0000-0003-2861-3995
Bond, Howard E.0000-0003-1377-7145
Udalski, Andrzej0000-0001-5207-5619
Dominik, Martin0000-0002-3202-0343
Calamida, Annalisa0000-0002-0882-7702
Bellini, Andrea0000-0003-3858-637X
Brown, Thomas M.0000-0002-1793-9968
Rejkuba, Marina0000-0002-6577-2787
Kains, Noé0000-0001-8803-6769
Ferguson, Henry C.0000-0001-7113-2738
Fryer, Chris L.0000-0003-2624-0056
Yock, Philip0000-0001-9716-7752
Mróz, Przemek0000-0001-7016-1692
Kozłowski, Szymon0000-0003-4084-880X
Pietrukowicz, Paweł0000-0002-2339-5899
Poleski, Radek0000-0002-9245-6368
Skowron, Jan0000-0002-2335-1730
Soszyński, Igor0000-0002-7777-0842
Szymański, Michał K.0000-0002-0548-8995
Ulaczyk, Krzysztof0000-0001-6364-408X
Wyrzykowski, Łukasz0000-0002-9658-6151
Barry, Richard K.0000-0003-4916-0892
Bennett, David P.0000-0001-8043-8413
Hirao, Yuki0000-0003-4776-8618
Silva, Stela Ishitani0000-0003-2267-1246
Kondo, Iona0000-0002-3401-1029
Koshimoto, Naoki0000-0003-2302-9562
Ranc, Clément0000-0003-2388-4534
Rattenbury, Nicholas J.0000-0001-5069-319X
Sumi, Takahiro0000-0002-4035-5012
Suzuki, Daisuke0000-0002-5843-9433
Vandorou, Aikaterini0000-0002-9881-4760
Beaulieu, Jean-Philippe0000-0003-0014-3354
Cole, Andrew0000-0003-0303-3855
Fouqué, Pascal0000-0002-1436-7351
Dominis-Prester, Dijana0000-0002-9880-5039
Bachelet, Etienne0000-0002-6578-5078
Albrow, Michael0000-0003-3316-4012
Yee, Jennifer C.0000-0001-9481-7123
Almeida, Leonardo A.0000-0002-3817-6402
Gal-Yam, Avishay0000-0002-3653-5598
Lee, Chung-Uk0000-0003-0043-3925
Maoz, Dan0000-0002-6579-0483
Pogge, Richard W.0000-0003-1435-3053
Shvartzvald, Yossi0000-0003-1525-5041
Jørgensen, Uffe G.0000-0001-7303-914X
Bozza, Valerio0000-0003-4590-0136
Calchi Novati, Sebastiano0000-0002-7669-1069
Burgdorf, Martin0000-0002-5854-4217
Hinse, Tobias C.0000-0001-8870-3146
Hundertmark, Markus0000-0003-0961-5231
Kerins, Eamonn0000-0002-1743-4468
Mancini, Luigi0000-0002-9428-8732
Penny, Matthew0000-0001-7506-5640
Rahvar, Sohrab0000-0002-7084-5725
Ricci, Davide0000-0002-9790-0552
Sajadian, Sedighe0000-0002-2859-1071
Skottfelt, Jesper0000-0003-1310-8283
Snodgrass, Colin0000-0001-9328-2905
Southworth, John0000-0002-3807-3198
Wambsganss, Joachim0000-0002-8365-7619
Wertz, Olivier0000-0003-3849-2285
Tsapras, Yiannis0000-0001-8411-351X
Street, Rachel A.0000-0001-6279-0552
Horne, Keith0000-0003-1728-0304
Additional Information:© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2022 January 28; revised 2022 May 19; accepted 2022 May 24; published 2022 July 6. Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained at STScI, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. Support for this research was provided by NASA through grants from STScI. HST data used in this paper are available from the Mikulski Archive for Space Telescopes at STScI, 82 under proposal IDs 12322, 12670, 12986, 13458, and 14783. This work has made use of data from the European Space Agency (ESA) mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC, Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. The MOA project is supported by JSPS KAK-ENHI grant Nos. JSPS24253004, JSPS26247023, JSPS23340064, JSPS15H00781, JP16H06287, 17H02871, and 19KK0082. We acknowledge the help and dedication of the late Dr. John Greenhill, who, as part of the PLANET collaboration, played a key role in the efforts of collaboration in general, and in particular running the Tasmania observatory operations. K.C.S. spent some time at the European Southern Observatory, Institute for Advanced Study, and Harvard-Smithsonian Center for Astrophysics, where some of this work was done, and thanks them for their hospitality. Ł.W. acknowledges support from the Polish NCN grant Daina No. 2017/27/L/ST9/03221. J.-P.B. acknowledges support by the University of Tasmania through the UTAS Foundation and the endowed Warren Chair in Astronomy, and support by ANR COLD-WORLDS (ANR-18-CE31-0002) at Le Centre National de la Recherche Scientifique (CNRS) in Paris and the Laboratoire d'astrophysique de Bordeaux. U.G.J. acknowledges funding from the European Union H2020-MSCA-ITN-2019 under grant No. 860470 (CHAMELEON) and from the Novo Nordisk Foundation Interdisciplinary Synergy Programme grant no. NNF19OC0057374. L.M. acknowledges support from the "Fondi di Ricerca Scientificad'Ateneo 2021" of the University of Rome "Tor Vergata." D.D.P. acknowledges support by the University of Rijeka through the grant uniri-prirod-18-48. T.C.H. acknowledges financial support from the National Research Foundation (NRF; No. 2019R1I1A1A 01059609). Y.T. acknowledges the support of DFG priority program SPP 1992 "Exploring the Diversity of Extrasolar Planets" (TS 356/3-1). Note added: After our paper was submitted, a study by Lam et al. (2022) that includes an independent investigation of MOA-11-191/OGLE-11-462 was posted on arXiv. We have not used any of the measurements or results from that paper in our analysis. Facilities: HST (WFC3). This research is based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
NASANAS 5-26555
Gaia Multilateral AgreementUNSPECIFIED
Japan Society for the Promotion of Science (JSPS)JSPS24253004
Japan Society for the Promotion of Science (JSPS)JSPS26247023
Japan Society for the Promotion of Science (JSPS)JSPS23340064
Japan Society for the Promotion of Science (JSPS)JSPS15H00781
Japan Society for the Promotion of Science (JSPS)JP16H06287
Japan Society for the Promotion of Science (JSPS)17H02871
Japan Society for the Promotion of Science (JSPS)19KK0082
National Science Centre (Poland)2017/27/L/ST9/03221
University of TasmaniaUNSPECIFIED
Warren Chair in AstronomyUNSPECIFIED
Agence Nationale de la Recherche (ANR)ANR-18-CE31-0002
European Research Council (ERC)860470
NovoNordisk FoundationNNF19OC0057374
University of RomeUNSPECIFIED
University of Rijekauniri-prirod-18-48
National Research Foundation of Korea2019R1I1A1A01059609
Deutsche Forschungsgemeinschaft (DFG)TS 356/3-1
Subject Keywords:Black holes; Gravitational microlensing
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Black holes (162); Gravitational microlensing (672)
Record Number:CaltechAUTHORS:20220725-156601000
Persistent URL:
Official Citation:Kailash C. Sahu et al 2022 ApJ 933 83
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:115826
Deposited By: George Porter
Deposited On:27 Jul 2022 17:11
Last Modified:27 Jul 2022 17:11

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