An Isolated Stellar-Mass Black Hole Detected Through Astrometric Microlensing
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 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.
Keywords
Cite
@article{arxiv.2201.13296,
title = {An Isolated Stellar-Mass Black Hole Detected Through Astrometric Microlensing},
author = {Kailash C. Sahu and Jay Anderson and Stefano Casertano and Howard E. Bond and Andrzej Udalski and Martin Dominik and Annalisa Calamida and Andrea Bellini and Thomas M. Brown and Marina Rejkuba and Varun Bajaj and Noe Kains and Henry C. Ferguson and Chris L. Fryer and Philip Yock and Przemek Mroz and Szymon Kozlowski and Pawel Pietrukowicz and Radek Poleski and Jan Skowron and Igor Soszynski and Michael K. Szymanski and Krzysztof Ulaczyk and Lukasz Wyrzykowski and Richard Barry and David P. Bennett and Ian A. Bond and Yuki Hirao and Stela Ishitani Silva and Iona Kondo and Naoki Koshimoto and Clement Ranc and Nicholas J. Rattenbury and Takahiro Sumi and Daisuke Suzuki and Paul J. Tristram and Aikaterini Vandorou and Jean-Philippe Beaulieu and Jean-Baptiste Marquette and Andrew Cole and Pascal Fouque and Kym Hill and Stefan Dieters and Christian Coutures and Dijana Dominis-Prester and Clara Bennett and Etienne Bachelet and John Menzies and Michael Alb-row and Karen Pollard and Andrew Gould and Jennifer Yee and William Allen and Leonardo Andrade de Almeida and Grant Christie and John Drummond and Avishay Gal-Yam and Evgeny Gorbikov and Francisco Jablonski and Chung-Uk Lee and Dan Maoz and Ilan Manulis and Jennie McCormick and Tim Natusch and Richard W. Pogge and Yossi Shvartzvald and Uffe G. Jorgensen and Khalid A. Alsubai and Michael I. Andersen and Valerio Bozza and Sebastiano Calchi Novati and Martin Burgdorf and Tobias C. Hinse and Markus Hundertmark and Tim-Oliver Husser and Eamonn Kerins and Penelope Longa-Pena and Luigi Mancini and Matthew Penny and Sohrab Rahvar and Davide Ricci and Sedighe Sajadian and Jesper Skottfelt and Colin Snodgrass and John Southworth and Jeremy Tregloan-Reed and Joachim Wambsganss and Olivier Wertz and Yiannis Tsapras and Rachel A. Street and Daniel M. Bramich and Keith Horne and Iain A. Steele},
journal= {arXiv preprint arXiv:2201.13296},
year = {2022}
}
Comments
37 pages, Published in ApJ