426 research outputs found
An Isolated Stellar-Mass Black Hole Detected Through Astrometric Microlensing
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, 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 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 M_Sun 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 modest 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 ever for an isolated stellar-mass BH using any technique
Women's work and leisure A guide to the Strangers Hall and Bridewell museums
SIGLELD:84/08982(Women's) / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Learn & live Celebrating twenty five years of the Open University
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A partial index of text complexity involving the lexical analysis of rhetorical collectives
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Report of the vice-chancellor 1992
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Report of the Vice-Chancellor 1994
SIGLEAvailable from British Library Document Supply Centre- DSC:7673.825(1994) / BLDSC - British Library Document Supply CentreGBUnited Kingdo
A first review and register of school and college initiated self evaluation activities in the United Kingdom
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Educational guidance A new service for adult learners
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The outcomes of learning from the Social Science Foundation Course Students' understanding of price control
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