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Microlensing mass measurement from images of rotating gravitational arcs

Abstract : Gravitational microlensing1 is a powerful technique for measuring the mass of isolated and faint or non-luminous objects in the Milky Way2,3. In most cases, however, additional observations to the photometric light curve are required to measure accurately the mass of the microlens. Long-baseline optical/infrared interferometry provides a new and efficient way to deliver such independent constraints4-7, as demonstrated recently by first interferometric observations in microlensing event TCP J05074264+2447555 (`Kojima-1')8. Here we report real-time observations of gravitationally lensed arcs in rotation around a microlens, Gaia19bld9, made with the PIONIER instrument10 at the Very Large Telescope Interferometer. Our data allowed us to determine the angular separation and length of the arcs, as well as their rotation rate. Combining these measurements with ground-based photometric data enabled the determination of the microlens mass, M = 1.147 ± 0.029 M, to a very high accuracy. We anticipate interferometric microlensing to play an important future role in the mass and distance determination of isolated stellar-mass black holes11-13 in the Galaxy, which cannot be addressed by any other technique.
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Contributor : Nathalie POTHIER Connect in order to contact the contributor
Submitted on : Monday, June 27, 2022 - 9:06:44 AM
Last modification on : Wednesday, August 3, 2022 - 3:59:04 AM

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Arnaud Cassan, Clément Ranc, Olivier Absil, Łukasz Wyrzykowski, Krzysztof A. Rybicki, et al.. Microlensing mass measurement from images of rotating gravitational arcs. Nature Astronomy, 2022, 6, pp.121-128. ⟨10.1038/s41550-021-01514-w⟩. ⟨insu-03705389⟩



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