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On the use of Gaia for astrometric microlensing
Astrometric microlensing is a unique tool to directly determine the mass of an individual star(“lens”). By measuring the astrometric shift of a background source in combination with precise predictions of its unlensed position as well as of the lens position, it is possible to determine the mass of the lens with an uncertainty of a few per cent. In this thesis, the prediction of such astrometric microlensing events using the second data release of Gaia is presented, and the possibility of measuring the deflection of these events with Gaia is discussed. In the first part, it was possible to predict 3914 microlensing events between 2010 and 2065 with an expected astrometric shift larger than 0.1 mas. Of these events, 640 have a date of the closest approach between 2020 and 2030. Furthermore, 127 events could be found, which might lead to a photometric magnification larger than 1 mmag. Since the typical timescales of these events are of the order of a few months to years, it might be possible for Gaia to detect the deflections, and to determinethe masses of the lenses. This is investigated in the second part of this thesis. For that purpose, the individual Gaia measurements for 501 events during the Gaia era (2014.5 - 2024.5) were simulated. It is shown that Gaia can detect the astrometric deflection for 114 events by simultaneously fitting the motions of lens and source stars. Furthermore, for 13 and for 34 events Gaia can determine the mass of the lens with a precision better than 15% and 30%, respectively. The results presented in this thesis allow the optimal selection of targets for future observational campaigns.
On the use of Gaia for astrometric microlensing (PDF)
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520 Astronomie
520 Astronomy and allied sciences