Data: 20.01.2026

Krzysztof Rybicki (OAUW,PL)

Astrometric microlensing in surveys

Streszczenie:
Astrometric microlensing arises when the gravitational field of a foreground object causes a small, time-dependent shift in the apparent position of a background star. Because this signal depends directly on the lens mass, it offers a unique way to detect and weigh objects that emit little or no light, such as stellar remnants and isolated stellar-mass black holes. Until now, astrometric microlensing measurements have been limited mainly to carefully selected events observed with dedicated follow-up. With two major milestones occurring this year - the launch of the Nancy Grace Roman Space Telescope and the release of Gaia DR4 astrometric time series - this situation is beginning to change. The combination of long temporal baselines, dense sampling, and high-precision astrometry makes it possible to search for astrometric microlensing signals directly within large survey data sets, rather than relying exclusively on targeted observations. In this presentation, we discuss how astrometric microlensing can be studied in a survey context using existing and upcoming data. We examine the detectability of astrometric signals in long-baseline, seeing-limited ground-based data from KMT, assess the gains from combining Gaia astrometry with dense ground-based photometry from OGLE, and outline expectations for astrometric microlensing with the Roman Space Telescope, which is expected to substantially increase the number of measurable events. This shift from follow-up-driven measurements to routine survey detections opens the door to statistically robust mass measurements and population studies across the Galaxy.