Assessing LSST's ability to hunt LIGO black holes with microlensing


Abrams NS, et. al. Assessing LSST's ability to hunt LIGO black holes with microlensing. Astronomical Society Meeting Abstracts #235. 2020 :159.01.


Gravitational microlensing is a powerful tool to study invisible objects, such as black holes, in the Milky Way. By monitoring highly populated areas like the Galactic bulge region, one can observe a variety of microlensing events due to brown dwarfs, main-sequence stars, white dwarfs, neutron stars, and black holes. We model the microlensing event rates with source stars in the Galactic bulge region using standard spatial and velocity distributions of stars in the Galactic bulge and disk regions. We observe that if black holes have an extended Salpeter-like mass function (as indicated by the recent LIGO binary-black hole gravitational wave events) and a similar velocity and spatial structure to stars, the population leads to a distinct increase in the microlensing event rate with Einstein crossing time on the order of 100 days. By looking toward the Galactic bulge region and observing on the order of 108 stars, we could potentially observe this excess of microlensing events. The Large Synoptic Survey Telescope (LSST) holds the potential to make these observations, though the success of observing microlensing events depends on the cadence of the telescope. We evaluate the efficacy of potential LSST cadences as either a trigger or a measurer of the light curves of black hole microlensing.