Title: Predicting Gravitational Lensing by Stellar Remnants,
Abstract: Gravitational lensing provides a means to measure mass that does not rely on
detecting and analysing light from the lens itself. Compact objects are ideal
gravitational lenses, because they have relatively large masses and are dim. In
this paper we describe the prospects for predicting lensing events generated by
the local population of compact objects, consisting of 250 neutron stars, 5
black holes, and approximately 35,000 white dwarfs. By focusing on a population
of nearby compact objects with measured proper motions and known distances from
us, we can measure their masses by studying the characteristics of any lensing
event they generate. Here we concentrate on shifts in the position of a
background source due to lensing by a foreground compact object. With HST,
JWST, and Gaia, measurable centroid shifts caused by lensing are relatively
frequent occurrences. We find that 30-50 detectable events per decade are
expected for white dwarfs. Because relatively few neutron stars and black holes
have measured distances and proper motions, it is more difficult to compute
realistic rates for them. However, we show that at least one isolated neutron
star has likely produced detectable events during the past several decades.
This work is particularly relevant to the upcoming data releases by the Gaia
mission and also to data that will be collected by JWST. Monitoring predicted
microlensing events will not only help to determine the masses of compact
objects, but will also potentially discover dim companions to these stellar
remnants, including orbiting exoplanets.