Weak Microlensing

TL;DR

Weak microlensing occurs when a nearby star causes a small, time-dependent lensing effect on a background galaxy, potentially enabling mass measurements of low-mass stars and brown dwarfs.

Contribution

This paper explores the feasibility of using weak microlensing to measure the masses of low-mass stars and brown dwarfs, a novel application of gravitational lensing.

Findings

A star can cause measurable weak microlensing effects at 10 Einstein radii.

Approximately one galaxy per year comes close enough to a nearby star for potential measurement.

Weak microlensing could be a useful method for weighing low-mass stellar objects.

Abstract

A nearby star having a near-transit of a galaxy will cause a time-dependent weak lensing of the galaxy. Because the effect is small, we refer to this as weak microlensing. This could provide a useful method to weigh low-mass stars and brown dwarfs. We examine the feasibility of measuring masses in this way and we find that a star causes measurable weak microlensing in a galaxy even at 10 Einstein radii away. Of order one magnitude I < 25 galaxy comes close enough to one or other of the ~100 nearest stars per year.