Microlens Surveys are a Powerful Probe of Asteroids

TL;DR

This paper demonstrates how microlensing surveys can significantly expand the sample of well-characterized asteroids, especially small ones, by providing precise orbits and rotation periods, and also proposes using asteroid data to study Galactic proper motions.

Contribution

It introduces a method to use microlensing survey data to obtain detailed asteroid properties and suggests leveraging asteroid astrometry for Galactic dynamics studies.

Findings

Microlensing data can yield a large, precise asteroid sample including small asteroids down to 1 km.

Approximately 6% of all asteroids with I<18.1 near the ecliptic can be characterized.

Astrometry from microlensing surveys can be used to measure proper-motion gradients across the Galactic bar.

Abstract

While of order a million asteroids have been discovered, the number in rigorously controlled samples that have precise orbits and rotation periods, as well as well-measured colors, is relatively small. In particular, less than a dozen main-belt asteroids with estimated diameters D<3 km, have excellent rotation periods. We show how existing and soon-to-be-acquired microlensing data can yield a large asteroid sample with precise orbits and rotation periods, which will include roughly 6% of all asteroids with maximum brightness I<18.1 and lying within 10 deg of the ecliptic. This sample will be dominated by small and very small asteroids, down to D~1 km. We also show how asteroid astrometry could turn current narrow-angle OGLE proper motions of bulge stars into wide-angle proper motions. This would enable one to measure the proper-motion gradient across the Galactic bar.