Astrometric detection of binary asteroids

TL;DR

This paper explores a novel astrometric method to detect binary asteroids by observing the wobble in their light center, using simulated and real Gaia data, revealing potential signals and discussing limitations.

Contribution

It introduces a forward model for astrometric detection of binary asteroids and evaluates its effectiveness with Gaia data, highlighting its potential and challenges.

Findings

No significant binary signals in Gaia DR2 data.

Possible binary signal detected in asteroid (4337) Arecibo with a 16.26 hr period.

Marginal excess of astrometric noise in known binary asteroids.

Abstract

Binary asteroids probe thermal-radiation effects on the main-belt asteroids' evolution. We discuss the possibility of detecting binary minor planet systems by the astrometric wobble of the center-of-light around the center-of-mass. This method enables the exploration of the phase-space of binary asteroids, which is difficult to explore using common detection techniques. We describe a forward model that projects the center-of-light position with respect to the center-of-mass, as it is seen by the observer. We study the performance of this method using simulated Gaia-like data. We apply the astrometric method to a subset of the Gaia DR2 Solar System catalog and find no significant evidence of binary asteroids. This is likely because the Gaia DR2 removed astrometric outliers, which in our case may be due to astrophysical signals. Applying this method to binary asteroid (4337) Arecibo, for which Gaia DR3 reported a possible astrometric signal with a period of P = 32.85+/-0.38 hr, reveals a possible 2.2-sigma solution with a period of 16.26 hr (about half the reported period). We find a small, marginally significant, excess of astrometric noise in the known binary asteroid population from Pravec et al. relative to the entire asteroid population in the Gaia DR2 Solar System catalog. We also discuss some caveats like precession and asteroid rotation.