Planetesimal Disk Microlensing

TL;DR

This paper explores how gravitational microlensing by planetesimal disks around stars can reveal small bodies, providing a new method to study debris disks and their composition through detectable light curve residuals.

Contribution

It introduces a model for planetesimal disk microlensing and analyzes its observational signatures, highlighting the potential to detect small bodies below Earth mass.

Findings

Microlensing can detect planetesimals several orders of magnitude below Earth mass.

Detection sensitivity depends on photometric precision and source star size.

Nearby planetesimals are more detectable due to mass distribution effects.

Abstract

Motivated by debris disk studies, we investigate the gravitational microlensing of background starlight by a planetesimal disk around a foreground star. We use dynamical survival models to construct a plausible example of a planetesimal disk and study its microlensing properties using established ideas of microlensing by small bodies. When a solar-type source star passes behind a planetesimal disk, the microlensing light curve may exhibit short-term, low-amplitude residuals caused by planetesimals several orders of magnitude below Earth mass. The minimum planetesimal mass probed depends on the photometric sensitivity and the size of the source star, and is lower when the planetesimal lens is located closer to us. Planetesimal lenses may be found more nearby than stellar lenses because the steepness of the planetesimal mass distribution changes how the microlensing signal depends on the lens/source distance ratio. Microlensing searches for planetesimals require essentially continuous monitoring programs that are already feasible and can potentially set constraints on models of debris disks, the supposed extrasolar analogues of Kuiper belts.