Probing the atmosphere of a solar-like star by galactic microlensing at high magnification

TL;DR

This study used high-magnification microlensing to measure limb darkening of a solar-like star, achieving the first such measurement with an effective angular resolution under 1 micro-arcsecond, confirming stellar atmosphere models.

Contribution

First microlensing-based measurement of limb darkening for a solar-like star with high angular resolution, validating stellar atmosphere theories.

Findings

Limb darkening profiles agree with models within ~4%

Effective angular resolution achieved is <1 micro-arcsecond

Lens identified as a close binary system passing in front of the star

Abstract

We report a measurement of limb darkening of a solar-like star in the very high magnification microlensing event MOA 2002-BLG-33. A 15 hour deviation from the light curve profile expected for a single lens was monitored intensively in V and I passbands by five telescopes spanning the globe. Our modelling of the light curve showed the lens to be a close binary system whose centre-of-mass passed almost directly in front of the source star. The source star was identified as an F8-G2 main sequence turn-off star. The measured stellar profiles agree with current stellar atmosphere theory to within ~4% in two passbands. The effective angular resolution of the measurements is <1 micro-arcsec. These are the first limb darkening measurements obtained by microlensing for a Solar-like star.