Letter to the Editor

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

¹ Solar Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-01, Japan
² Department of Physics, Notre Dame University, Notre Dame, IN 46556, USA
³ Institute for Astronomy, University of Edinburgh, Edinburgh, EH9 3HJ, UK
⁴ Department of Physics, University of the Free State, Bloemfontein, South Africa
⁵ Instituto de Astrofísica de Andalucía, CSIC, Apartado 3004, 18080 Granada, Spain
⁶ Institute for Geophysics and Planetary Physics, Lawrence Livermore National Laboratory, CA 94563, USA
⁷ School of Physics and Astronomy, Tel-Aviv University, Tel-Aviv 69978, Israel
⁸ CEA, DSM, DAPNIA, Centre d'Études de Saclay, 91191 Gif-sur-Yvette Cedex, France
⁹ Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch, New Zealand
¹⁰ Universität Hamburg, Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany
¹¹ Faculty of Science, University of Auckland, Private Bag 92019, Auckland, New Zealand
¹² School of Chemical and Physical Sciences, Victoria University, PO Box 600, Wellington, New Zealand
¹³ Department of Astrophysical Sciences, Princeton University, Princeton NJ 08544, USA
¹⁴ Department of Astronomy, Ohio State University, Columbus OH 43210, USA

Corresponding author: I. A. Bond, iab@roe.ac.uk

Received: 2 July 2003
Accepted: January 1900

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 μas. These are the first limb darkening measurements obtained by microlensing for a Solar-like star.