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Determination of stellar shape in microlensing event MOA 2002-BLG-33

N. J. Rattenbury·F. Abe·D. P. Bennett·I. A. Bond·J. J. Calitz·A. Claret·K. H. Cook·Y. Furuta·A. Gal-Yam·J-F. Glicenstein·J. B. Hearnshaw·P. H. Hauschildt·P. M. Kilmartin·Y. Kurata·K. Masuda·D. Maoz·Y. Matsubara·P. J. Meintjes·M. Moniez·Y. Muraki·S. Noda·E. O. Ofek·K. Okajima·L. Philpott·S. H. Rhie·T. Sako·D. J. Sullivan·T. Sumi·D. M. Terndrup·P. J. Tristram·J. Wood·T. Yanagisawa·P. C. M. Yock
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Abstract

We report a measurement of the shape of the source star in microlensing event MOA 2002-BLG-33. The lens for this event was a close binary whose centre-of-mass passed almost directly in front of the source star. At this time, the source star was closely bounded on all sides by a caustic of the lens. This allowed the oblateness of the source star to be constrained. We found that a/b = 1.02^{+0.04}_{-0.02} where a and b are its semi-major and semi-minor axes respectively. The angular resolution of this measurement is approximately 0.04 microarcsec. We also report HST images of the event that confirm a previous identification of the source star as an F8-G2 turn-off main-sequence star.

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N. J. Rattenbury, F. Abe, D. P. Bennett, I. A. Bond, J. J. Calitz, A. Claret, K. H. Cook, Y. Furuta, A. Gal-Yam, J-F. Glicenstein, J. B. Hearnshaw, P. H. Hauschildt, P. M. Kilmartin, Y. Kurata, K. Masuda, D. Maoz, Y. Matsubara, P. J. Meintjes, M. Moniez, Y. Muraki, S. Noda, E. O. Ofek, K. Okajima, L. Philpott, S. H. Rhie, T. Sako, D. J. Sullivan, T. Sumi, D. M. Terndrup, P. J. Tristram, J. Wood, T. Yanagisawa, P. C. M. Yock. 2005-06-01. Determination of stellar shape in microlensing event MOA 2002-BLG-33. https://doi.org/10.1051/0004-6361%3A20052858

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