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

• Published in: Astronomy and astrophysics (Berlin) Vol. 439; no. 2; pp. 645 - 650
• Main Authors: Rattenbury, N. J., Abe, F., Bennett, D. P., Bond, I. A., Calitz, J. J., Claret, A., Cook, K. H., Furuta, Y., Gal-Yam, A., Glicenstein, J.-F., Hearnshaw, J. B., Hauschildt, P. H., Kilmartin, P. M., Kurata, Y., Masuda, K., Maoz, D., Matsubara, Y., Meintjes, P. J., Moniez, M., Muraki, Y., Noda, S., Ofek, E. O., Okajima, K., Philpott, L., Rhie, S. H., Sako, T., Sullivan, D. J., Sumi, T., Terndrup, D. M., Tristram, P. J., Wood, J., Yanagisawa, T., Yock, P. C. M.
• Format: Journal Article
• Language: English
• Published: Les Ulis EDP Sciences 01.08.2005
• Subjects: Astrophysics; Cosmology and Extra-Galactic Astrophysics; gravitational lensing; Physics; Sciences of the Universe; stars: atmospheres; stars: rotation; stars: atmospheres; Center of mass; Close binary stars; Microlenses; Gravitational lensing; Main sequence stars; Stellar rotation; stars: rotation; gravitational lensing
• ISSN: 0004-6361; 1432-0746; 1432-0756
• DOI: 10.1051/0004-6361:20052858

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 $\mu\rm{arcsec}$. 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.