1111.4032 (J. -Y. Choi et al.)

Characterizing Lenses and Lensed Stars of High-Magnification Gravitational Microlensing Events With Lenses Passing Over Source Stars    [PDF]

J. -Y. Choi, I. -G. Shin, S. -Y. Park, C. Han, A. Gould, T. Sumi, A. Udalski, J. -P. Beaulieu, R. Street, M. Dominik, W. Allen, M. Bos, G. W. Christie, D. L. Depoy, S. Dong, J. Drummond, A. Gal-Yam, B. S. Gaudi, C. B. Henderson, L. -W. Hung, J. Janczak, C. -U. Lee, F. Mallia, A. Maury, J. McCormick, D. McGregor, L. A. G. Monard, D. Moorhouse, J. A. Muñoz, T. Natusch, C. Nelson, B. -G. Park, R. W. Pogge, T. -G. "TG" Tan, G. Thornley, J. C. Yee, F. Abe, E. Barnard, J. Baudry, D. P. Bennett, I. A. Bond, C. S. Botzler, M. Freeman, A. Fukui, K. Furusawa, F. Hayashi, J. B. Hearnshaw, S. Hosaka, Y. Itow, K. Kamiya, P. M. Kilmartin, S. Kobara, A. Korpela, W. Lin, C. H. Ling, S. Makita, K. Masuda, Y. Matsubara, N. Miyake, Y. Muraki, M. Nagaya, K. Nishimoto, K. Ohnishi, T. Okumura, K. Omori, Y. C. Perrott, N. Rattenbury, To. Saito, L. Skuljan, D. J. Sullivan, D. Suzuki, K. Suzuki, W. L. Sweatman, S. Takino, P. J. Tristram, K. Wada, P. C. M. Yock, M. K. Szymański, M. Kubiak, G. Pietrzyński, I. Soszyński, R. Poleski, K. Ulaczyk, Ł. Wyrzykowski, S. Kozłowski, P. Pietrukowicz, M. D. Albrow, E. Bachelett, V. Batista, C. Bennett, R. Bowens-Rubin, S. Brillant, A. Cassan, A. Cole, E. Corrales, Ch. Coutures, S. Dieters, D. Dominis Prester, J. Donatowicz, P. Fouqué, J. Greenhill, S. R. Kane, J. Menzies, K. C. Sahu, J. Wambsganss, A. Williams, M. Zub, A. Allan, D. M. Bramich, P. Browne, N. Clay, S. Fraser, K. Horne, N. Kains, C. Mottram, C. Snodgrass, I. Steele, Y. Tsapras, K. A. Alsubai, V. Bozza, M. J. Burgdorf, S. Calchi Novati, P. Dodds, S. Dreizler, F. Finet, T. Gerner, M. Glitrup, F. Grundahl, S. Hardis, K. Harpsøe, T. C. Hinse, M. Hundertmark, U. G. Jørgensen, E. Kerins, C. Liebig, G. Maier, L. Mancini, M. Mathiasen, M. T. Penny, S. Proft, S. Rahvar, D. Ricci, G. Scarpetta, S. Schäfer, F. Schönebeck, J. Skottfelt, J. Surdej, J. Southworth, F. Zimmer

We present the analysis of the light curves of 9 high-magnification gravitational microlensing events with lenses passing over source stars, including OGLE-2004-BLG-254, MOA-2007-BLG-176, MOA-2007-BLG-233/OGLE-2007-BLG-302, MOA-2009-BLG-174, MOA-2010-BLG-436, MOA-2011-BLG-093, MOA-2011-BLG-274, OGLE-2011-BLG-0990/MOA-2011-BLG-300, and OGLE-2011-BLG-1101/MOA-2011-BLG-325. For all events, we measure the linear limb-darkening coefficients of the surface brightness profile of source stars by measuring the deviation of the light curves near the peak affected by the finite-source effect. For 8 events, we measure the Einstein radii and the lens-source relative proper motions. Among them, 6 events (OGLE-2004-BLG-254, MOA-2007-BLG-176, MOA-2007-BLG-233/OGLE-2007-BLG-302, MOA-2011-BLG-093, MOA-2011-BLG-274, and OGLE-2011-BLG-0990/MOA-2011-BLG-300) are found to have Einstein radii less than 0.2 mas, making the lenses candidates of very low-mass stars or brown dwarfs. For MOA-2011-BLG-274, especially, the small Einstein radius of $\theta_{\rm E}\sim 0.09$ mas combined with the short time scale of $t_{\rm E}\sim 3.1$ days suggests the possibility that the lens is a free-floating planet. For MOA-2009-BLG-174, we measure the lens parallax and thus uniquely determine the physical parameters of the lens. We also find that the measured lens mass of $\sim 0.8\ M_\odot$ is consistent with that of a star blended with the source, suggesting that the blend is probably the lens. For the systematic integration of information that can be extracted from a sample of events with lenses passing over source stars, we also present the results of 8 other events that were previously analyzed.

View original: http://arxiv.org/abs/1111.4032