MOA-2010-BLG-523: "Failed Planet" = RS CVn Star

Gould, A.; Yee, J. C.; Bond, I. A.; Udalski, A.; Han, C.; Jørgensen, U. G.; Greenhill, J.; Tsapras, Y.; Pinsonneault, M. H.; Bensby, T.; Allen, W.; Almeida, L. A.; Bos, M.; Christie, G. W.; Depoy, D. L.; Subo, Dong; Gaudi, B. S.; Hung, L. W.; Jablonski, F.; Lee, C. U.; Mccormick, J.; Moorhouse, D.; Muñoz, J. A.; Natusch, T.; Nola, M.; Pogge, R. W.; Skowron, J.; Thornley, G.; Abe, F.; Bennett, D. P.; Botzler, C. S.; Chote, P.; Freeman, M.; Fukui, A.; Furusawa, K.; Harris, P.; Itow, Y.; Ling, C. H.; Masuda, K.; Matsubara, Y.; Miyake, N.; Ohnishi, K.; Rattenbury, N. J.; Saito, T. o.; Sullivan, D. J.; Sumi, T.; Suzuki, D.; Sweatman, W. L.; Tristram, P. J.; Wada, K.; Yock, P. C. M.; Szymański, M. K.; Soszyński, I.; Kubiak, M.; Poleski, R.; Ulaczyk, K.; Pietrzyński, G.; Wyrzykowski, Ł.; Alsubai, K. A.; Bozza, Valerio; Browne, P.; Burgdorf, M. J.; Calchi Novati, S.; Dodds, P.; Dominik, M.; Finet, F.; Gerner, T.; Hardis, S.; Harpsøe, K.; Hessman, F. V.; Hinse, T. C.; Hundertmark, M.; Kains, N.; Kerins, E.; Liebig, C.; Mancini, L.; Mathiasen, M.; Penny, M. T.; Proft, S.; Rahvar, S.; Ricci, D.; Sahu, K. C.; Scarpetta, Gaetano; Schäfer, S.; Schönebeck, F.; Snodgrass, C.; Southworth, J.; Surdej, J.; Wambsganss, J.; Street, R. A.; Horne, K.; Bramich, D. M.; Steele, I. A.; Albrow, M. D.; Bachelet, E.; Batista, V.; Beatty, T. G.; Beaulieu, J. P.; Bennett, C. S.; Bowens Rubin, R.; Brillant, S.; Caldwell, J. A. R.; Cassan, A.; Cole, A. A.; Corrales, E.; Coutures, C.; Dieters, S.; Dominis Prester, D.; Donatowicz, J.; Fouqué, P.; Henderson, C. B.; Kubas, D.; Marquette, J. B.; Martin, R.; Menzies, J. W.; Shappee, B.; Williams, A.; van Saders, J.; Zub, M.

doi:10.1088/0004-637X/763/2/141

The Galactic bulge source MOA-2010-BLG-523S exhibited short-term deviations from a standard microlensing light curve near the peak of an A max ~ 265 high-magnification microlensing event. The deviations originally seemed consistent with expectations for a planetary companion to the principal lens. We combine long-term photometric monitoring with a previously published high-resolution spectrum taken near peak to demonstrate that this is an RS CVn variable, so that planetary microlensing is not required to explain the light-curve deviations. This is the first spectroscopically confirmed RS CVn star discovered in the Galactic bulge.