MOA-2010-BLG-311: A Planetary Candidate below the Threshold of Reliable Detection

Yee, J. C.; Hung, L. W.; Bond, I. A.; Allen, W.; Monard, L. A. G.; Albrow, M. D.; Fouqué, P.; Dominik, M.; Tsapras, Y.; Udalski, A.; Gould, A.; Zellem, R.; Bos, M.; Christie, G. W.; Depoy, D. L.; Dong, Subo; Drummond, J.; Gaudi, B. S.; Gorbikov, E.; Han, C.; Kaspi, S.; Klein, N.; Lee, C. U.; Maoz, D.; Mccormick, J.; Moorhouse, D.; Natusch, T.; Nola, M.; Park, B. G.; Pogge, R. W.; Polishook, D.; Shporer, A.; Shvartzvald, Y.; 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.; 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.; Greenhill, J.; Henderson, C. B.; Kubas, D.; Marquette, J. B.; Martin, R.; Menzies, J. W.; Shappee, B.; Williams, A.; Wouters, D.; Van Saders, J.; Zub, M.; Street, R. A.; Horne, K.; Bramich, D. M.; Steele, I. A.; Alsubai, K. A.; Bozza, Valerio; Browne, P.; Burgdorf, M. J.; Calchi Novati, Sebastiano; Dodds, P.; Finet, F.; Gerner, T.; Hardis, S.; Harpsøe, K.; Hessman, F. V.; Hinse, T. C.; Hundertmark, M.; Jørgensen, U. G.; Kains, N.; Kerins, E.; Liebig, C.; Mancini, Luigi; 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.

doi:10.1088/0004-637X/769/1/77

We analyze MOA-2010-BLG-311, a high magnification (A max > 600) microlensing event with complete data coverage over the peak, making it very sensitive to planetary signals. We fit this event with both a point lens and a two-body lens model and find that the two-body lens model is a better fit but with only Δχ2 ~ 80. The preferred mass ratio between the lens star and its companion is q = 10–3.7 ± 0.1, placing the candidate companion in the planetary regime. Despite the formal significance of the planet, we show that because of systematics in the data the evidence for a planetary companion to the lens is too tenuous to claim a secure detection. When combined with analyses of other high-magnification events, this event helps empirically define the threshold for reliable planet detection in high-magnification events, which remains an open question.