Interpretation of a short-term anomaly in the gravitational microlensing event MOA-2012-BLG-486

Hwang, K.-H.; Choi, J.-Y.; Bond, I. A.; Sumi, T.; Han, C.; Gaudi, B. S.; Gould, A.; Bozza, V.; Beaulieu, J.-P.; Tsapras, Y.; Abe, F.; Bennett, D. P.; Botzler, C. S.; Chote, P.; Freeman, M.; Fukui, A.; Fukunaga, D.; Harris, P.; Itow, Y.; Koshimoto, N.; Ling, C. H.; Masuda, K.; Matsubara, Y.; Muraki, Y.; Namba, S.; Ohnishi, K.; Rattenbury, N. J.; Saito, To.; Sullivan, D. J.; Sweatman, W. L.; Suzuki, D.; Tristram, P. J.; Wada, K.; Yamai, N.; Yock, P. C. M.; Yonehara, A.; Andrade de Almeida, L.; DePoy, D. L.; Dong, Subo; Jablonski, F.; Jung, Y. K.; Kavka, A.; Lee, C.-U.; Park, H.; Pogge, R. W.; Shin, I.-G.; Yee, J. C.; Albrow, M. D.; Bachelet, E.; Batista, V.; Brillant, S.; Caldwell, J. A. R.; Cassan, A.; Cole, A.; Corrales, E.; Coutures, Ch.; Dieters, S.; Dominis Prester, D.; Donatowicz, J.; Fouqué, P.; Greenhill, J.; Jørgensen, U. G.; Kane, S. R.; Kubas, D.; Marquette, J.-B.; Martin, R.; Meintjes, P.; Menzies, J.; Pollard, K. R.; Williams, A.; Wouters, D.; Bramich, D. M.; Dominik, M.; Horne, K.; Browne, P.; Hundertmark, M.; Ipatov, S.; Kains, N.; Snodgrass, Colin; Steele, I. A. and Street, R. A. (2013). Interpretation of a short-term anomaly in the gravitational microlensing event MOA-2012-BLG-486. Astrophysical Journal, 778(1), article no. 55.



A planetary microlensing signal is generally characterized by a short-term perturbation to the standard single lensing light curve. A subset of binary-source events can produce perturbations that mimic planetary signals, thereby introducing an ambiguity between the planetary and binary-source interpretations. In this paper, we present the analysis of the microlensing event MOA-2012-BLG-486, for which the light curve exhibits a short-lived perturbation. Routine modeling not considering data taken in different passbands yields a best-fit planetary model that is slightly preferred over the best-fit binary-source model. However, when allowed for a change in the color during the perturbation, we find that the binary-source model yields a significantly better fit and thus the degeneracy is clearly resolved. This event not only signifies the importance of considering various interpretations of short-term anomalies, but also demonstrates the importance of multi-band data for checking the possibility of false-positive planetary signals.

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