An analysis of binary microlensing event OGLE-2015-BLG-0060

Tsapras, Y; Cassan, A; Ranc, C; Bachelet, E; Street, R; Udalski, A; Hundertmark, M; Bozza, V; Beaulieu, J P; Marquette, J B; Euteneuer, E; Bramich, D M; Dominik, M; Figuera Jaimes, R; Horne, K; Mao, S; Menzies, J; Schmidt, R; Snodgrass, Colin; Steele, I A; Wambsganss, J; Mróz, P; Szymański, M K; Soszyński, I; Skowron, J; Pietrukowicz, P; Kozłowski, S; Poleski, R; Ulaczyk, K; Pawlak, M; Jørgensen, U G; Skottfelt, J; Popovas, A; Ciceri, S; Korhonen, H; Kuffmeier, M; Evans, D F; Peixinho, N; Hinse, T C; Burgdorf, M J; Southworth, J; Tronsgaard, R; Kerins, E; Andersen, M I; Rahvar, S; Wang, Y; Wertz, O; Rabus, M; Novati, S Calchi; D’Ago, G; Scarpetta, G; Mancini, L; Abe, F; Asakura, Y; Bennett, D P; Bhattacharya, A; Donachie, M; Evans, P; Fukui, A; Hirao, Y; Itow, Y; Kawasaki, K; Koshimoto, N; Li, M C A; Ling, C H; Masuda, K; Matsubara, Y; Muraki, Y; Miyazaki, S; Nagakane, M; Ohnishi, K; Rattenbury, N; Saito, To; Sharan, A; Shibai, H; Sullivan, D J; Sumi, T; Suzuki, D; Tristram, P J; Yamada, T and Yonehara, A (2019). An analysis of binary microlensing event OGLE-2015-BLG-0060. Monthly Notices of the Royal Astronomical Society, 487(4) pp. 4603–4614.

DOI: https://doi.org/10.1093/mnras/stz1404

Abstract

We present the analysis of stellar binary microlensing event OGLE-2015-BLG-0060 based on observations obtained from 13 different telescopes. Intensive coverage of the anomalous parts of the light curve was achieved by automated follow-up observations from the robotic telescopes of the Las Cumbres Observatory. We show that, for the first time, all main features of an anomalous microlensing event are well covered by follow-up data, allowing us to estimate the physical parameters of the lens. The strong detection of second-order effects in the event light curve necessitates the inclusion of longer-baseline survey data in order to constrain the parallax vector. We find that the event was most likely caused by a stellar binary-lens with masses M⋆1=0.87±0.12M⊙ and M⋆2=0.77±0.11M⊙⁠. The distance to the lensing system is 6.41 ± 0.14 kpc and the projected separation between the two components is 13.85 ± 0.16 AU. Alternative interpretations are also considered.

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