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

Y. Tsapras, A. Cassan, C. Ranc, E. Bachelet, R. Street, A. Udalski, M. Hundertmark, V. Bozza, J. P. Beaulieu, J. B. Marquette, E. Euteneuer, D. M. Bramich, M. Dominik, R. Figuera Jaimes, K. Horne, S. Mao, J. Menzies, R. Schmidt, C. Snodgrass, I. A. SteeleJ. Wambsganss, P. Mróz, M. K. Szymański, I. Soszyński, J. Skowron, P. Pietrukowicz, S. Kozłowski, R. Poleski, K. Ulaczyk, M. Pawlak, U. G. Jørgensen, J. Skottfelt, A. Popovas, S. Ciceri, H. Korhonen, M. Kuffmeier, D. F. Evans, N. Peixinho, T. C. Hinse, M. J. Burgdorf, J. Southworth, R. Tronsgaard, E. Kerins, M. I. Andersen, S. Rahvar, Y. Wang, O. Wertz, M. Rabus, S. Calchi Novati, G. D'Ago, G. Scarpetta, L. Mancini, F. Abe, Y. Asakura, D. P. Bennett, A. Bhattacharya, M. Donachie, P. Evans, A. Fukui, Y. Hirao, Y. Itow, K. Kawasaki, N. Koshimoto, M. C. A. Li, C. H. Ling, K. Masuda, Y. Matsubara, Y. Muraki, S. Miyazaki, M. Nagakane, K. Ohnishi, N. Rattenbury, To. Saito, A. Sharan, H. Shibai, D. J. Sullivan, T. Sumi, D. Suzuki, P. J. Tristram, T. Yamada, A. Yonehara

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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.
Original languageEnglish
Pages (from-to)4603–4614
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
Early online date30 May 2019
Publication statusPublished - Aug 2019


  • Gravitational lensing: micro
  • Methods: observational
  • Techniques: photometric
  • Galaxy: bulge


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