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OGLE-2017-BLG-1186: first application of asteroseismology and Gaussian processes to microlensing

Li, S-S; Zang, W; Udalski, A; Shvartzvald, Y; Huber, D; Lee, C-U; Sumi, T; Gould, A; Mao, S; Fouqué, P; Wang, T; Dong, S; Jørgensen, U G; Cole, A; Mróz, P; Szymański, M K; Skowron, J; Poleski, R; Soszyński, I; Pietrukowicz, P; Kozłowski, S; Ulaczyk, K; Rybicki, K A; Iwanek, P; Yee, J C; Novati, S Calchi; Beichman, C A; Bryden, G; Carey, S; Gaudi, B S; Henderson, C B; Zhu, W; Albrow, M D; Chung, S-J; Han, C; Hwang, K-H; Jung, Y K; Ryu, Y-H; Shin, I-G; Cha, S-M; Kim, D-J; Kim, H-W; Kim, S-L; Lee, D-J; Lee, Y; Park, B-G; Pogge, R W; Bond, I A; Abe, F; Barry, R; Bennett, D P; Bhattacharya, A; Donachie, M; Fukui, A; Hirao, Y; Itow, Y; Kondo, I; Koshimoto, N; Li, M C A; Matsubara, Y; Muraki, Y; Miyazaki, S; Nagakane, M; Ranc, C; Rattenbury, N J; Suematsu, H; Sullivan, D J; Suzuki, D; Tristram, P J; Yonehara, A; Christie, G; Drummond, J; Green, J; Hennerley, S; Natusch, T; Porritt, I; Bachelet, E; Maoz, D; Street, R A; Tsapras, Y; Bozza, V; Dominik, M; Hundertmark, M; Peixinho, N; Sajadian, S; Burgdorf, M J; Evans, D F; Jaimes, R Figuera; Fujii, Y I; Haikala, L K; Helling, C; Henning, T; Hinse, T C; Mancini, L; Longa-Pe na, P; Rahvar, S; Rabus, M; Skottfelt, J.; Snodgrass, C.; Southworth, J; Unda-Sanzana, E; Essen, C von; Beaulieu, J-P; Blackman, J and Hill, K (2019). OGLE-2017-BLG-1186: first application of asteroseismology and Gaussian processes to microlensing. Monthly Notices of the Royal Astronomical Society, 488(3) pp. 3308–3323.

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We present the analysis of the event OGLE-2017-BLG-1186 from the 2017 Spitzer microlensing campaign. This is a remarkable microlensing event because its source is photometrically bright and variable, which makes it possible to perform an asteroseismic analysis using ground-based data. We find that the source star is an oscillating red giant with average timescale of ∼9 days. The asteroseismic analysis also provides us source properties including the source angular size (∼27μas) and distance (∼11.5 kpc), which are essential for inferring the properties of the lens. When fitting the light curve, we test the feasibility of Gaussian Processes (GPs) in handling the correlated noise caused by the variable source. We find that the parameters from the GP model are generally more loosely constrained than those from the traditional χ2 minimization method. We note that this event is the first microlensing system for which asteroseismology and GPs have been used to account for the variable source. With both finite-source effect and microlens parallax measured, we find that the lens is likely a ∼0.045 M brown dwarf at distance ∼9.0 kpc, or a ∼0.073 M ultracool dwarf at distance ∼9.8 kpc. Combining the estimated lens properties with a Bayesian analysis using a Galactic model, we find a 35% probability for the lens to be a bulge object and 65% to be a background disk object.

Item Type: Journal Item
Copyright Holders: 2019 The Authors
ISSN: 1365-2966
Keywords: asteroseismology; gravitational lensing: micro; stars: fundamental parameters; stars: oscillations
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Physical Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Item ID: 62533
SWORD Depositor: Jisc Publications-Router
Depositing User: ORO Import
Date Deposited: 22 Jul 2019 08:23
Last Modified: 26 Sep 2019 05:39
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