OGLE-2017-BLG-1186: first application of asteroseismology and Gaussian processes to microlensing
Creators: name: Li, Shun-Sheng
name: Zang, Weicheng
name: Udalski, Andrzej
name: Shvartzvald, Yossi
name: Huber, Daniel
name: Lee, Chung-Uk
name: Sumi, Takahiro
name: Gould, Andrew
name: Mao, Shude
name: Fouqué, Pascal
name: Wang, Tianshu
name: Dong, Subo
name: Jørgensen, Uffe G.
name: Cole, Andrew
name: Mróz, Przemek
name: Szymański, Michał K.
name: Skowron, Jan
name: Poleski, Radosław
name: Soszyński, Igor
name: Pietrukowicz, Paweł
name: Kozłowski, Szymon
name: Ulaczyk, Krzysztof
name: Rybicki, Krzysztof A.
name: Iwanek, Patryk
name: Yee, Jennifer C.
name: Novati, Sebastiano Calchi
name: Beichman, Charles A.
name: Bryden, Geoffery
name: Carey, Sean
name: Gaudi, B. Scott
name: Henderson, Calen B.
name: Zhu, Wei
name: Albrow, Michael D.
name: Chung, Sun-Ju
name: Han, Cheongho
name: Hwang, Kyu-Ha
name: Jung, Youn Kil
name: Ryu, Yoon-Hyun
name: Shin, In-Gu
name: Cha, Sang-Mok
name: Kim, Dong-Jin
name: Kim, Hyoun-Woo
name: Kim, Seung-Lee
name: Lee, Dong-Joo
name: Lee, Yongseok
name: Park, Byeong-Gon
name: Pogge, Richard W.
name: Bond, Ian A.
name: Abe, Fumio
name: Barry, Richard
name: Bennett, David P.
name: Bhattacharya, Aparna
name: Donachie, Martin
name: Fukui, Akihiko
name: Hirao, Yuki
name: Itow, Yoshitaka
name: Kondo, Iona
name: Koshimoto, Naoki
name: Li, Man Cheung Alex
name: Matsubara, Yutaka
name: Muraki, Yasushi
name: Miyazaki, Shota
name: Nagakane, Masayuki
name: Ranc, Clément
name: Rattenbury, Nicholas J.
name: Suematsu, Haruno
name: Sullivan, Denis J.
name: Suzuki, Daisuke
name: Tristram, Paul J.
name: Yonehara, Atsunori
name: Christie, Grant
name: Drummond, John
name: Green, Jonathan
name: Hennerley, Steve
name: Natusch, Tim
name: Porritt, Ian
name: Bachelet, Etienne
name: Maoz, Dan
name: Street, Rachel A.
name: Tsapras, Yiannis
name: Bozza, Valerio
name: Dominik, Martin
name: Hundertmark, Markus
name: Peixinho, Nuno
name: Sajadian, Sedighe
name: Burgdorf, Martin J.
name: Evans, Daniel F.
name: Jaimes, Roberto Figuera
name: Fujii, Yuri I.
name: Haikala, Lauri K.
name: Helling, Christiane
name: Henning, Thomas
name: Hinse, Tobias C.
name: Mancini, Luigi
name: Longa-Peña, Penelope
name: Rahvar, Sohrab
name: Rabus, Markus
name: Skottfelt, Jesper
name: Snodgrass, Colin
name: Southworth, John
name: Unda-Sanzana, Eduardo
name: von Essen, Carolina
name: Beaulieu, Jean-Phillipe
name: Blackman, Joshua
name: Hill, Kym
Publisher: name: arXiv
Year: 2019
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: 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 $\sim 9$ d. The asteroseismic analysis also provides us source properties including the source angular size ($\sim 27~μ{\rm as}$) and distance ($\sim 11.5$ 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 $χ^2$ 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 $\sim 0.045~M_{\odot}$ brown dwarf at distance $\sim 9.0$ kpc, or a $\sim 0.073~M_{\odot}$ ultracool dwarf at distance $\sim 9.8$ kpc. Combining the estimated lens properties with a Bayesian analysis using a Galactic model, we find a $\sim 35$ per cent probability for the lens to be a bulge object and $\sim 65$ per cent to be a background disc object.
description: 18 pages, 4 figures, 5 tables. Revised to match version published in MNRAS