Spitzer Microlensing Parallax Reveals Two Isolated Stars in the Galactic Bulge

Weicheng Zang, Yossi Shvartzvald, Tianshu Wang, Andrzej Udalski, Chung-Uk Lee, Takahiro Sumi, Jesper Skottfelt, Shun-Sheng Li, Shude Mao, Wei Zhu, Jennifer C. Yee, Sebastiano Calchi Novati, Charles A. Beichman, Geoffery Bryden, Sean Carey, B. Scott Gaudi, Calen B. Henderson, Przemek Mróz, Jan Skowron, Radoslaw Poleski, Michał K. Szymański, Igor Soszyński, Paweł Pietrukowicz, Szymon Kozłowski, Krzysztof Ulaczyk, Krzysztof A. Rybicki, Patryk Iwanek, Etienne Bachelet, Grant Christie, Jonathan Green, Steve Hennerley, Dan Maoz, Tim Natusch, Richard W. Pogge, Rachel A. Street, Yiannis Tsapras, Michael D. Albrow, Sun-Ju Chung, Andrew Gould, Cheongho Han, Kyu-Ha Hwang, Youn Kil Jung, Yoon-Hyun Ryu, In-Gu Shin, Sang-Mok Cha, Dong-Jin Kim, Hyoun-Woo Kim, Seung-Lee Kim, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Ian A. Bond, Fumio Abe, Richard Barry, David P. Bennett, Aparna Bhattacharya, Martin Donachie, Akihiko Fukui, Yuki Hirao, Yoshitaka Itow, Iona Kondo, Naoki Koshimoto, Man Cheung Alex Li, Yutaka Matsubara, Yasushi Muraki, Shota Miyazaki, Masayuki Nagakane, Clément Ranc, Nicholas J. Rattenbury, Haruno Suematsu, Denis J. Sullivan, Daisuke Suzuki, Paul J. Tristram, Atsunori Yonehara, Martin Dominik, Markus Hundertmark, Uffe G. Jørgensen, Sohrab Rahvar, Sedighe Sajadian, Colin Snodgrass, Valerio Bozza, Martin J. Burgdorf, Daniel F. Evans, R. Figuera Jaimes, Yuri I. Fujii, Luigi Mancini, Penelope Longa-Peña, Christiane Helling, Nuno Peixinho, Markus Rabus, John Southworth, Eduardo Unda-Sanzana, Carolina von Essen

doi:10.48550/arxiv.1904.11204

<jats:title>Abstract</jats:title> <jats:p>We report the mass and distance measurements of two single-lens events from the 2017 <jats:italic>Spitzer</jats:italic> microlensing campaign. The ground-based observations yield the detection of finite-source effects, and the microlens parallaxes are derived from the joint analysis of ground-based observations and <jats:italic>Spitzer</jats:italic> observations. We find that the lens of OGLE-2017-BLG-1254 is a 0.60 ± 0.03 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> star with <jats:italic>D</jats:italic> <jats:sub>LS</jats:sub> = 0.53 ± 0.11 kpc, where <jats:italic>D</jats:italic> <jats:sub>LS</jats:sub> is the distance between the lens and the source. The second event, OGLE-2017-BLG-1161, is subject to the known satellite parallax degeneracy, and thus is either a <jats:inline-formula> <jats:tex-math> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjab6ff8ieqn1.gif" xlink:type="simple"/> </jats:inline-formula> star with <jats:italic>D</jats:italic> <jats:sub>LS</jats:sub> = 0.40 ± 0.12 kpc or a <jats:inline-formula> <jats:tex-math> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjab6ff8ieqn2.gif" xlink:type="simple"/> </jats:inline-formula> star with <jats:italic>D</jats:italic> <jats:sub>LS</jats:sub> = 0.53 ± 0.19 kpc. Both of the lenses are therefore isolated stars in the Galactic bulge. By comparing the mass and distance distributions of the eight published <jats:italic>Spitzer</jats:italic> finite-source events with the expectations from a Galactic model, we find that the <jats:italic>Spitzer</jats:italic> sample is in agreement with the probability of finite-source effects occurring in single-lens events.</jats:p>

Spitzer Microlensing Parallax Reveals Two Isolated Stars in the Galactic Bulge

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