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Spitzer Microlensing Parallax Reveals Two Isolated Stars in the Galactic Bulge

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Complete Citation

  • Zang, Weicheng, Shvartzvald, Yossi, Wang, Tianshu, Udalski, Andrzej, Lee, Chung-Uk, Sumi, Takahiro, Skottfelt, Jesper, Li, Shun-Sheng, Mao, Shude, Zhu, Wei, Yee, Jennifer C., Calchi Novati, Sebastiano, Beichman, Charles A., Bryden, Geoffery, Carey, Sean, Gaudi, B. Scott, Henderson, Calen B., Spitzer team, Mróz, Przemek, Skowron, Jan, Poleski, Radoslaw, Szymański, Michał K., Soszyński, Igor, Pietrukowicz, Paweł, Kozłowski, Szymon et al. 2020. "Spitzer Microlensing Parallax Reveals Two Isolated Stars in the Galactic Bulge." The Astrophysical Journal, 891 3. https://doi.org/10.3847/1538-4357/ab6ff8.

Overview

Abstract

  • We report the mass and distance measurements of two single-lens events from the 2017 Spitzer 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 Spitzer observations. We find that the lens of OGLE-2017-BLG-1254 is a 0.60 ± 0.03 M star with DLS = 0.53 ± 0.11 kpc, where DLS 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 0.51-0.10 0.12 M_{☉} star with DLS = 0.40 ± 0.12 kpc or a 0.38-0.12 0.13 M_{☉} star with DLS = 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 Spitzer finite-source events with the expectations from a Galactic model, we find that the Spitzer sample is in agreement with the probability of finite-source effects occurring in single-lens events.

Publication Date

  • 2020

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