Spitzer Microlensing parallax reveals two isolated stars in the Galactic bulge

the MiNDSTEp Collaboration

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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 0:600:03M star with DLS = 0:530:11 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+0:12 􀀀0:10M star with DLS = 0:40 0:12 kpc or a 0:38+0:13 􀀀0:12M star with DLS = 0:530:19 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
occurrence in single lens events.
Original languageEnglish
JournalAstrophysical Journal
Issue number1
Publication statusPublished - 27 Feb 2020


  • astro-ph.SR


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