We report the lens mass and distance measurements of the nearby microlensing event TCP J05074264+2447555 (Kojima-1). We measure the microlens parallax vector using Spitzer and ground-based light curves with constraints on the direction of lens-source relative proper motion derived from Very Large Telescope Interferometer (VLTI) GRAVITY observations. Combining this determination with the angular Einstein radius measured by VLTI-GRAVITY observations, we find that the lens is a star with mass at a distance D L = 429 ± 21 pc. We find that the blended light basically all comes from the lens. The lens-source proper motion is , so with currently available adaptive-optics instruments, the lens and source can be resolved in 2021. This is the first microlensing event whose lens mass is unambiguously measured by interferometry + satellite-parallax observations, which opens a new window for mass measurements of isolated objects such as stellar-mass black holes.
CITATION STYLE
Zang, W., Dong, S., Gould, A., Calchi Novati, S., Chen, P., Yang, H., … Zhu, W. (2020). Spitzer + VLTI-GRAVITY Measure the Lens Mass of a Nearby Microlensing Event. The Astrophysical Journal, 897(2), 180. https://doi.org/10.3847/1538-4357/ab9749
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