Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Amber Malpas
Michael D. Albrow
Jennifer C. Yee
Andrew Gould
Andrzej Udalski
Antonio Herrera Martin
Spitzer Team
Charles A. Beichman
Geoffery Bryden
Sebastiano Calchi Novati
Sean Carey
Calen B. Henderson
B. Scott Gaudi
Yossi Shvartzvald
Wei Zhu
KMTNet Collaboration
Sang-Mok Cha
Sun-Ju Chung
Cheongho Han
Kyu-Ha Hwang
Abstract： We report the analysis of microlensing event OGLE-2017-BLG-1038, observed by the Optical Gravitational Lensing Experiment, Korean Microlensing Telescope Network, and Spitzer telescopes. The event is caused by a giant source star in the Galactic Bulge passing over a large resonant binary lens caustic. The availability of space-based data allows the full set of physical parameters to be calculated. However, there exists an eightfold degeneracy in the parallax measurement. The four best solutions correspond to very-low-mass binaries near ($M_1 = 170^{+40}_{-50} M_J$ and $M_2 = 110^{+20}_{-30} M_J$), or well below ($M_1 = 22.5^{+0.7}_{-0.4} M_J$ and $M_2 = 13.3^{+0.4}_{-0.3} M_J$) the boundary between stars and brown dwarfs. A conventional analysis, with scaled uncertainties for Spitzer data, implies a very-low-mass brown dwarf binary lens at a distance of 2 kpc. Compensating for systematic Spitzer errors using a Gaussian process model suggests that a higher mass M-dwarf binary at 6 kpc is equally likely. A Bayesian comparison based on a galactic model favors the larger-mass solutions. We demonstrate how this degeneracy can be resolved within the next ten years through infrared adaptive-optics imaging with a 40 m class telescope.
Peer Review Status:
Awaiting Review
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