OGLE-2017-BLG-1038: A Possible Brown-dwarf Binary Revealed by Spitzer Microlensing Parallax
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 ( ${M}_{1}={170}_{-50}^{+40}{M}_{J}$ and ${M}_{2}={110}_{-30}^{+20}{M}_{J}$ ), or well below ( ${M}_{1}={22.5}_{-0.4}^{+0.7}{M}_{J}$ and ${M}_{2}={13.3}_{-0.3}^{+0.4}{M}_{J}$ ) 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 10 years through infrared adaptive-optics imaging with a 40 m class telescope.
- Publication:
-
The Astronomical Journal
- Pub Date:
- September 2022
- DOI:
- 10.3847/1538-3881/ac7d4c
- arXiv:
- arXiv:2302.07497
- Bibcode:
- 2022AJ....164..102M
- Keywords:
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- Binary lens microlensing;
- Gravitational microlensing;
- Satellite microlensing parallax;
- Brown dwarfs;
- Gaussian Processes regression;
- 2136;
- 672;
- 2148;
- 185;
- 1930;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Earth and Planetary Astrophysics;
- Astrophysics - Instrumentation and Methods for Astrophysics
- E-Print:
- 20 pages, 11 figures, 4 tables