Adaptive Optics Imaging Can Break the Central Caustic Cusp Approach Degeneracy in High-magnification Microlensing Events
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Date
2022-11-01
Open Access Location
Journal Title
Journal ISSN
Volume Title
Publisher
IOP Publishing on behalf of the American Astronomical Society
Rights
CC BY 4.0
Abstract
We report new results for the gravitational microlensing target OGLE-2011-BLG-0950 from adaptive optics images using the Keck Observatory. The original analysis by Choi et al. and reanalysis by Suzuki et al. report degenerate solutions between planetary and stellar binary lens systems. This particular case is the most important type of degeneracy for exoplanet demographics because the distinction between a planetary mass or stellar binary companion has direct consequences for microlensing exoplanet statistics. The 8 and 10 yr baselines allow us to directly measure a relative proper motion of 4.20 ± 0.21 mas yr−1, confirming the detection of the lens star system and ruling out the planetary companion models that predict a ∼4× smaller relative proper motion. The Keck data also rule out the wide stellar binary solution unless one of the components is a stellar remnant. The combination of the lens brightness and close stellar binary light-curve parameters yields primary and secondary star masses of M A = 1.12 − 0.09 + 0.11 and M B = 0.47 − 0.10 + 0.13 M ☉ at a distance of D L = 6.70 − 0.30 + 0.55 kpc and a projected separation of 0.39 − 0.04 + 0.05 au. Assuming that the predicted proper motions are measurably different, the high-resolution imaging method described here can be used to disentangle this degeneracy for events observed by the Roman exoplanet microlensing survey using Roman images taken near the beginning or end of the survey.
Description
Keywords
Gravitational microlensing (672), Binary lens microlensing (2136), Highresolution microlensing event imaging (2138), Binary stars (154), Galactic bulge (2041)
Citation
Terry SK, Bennett DP, Bhattacharya A, Koshimoto N, Beaulieu JP, Blackman JW, Bond IA, Cole AA, Lu JR, Marquette JB, Ranc C, Rektsini N, Vandorou A. (2022). Adaptive Optics Imaging Can Break the Central Caustic Cusp Approach Degeneracy in High-magnification Microlensing Events. Astronomical Journal. 164. 5.