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154128 - Adaptive optics imaging can break the central caustic cusp approach degeneracy in high-magnification microlensing events.pdf (15.56 MB)
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Adaptive optics imaging can break the central caustic cusp approach degeneracy in high-magnification microlensing events

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journal contribution
posted on 2023-05-21, 14:43 authored by Terry, SK, Bennett, DP, Bhattacharya, A, Koshimoto, N, Jean-Philippe BeaulieuJean-Philippe Beaulieu, Joshua BlackmanJoshua Blackman, Bond, IA, Andrew ColeAndrew Cole, Lu, JR, Marquette, JB, Ranc, C, Efstathia Natalia RektsiniEfstathia Natalia Rektsini, Vandorou, A

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 and at a distance of kpc and a projected separation of 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.


Australian Research Council


Publication title

The Astronomical Journal





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School of Natural Sciences


Institute of Physics Publishing, Inc.

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United States

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© 2022. The Authors. Published by the American Astronomical Society. This article is licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0) License (, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

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