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MOA-2011-BLG-293Lb: First Microlensing Planet Possibly in the Habitable Zone

Abstract : We used Keck adaptive optics observations to identify the first planet discovered by microlensing to lie in or near the habitable zone, i.e., at projected separation r = 1.1 ± 0.1 AU from its ML = 0.86 ± 0.06 M host, being the highest microlensing mass definitely identified. The planet has a mass mp = 4.8 ± 0.3 M Jup, and could in principle have habitable moons. This is also the first planet to be identified as being in the Galactic bulge with good confidence: DL = 7.72 ± 0.44 kpc. The planet/host masses and distance were previously not known, but only estimated using Bayesian priors based on a Galactic model. These estimates had suggested that the planet might be a super-Jupiter orbiting an M dwarf, a very rare class of planets. We obtained high-resolution JHK images using Keck adaptive optics to detect the lens and so test this hypothesis. We clearly detect light from a G dwarf at the position of the event, and exclude all interpretations other than that this is the lens with high confidence (95%), using a new astrometric technique. The calibrated magnitude of the planet host star is HL = 19.16 ± 0.13. We infer the following probabilities for the three possible orbital configurations of the gas giant planet: 53% to be in the habitable zone, 35% to be near the habitable zone, and 12% to be beyond the snow line, depending on the atmospherical conditions and the uncertainties on the semimajor axis.
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Submitted on : Tuesday, April 19, 2022 - 4:18:00 PM
Last modification on : Wednesday, April 20, 2022 - 3:40:09 AM

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V. Batista, J. -P. Beaulieu, A. Gould, D. P. Bennett, J. C. Yee, et al.. MOA-2011-BLG-293Lb: First Microlensing Planet Possibly in the Habitable Zone. The Astrophysical Journal, 2014, 780, ⟨10.1088/0004-637X/780/1/54⟩. ⟨insu-03645759⟩

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