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

V. Batista; J. -P. Beaulieu; A. Gould; D. P. Bennett; J. C Yee; A. Fukui; B. S. Gaudi; T. Sumi; A. Udalski

doi:10.1088/0004-637X/780/1/54

paper

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

arXiv:1310.3706 · doi:10.1088/0004-637X/780/1/54

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 $r_{⊥} = 1.1 \pm 0.1$ AU from its $M_{L} = 0.86 \pm 0.06 M_{⊙}$ host, being the highest microlensing mass definitely identified. The planet has a mass $m_{p} = 4.8 \pm 0.3 M_{Jup}$ , 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: $D_{L} = 7.72 \pm 0.44$ kpc. The planet/host masses and distance were previously not known, but only estimated using Bayesian priors based on a Galactic model (Yee et al. 2012). 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 $J H K$ 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 $H_{L} = 19.16 \pm 0.13$ . 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.

Accepted by ApJ, 21 pages, 4 figures

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

Abstract

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