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- 19. januar 2018 kl. 03:54 #315842
- Super Nova
We report the discovery of a sub-Jupiter mass planet orbiting beyond the snow line of an M-dwarf most likely in the Galactic disk as part of the joint Spitzer and ground-based monitoring of microlensing planetary anomalies toward the Galactic bulge. The microlensing parameters are strongly constrained by the light curve modeling and in particular by the Spitzer-based measurement of the microlens parallax, πE. However, in contrast to many planetary microlensing events, there are no caustic crossings, so the angular Einstein radius, θE has only an upper limit based on the light curve modeling alone. Additionally, the analysis leads us to identify 8 degenerate configurations: the four-fold microlensing parallax degeneracy being doubled by a degeneracy in the caustic structure present at the level of the ground-based solutions. To pinpoint the physical parameters, and at the same time to break the parallax degeneracy, we make use of a series of arguments: the χ2 hierarchy, the Rich argument, and a prior Galactic model. The preferred configuration is for a host at DL=3.73-0.67+0.66 kpc with mass ML=0.30-0.12+0.15 M⊙, orbited by a Saturn-like planet with Mplanet=0.43-0.17+0.21 MJup at projected separation a⊥=1.70-0.39+0.38 au, about 2.1 times beyond the system snow line. Therefore, it adds to the growing population of sub-Jupiter planets orbiting near or beyond the snow line of M-dwarfs discovered by microlensing. Based on the rules of the real-time protocol for the selection of events to be followed up with Spitzer, this planet will not enter the sample for measuring the Galactic distribution of planets.
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