Guillem Anglada-Escudé, Bárbara Rojas-Ayala, Alan P. Boss, Alicya J. Weinberger, James P. Lloyd
GJ 1214 is orbited by a super-Earth-mass planet that transits in front of it. It is a primary target for the ongoing efforts to understand the emerging population of super-Earth-mass planets around M dwarfs, some of them detected within the habitable zone of their host stars. We present precision astrometric measurements, a re-analysis of HARPS radial velocity measurements, and medium resolution infrared spectroscopy of GJ 1214. We combine these measurements with recent transit measurements and new catalog photometry to provide a comprehensive update of the star-planet properties. The distance is obtained at 1.5% precision using CAPSCam astrometry. The new value increases the distance to the star by 10% and is significantly more precise than the previous measurement. New radial velocity measurements were obtained re-analyzing public HARPS spectra using the HARPS-TERRA software. The Doppler data combined with recent transit observations significantly update the orbital solution (especially the planet's eccentricity). The analysis of the infrared spectrum and photometry confirm that the star is enriched in metals compared to the Sun. Using all this information, combined only with empirical mass--luminosity relations for low mass stars, we derive updated values for the bulk properties of the star--planet system. Our analysis shows that the updated expected value for the planet mean density is 1.6+/-0.6 g cm^{-3}, and that a density comparable to the Earth is now completely ruled out. This study illustrates how the fundamental properties of M dwarfs are of paramount importance in the proper characterization of the low mass planetary candidates orbiting them. Additional Doppler observations, and/or or detection of the secondary transit, are necessary to improve the constraints on the planet properties.
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http://arxiv.org/abs/1210.8087
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