Surveys have shown that super-Earth and Neptune-mass exoplanets are more frequent than gas giants around low-mass stars, as predicted by the core accretion theory of planet formation. We report the discovery of a giant planet around the very-low-mass star GJ 3512, as determined by optical and near-infrared radial-velocity observations. The planet has a minimum mass of 0.46 Jupiter masses, very high for such a small host star, and an eccentric 204-day orbit. Dynamical models show that the high eccentricity is most likely due to planet-planet interactions. We use simulations to demonstrate that the GJ 3512 planetary system challenges generally accepted formation theories, and that it puts constraints on the planet accretion and migration rates. Disk instabilities may be more efficient in forming planets than previously thought.
The CARMENES instrument has been operational at the 3.5 m telescope of Calar Alto Observatory since January 2016. It consists of two cross-dispersedéchelle spectrographs covering the wavelength range from 0.52 to 1.71 µm. CARMENES is currently conducting a radial-velocity survey of more than 300 M dwarfs, with a sensitivity sufficient to detect terrestrial planets in their habitable zones. This survey has already yielded a comprehensive spectral atlas of 324 M dwarfs, and it is providing a wealth of diagnostic information on activity in cool stars. The CARMENES Survey data have confirmed a number of known M star planets, and revealed previously unknown planets of GJ 15 A, GJ 1148, and GJ 617 A. CARMENES data have also been used to determine the mass of the transiting planet K2-18 b, and to measure atomic and molecular absorption in planetary atmospheres through transit spectroscopy.
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