Kepler-432 b: a massive warm Jupiter in a 52-day eccentric orbit transiting a giant star

Abstract

We study the Kepler object Kepler-432, an evolved star ascending the red giant branch. By deriving precise radial velocities from multi-epoch high-resolution spectra of Kepler-432 taken with the CAFE spectrograph at the 2.2m telescope of Calar Alto Observatory and the FIES spectrograph at the Nordic Optical Telescope of Roque de Los Muchachos Observatory, we confirm the planetary nature of the object Kepler-432 b, which has a transit period of 52 days. We find a planetary mass of Mp=5.84 +\- 0.05 Mjup and a high eccentricity of e=0.478 +\- 0.004. With a semi-major axis of a=0.303 +\- 0.007 AU, Kepler-432 b is the first bona fide warm Jupiter detected to transit a giant star. We also find a radial velocity linear trend of 0.44 +\- 0.04 m s${}^{-1}$ d${}^{-1}$, which suggests the presence of a third object in the system. Current models of planetary evolution in the post-main-sequence phase predict that Kepler-432 b will be most likely engulfed by its host star before the latter reaches the tip of the red giant branch.

5 pages, 3 figures. Accepted for publication in A&A. Updated title and corrected typos. See also paper by Ciceri et al

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Cited by in corpus (10)

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• Moderately Eccentric Warm Jupiters from Secular Interactions with Exterior Companions
• Kepler-447b: a hot-Jupiter with an extremely grazing transit
• TOI-1670 b and c: An Inner Sub-Neptune with an Outer Warm Jupiter Unlikely to have Originated from High-Eccentricity Migration
• The discovery of a planetary candidate around the evolved low-mass Kepler giant star HD 175370
• Discovery of an inflated hot Jupiter around a slightly evolved star TOI-1789
• Fitting Formulae and Constraints for the Existence of S-type and P-type Habitable Zones
• A simple model to describe intrinsic stellar noise for exoplanet detection around red giants
• Companions to Kepler giant stars: A long-period eccentric substellar companion to KIC 3526061 and a stellar companion to HD 187878