Kepler-432 b: a massive planet in a highly eccentric orbit transiting a red giant ^⋆

¹ Max Planck Institute for Astronomy, Königstuhl 17, 69117, Heidelberg, Germany
e-mail: ciceri@mpia.de
² Departamento de Astrofísica, Centro de Astrobiología (CSIC-INTA), 28691 Villanueva de la Cañada, Madrid, Spain
³ Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK

Received: 10 October 2014
Accepted: 28 November 2014

Abstract

We report the first disclosure of the planetary nature of Kepler-432 b (aka Kepler object of interest KOI-1299.01). We accurately constrained its mass and eccentricity by high-precision radial velocity measurements obtained with the CAFE spectrograph at the CAHA 2.2-m telescope. By simultaneously fitting these new data and Kepler photometry, we found that Kepler-432 b is a dense transiting exoplanet with a mass of M_p = 4.87 ± 0.48M_Jup and radius of R_p = 1.120 ± 0.036R_Jup. The planet revolves every 52.5 d around a K giant star that ascends the red giant branch, and it moves on a highly eccentric orbit with e = 0.535 ± 0.030. By analysing two near-IR high-resolution images, we found that a star is located at 1.1′′ from Kepler-432, but it is too faint to cause significant effects on the transit depth. Together with Kepler-56 and Kepler-91, Kepler-432 occupies an almost-desert region of parameter space, which is important for constraining the evolutionary processes of planetary systems.