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

TL;DR

This paper confirms Kepler-432 b as a dense, massive exoplanet orbiting a red giant star with high eccentricity, using combined radial velocity and photometric data, contributing to understanding planetary system evolution.

Contribution

It provides the first precise mass and eccentricity measurements of Kepler-432 b through high-precision radial velocities and combined photometry, revealing its dense nature and orbital characteristics.

Findings

Kepler-432 b has a mass of approximately 4.87 MJup.

The planet's orbit is highly eccentric with e ≈ 0.535.

Kepler-432 b orbits a red giant star on a 52.5-day period.

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 Mp = 4.87 +/- 0.48 MJup and radius of Rp = 1.120 +/- 0.036 RJup. 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 NIR 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.