Two Hot Jupiters from K2 Campaign 4

TL;DR

This paper confirms two hot Jupiters from K2 Campaign 4 using radial velocity measurements, providing detailed planetary and stellar parameters, and highlighting their orbital characteristics and host star properties.

Contribution

The study provides the first confirmation and detailed characterization of two hot Jupiters discovered by K2, including their masses, radii, and host star properties, using multiple spectroscopic instruments.

Findings

K2-29 b has a slightly eccentric orbit with a period of 3.26 days.

K2-30 b orbits a low-metallicity G6V star with a period of 4.10 days.

Both planets have radii close to Jupiter's and masses around half of Jupiter's.

Abstract

We confirm the planetary nature of two transiting hot Jupiters discovered by the Kepler spacecraft's K2 extended mission in its Campaign 4, using precise radial velocity measurements from FIES@NOT, HARPS-N@TNG, and the coud\'e spectrograph on the McDonald Observatory 2.7 m telescope. K2-29 b (EPIC 211089792 b) transits a K1V star with a period of $3.2589263\pm0.0000015$ days; its orbit is slightly eccentric ($e=0.084_{-0.023}^{+0.032}$). It has a radius of $R_P=1.000_{-0.067}^{+0.071}$ $R_J$ and a mass of $M_P=0.613_{-0.026}^{+0.027}$ $M_J$. Its host star exhibits significant rotational variability, and we measure a rotation period of $P_{\mathrm{rot}}=10.777 \pm 0.031$ days. K2-30 b (EPIC 210957318 b) transits a G6V star with a period of $4.098503\pm0.000011$ days. It has a radius of $R_P=1.039_{-0.051}^{+0.050}$ $R_J$ and a mass of $M_P=0.579_{-0.027}^{+0.028}$ $M_J$. The star has a low metallicity for a hot Jupiter host, $[\mathrm{Fe}/\mathrm{H}]=-0.15 \pm 0.05$.