K2-287b: an Eccentric Warm Saturn transiting a G-dwarf

TL;DR

This paper reports the discovery and characterization of K2-287b, a warm, eccentric Saturn-mass exoplanet orbiting a G-dwarf star, providing insights into planetary migration and structure unaffected by stellar irradiation.

Contribution

The study presents the first detailed characterization of K2-287b, including its mass, radius, orbit, and host star properties, expanding the sample of well-studied warm giant exoplanets.

Findings

K2-287b has a mass of 0.317 M_J and a radius of 0.833 R_J.

The planet's orbit is eccentric with e = 0.476.

The host star is a metal-rich G dwarf with T_eff ≈ 5673 K.

Abstract

We report the discovery of K2-287b, a Saturn mass planet orbiting a G-dwarf with a period of $P \approx 15$ days. First uncovered as a candidate using K2 campaign 15 data, follow-up photometry and spectroscopy were used to determine a mass of $M_P = 0.317 \pm 0.026$ $M_J$, radius $R_P = 0.833 \pm 0.013$ $R_J$, period $P = 14.893291 \pm 0.000025$ days and eccentricity $e = 0.476 \pm 0.026$. The host star is a metal-rich $V=11.410 \pm 0.129$ mag G dwarf for which we estimate a mass $M_* = 1.056$ $M_\odot$, radius $R_* = 1.07 \pm 0.01$ $R_\odot$, metallicity [Fe/H] = $0.20 \pm 0.05$ and $T_{eff} = 5673 \pm 75$ K. This warm eccentric planet with a time-averaged equilibrium temperature of $T_{eq} \approx 800$ K adds to the small sample of giant planets orbiting nearby stars whose structure is not expected to be affected by stellar irradiation. Follow-up studies on the K2-287 system could help in constraining theories of migration of planets in close-in orbits.