K2-265 b: A Transiting Rocky Super-Earth

TL;DR

This paper reports the discovery and characterization of K2-265 b, a rocky super-Earth with an Earth-like composition, orbiting a bright star with a short period, providing insights into its formation and evolution.

Contribution

The study presents the first detailed mass, radius, and composition analysis of K2-265 b, a super-Earth below the photoevaporation gap, using combined photometry and radial velocity data.

Findings

K2-265 b has a radius of 1.71 R_earth and a mass of 6.54 M_earth.

The planet has a bulk density of 7.1 g/cm^3, indicating a rocky composition.

It likely formed as an exposed rocky core due to photoevaporation.

Abstract

We report the discovery of the super-Earth K2-265 b detected with K2 photometry. The planet orbits a bright (V_mag = 11.1) star of spectral type G8V with a period of 2.37 days. We obtained high-precision follow-up radial velocity measurements from HARPS, and the joint Bayesian analysis showed that K2-265 b has a radius of 1.71 +/- 0.11 R_earth and a mass of 6.54 +/- 0.84 M_earth, corresponding to a bulk density of 7.1 +/- 1.8 g/cm^3 . Composition analysis of the planet reveals an Earth-like, rocky interior, with a rock mass fraction of 80%. The short orbital period and small radius of the planet puts it below the lower limit of the photoevaporation gap, where the envelope of the planet could have eroded due to strong stellar irradiation, leaving behind an exposed core. Knowledge of the planet core composition allows us to infer the possible formation and evolution mechanism responsible for its current physical parameters.