A HARPS view on K2-3

TL;DR

This study uses HARPS to measure the masses of three super-Earths orbiting the nearby M dwarf K2-3, providing insights into their composition and potential habitability, especially for the outer planet near the habitable zone.

Contribution

First mass measurements of K2-3 planets using HARPS, revealing their likely rocky nature and water content, aiding future habitability assessments.

Findings

Planet b has a mass of 8.4±2.1 M⊕ and is likely rocky.

Planet b's density suggests it could contain up to 50% water.

Mass determinations for planets c and d are affected by stellar activity.

Abstract

K2 space observations recently found that three super-Earths transit the nearby M dwarf K2-3. The apparent brightness and the small physical radius of their host star rank these planets amongst the most favourable for follow-up characterisations. The outer planet orbits close to the inner edge of the habitable zone and might become one of the first exoplanets searched for biomarkers using transmission spectroscopy. We used the HARPS velocimeter to measure the mass of the planets. The mass of planet $b$ is $8.4\pm2.1$ M$_\oplus$, while our determination of those planets $c$ and $d$ are affected by the stellar activity. With a density of $4.32^{+2.0}_{-0.76}$ $\mathrm{g\;cm^{-3}}$, planet $b$ is probably mostly rocky, but it could contain up to 50% water.