Characterization of Low Mass K2 Planet Hosts Using Near-Infrared Spectroscopy

TL;DR

This study uses near-infrared spectroscopy to characterize M dwarf stars hosting K2 exoplanet candidates, deriving stellar and planetary properties to identify potentially rocky planets, though likely none are habitable.

Contribution

First comprehensive near-infrared spectral analysis of K2 M dwarf hosts, linking stellar properties to exoplanet characterization and habitability assessment.

Findings

Identified 35 M dwarf hosts from 56 candidates.

Derived stellar parameters for the M dwarf sample.

Characterized 33 exoplanet candidates, including potential rocky planets.

Abstract

We present moderate resolution near-infrared spectra in $H, J$ and $K$ band of M dwarf hosts to candidate transiting exoplanets discovered by NASA's K2 mission. We employ known empirical relationships between spectral features and physical stellar properties to measure the effective temperature, radius, metallicity, and luminosity of our sample. Out of an initial sample of 56 late-type stars in K2, we identify 35 objects as M dwarfs. For that sub-sample, we derive temperatures ranging from $2,870$ to $4,187$ K, radii of $0.09-0.83$ $R_{\odot}$, luminosities of $-2.67<log L/L_{\odot}<-0.67$ and [Fe/H] metallicities between $-0.49$ and $0.83$ dex. We then employ the stellar properties derived from spectra, in tandem with the K2 lightcurves, to characterize their planets. We report 33 exoplanet candidates with orbital periods ranging from 0.19 to 21.16 days, and median radii and equilibrium temperatures of 2.3 $R_{\oplus}$ and 986 K, respectively. Using planet mass-radius relationships from the literature, we identify 7 exoplanets as potentially rocky, although we conclude that probably none reside in the habitable zone of their parent stars.