Search for Nearby Earth Analogs. III. Detection of ten new planets, three planet candidates, and confirmation of three planets around eleven nearby M dwarfs

TL;DR

This study identifies ten new Earth-sized planet candidates and confirms three previous ones around nearby M dwarfs, highlighting potential targets for habitability studies and future direct imaging efforts.

Contribution

The paper reports the discovery of new Earth analogs, confirms previous candidates, and analyzes planetary system architectures around nearby M dwarfs using radial velocity data.

Findings

Ten strong planet candidates identified

Three previously known candidates confirmed

Detection of five two-planet systems and diverse planet types

Abstract

Earth-sized planets in the habitable zones of M dwarfs are good candidates for the study of habitability and detection of biosignatures. To search for these planets, we analyze all available radial velocity data and apply four signal detection criteria to select the optimal candidates. We find ten strong candidates satisfying these criteria and three weak candidates showing inconsistency over time due to data samplings. We also confirm three previous planet candidates and improve their orbital solutions through combined analyses of updated data sets. Among the strong planet candidates, HIP 38594 b is a temperate super-Earth with a mass of $8.2 \pm 1.7$ $M_\oplus$ and an orbital period of $60.7\pm0.1$ days, orbiting around an early-type M dwarf. Early-type M dwarfs are less active and thus are better hosts for habitable planets than mid-type and late-type M dwarfs. Moreover, we report the detection of five two-planet systems, including two systems made up of a warm or cold Neptune and a cold Jupiter, consistent with a positive correlation between these two types of planets. We also detect three temperate Neptunes, four cold Neptunes, and four cold Jupiters, contributing to a rarely explored planet population. Due to their proximity to the Sun, these planets on wide orbits are appropriate targets for direct imaging by future facilities such as HabEx and ELT.