# A super-Earth and two sub-Neptunes transiting the nearby and quiet M dwarf TOI-270

## TL;DR

This paper reports the discovery of three small transiting exoplanets around the nearby M dwarf TOI-270, highlighting their potential for detailed characterization due to their near-resonance, brightness, and quiet stellar environment.

## Contribution

The discovery of a multi-planet system around a nearby bright M dwarf with planets suitable for mass and atmospheric studies is a novel addition to exoplanet research.

## Key findings

- Three small planets transiting TOI-270 with near-resonant periods.
- Planets are suitable for mass and atmospheric characterization.
- System is ideal for studying small, temperate exoplanets.

## Abstract

We report the Transiting Exoplanet Survey Satellite discovery of three small planets transiting one of the nearest and brightest M dwarf hosts to date, TOI-270 (TIC 259377017; K-mag 8.3; 22.5 parsec). The M3V-type star is transited by the super-Earth-sized TOI-270 b (1.247+0.089-0.083 R_earth) and the sub-Neptune-sized exoplanets TOI-270 c (2.42+-0.13 R_earth) and TOI-270 d (2.13+-0.12 R_earth). The planets orbit close to a mean-motion resonant chain, with periods (3.36, 5.66, and 11.38 days) near ratios of small integers (5:3 and 2:1). TOI-270 is a prime target for future studies since: 1) its near-resonance allows detecting transit timing variations for precise mass measurements and dynamical studies; 2) its brightness enables independent radial velocity mass measurements; 3) the outer planets are ideal for atmospheric characterisation via transmission spectroscopy; and 4) the quiet star enables future searches for habitable zone planets. Altogether, very few systems with small, temperate exoplanets are as suitable for such complementary and detailed characterisation as TOI-270.