Hidden Gems in TESS: sherlock finds two new rocky planets around nearby M dwarfs

TL;DR

The paper reports the discovery of two new rocky exoplanets around nearby M dwarf stars using the Sherlock pipeline on TESS data, confirmed with ground-based telescopes, and discusses their characteristics and potential for future observations.

Contribution

Introduction of Sherlock, a specialized pipeline that detects sub-threshold planet candidates in TESS data, leading to the discovery of two new rocky planets around M dwarfs.

Findings

Discovered two rocky planets: TOI-237 c and TOI-4336 A c.

Both planets are likely super-Earths below the radius valley.

Systems are dynamically stable with no significant eccentricities.

Abstract

The Hidden Gems project searches the TESS data for additional planets transiting low-mass stars in confirmed systems. Our goal is to identify planet candidates that are below the detection threshold set by the SPOC and QLP pipelines using sherlock, a specialized pipeline for robust detection and vetting of transit signals in TESS data. We present the discovery of two inner rocky planets in the TOI-237 and TOI-4336 A systems, confirmed with ground-based photometry from the TRAPPIST, SPECULOOS, ExTrA, and LCO facilities. TOI-237 c has a radius of 1.21 +/- 0.04Re, orbits its mid-M host star every 1.74 days, and is close to a 3:1 mean-motion resonance with TOI-237 b. TOI-4336 A c has a radius of 1.17 +/- 0.06Re, and orbits with a period of 7.58 days an M3.5 host star which is part of a hierarchical triple system. We performed model comparison to search for non-zero eccentricities, and found that the circular transit models are statistically favored. Dynamical simulations show that both systems are in stable configurations, and the TTVs expected for the TOI-237 system are of the order of seconds. TOI-237 c and TOI-4336 A c join the high-interest population of warm likely super-Earths below the so-called "radius valley". In particular, TOI-237 c is a good candidate for phase curve observations with JWST/MIRI thanks to the small radius of the host star and its short period.