TOI 122b and TOI 237b, two small warm planets orbiting inactive M dwarfs, found by \textit{TESS}

Abstract

We report the discovery and validation of TOI 122b and TOI 237b, two warm planets transiting inactive M dwarfs observed by \textit{TESS}. Our analysis shows TOI 122b has a radius of 2.72$\pm$0.18 R$_\rm{e}$ and receives 8.8$\pm$1.0$\times$ Earth's bolometric insolation, and TOI 237b has a radius of 1.44$\pm$0.12 R$_\rm{e}$ and receives 3.7$\pm$0.5$\times$ Earth insolation, straddling the 6.7$\times$ Earth insolation that Mercury receives from the sun. This makes these two of the cooler planets yet discovered by \textit{TESS}, even on their 5.08-day and 5.43-day orbits. Together, they span the small-planet radius valley, providing useful laboratories for exploring volatile evolution around M dwarfs. Their relatively nearby distances (62.23$\pm$0.21 pc and 38.11$\pm$0.23 pc, respectively) make them potentially feasible targets for future radial velocity follow-up and atmospheric characterization, although such observations may require substantial investments of time on large telescopes.

21 pages, 9 figures, 4 tables, accepted to AJ