A hot sub-Neptune in the desert and a temperate super-Earth around faint M dwarfs: Color validation of TOI-4479b and TOI-2081b

Abstract

We report the discovery and validation of two TESS exoplanets orbiting faint M dwarfs: TOI-4479b and TOI-2081b. We have jointly analyzed space (TESS mission) and ground based (MuSCAT2, MuSCAT3 and SINISTRO instruments) lightcurves using our multi-color photometry transit analysis pipeline. This allowed us to compute contamination limits for both candidates and validate them as planet-sized companions. We found TOI-4479b to be a sub-Neptune-sized planet ($R_p=2.82_{-0.63}^{+0.65}{\mathrm{R}}_{\oplus }$) and TOI-2081b to be a super-Earth-sized planet ($R_p=2.04_{-0.54}^{+0.50}{\mathrm{R}}_{\oplus }$). Furthermore, we obtained that TOI-4479b, with a short orbital period of $1.15890_{-0.00001}^{+0.00002}\mathrm{days}$, lies within the Neptune desert and is in fact the largest nearly ultra-short period planet around an M dwarf known to date. These results make TOI-4479b rare among the currently known exoplanet population around M dwarf stars, and an especially interesting target for spectroscopic follow-up and future studies of planet formation and evolution.

Accepted for publication in Astronomy&Astrophysics

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• Confirmation of an He I evaporating atmosphere around the 650-Myr-old sub-Neptune HD235088 b (TOI-1430 b) with CARMENES
• Hundreds of TESS exoplanets might be larger than we thought
• Validation of up to seven TESS planet candidates through multi-colour transit photometry using MuSCAT2 data
• TOI-1442 b and TOI-2445 b: two potentially rocky ultra-short period planets around M dwarfs
• Multicolour Validation of Two Temperate Mini-Neptunes Around M-dwarf Habitable Zones