A hot sub-Neptune in the desert and a temperate super-Earth around faint M dwarfs

Color validation of TOI-4479b and TOI-2081b

¹ Instituto de Astrofísica de Canarias (IAC), 38200 La Laguna, Tenerife, Spain
e-mail: emma.esparza.borges@iac.es
² Departamento de Astrofísica, Universidad de La Laguna (ULL), 38206 La Laguna, Tenerife, Spain
³ Department for Physics and Astronomy, University of Heidelberg, Germany
⁴ Landesternwarte Königstuhl (LSW), Zentrum für Astronomie der Universität Heidelberg, Königstuhl 12, 69117 Heidelberg, Germany
⁵ Centro de Astrobiologia (CSIC-INTA), Carretera de Ajalvir km 4, 28850 Torrejon de Ardoz, Madrid, Spain
⁶ Leiden Observatory, Leiden University, Postbus 9513, 2300 RA Leiden, The Netherlands
⁷ Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
⁸ Department of Astronomy, University of California Berkeley, Berkeley, CA 94720, USA
⁹ Department of Astronomy, University of Maryland, College Park, College Park, MD 20742 USA
¹⁰ Department of Space, Earth and Environment, Astronomy and Plasma Physics, Chalmers University of Technology, 412 96 Gothenburg, Sweden
¹¹ Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomia s/n, 18008 Granada, Spain
¹² Sternberg Astronomical Institute, Lomonosov Moscow State University, 13 Universitetski prospekt, 119992 Moscow, Russia University, Russia
¹³ Astrobiology Research Unit, Université de Liège, 19C Allée du 6 Août, 4000 Liège, Belgium
¹⁴ Patashnick Voorheesville Observatory, Voorheesville, NY 12186, USA
¹⁵ Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
¹⁶ MIT Kavli Institute for Astrophysics and Space Research, Cambridge, MA 02139, USA
¹⁷ Komaba Institute for Science, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, Japan
¹⁸ Astrobiology Center, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
¹⁹ Department of Astronomy, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
²⁰ National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
²¹ Division of Science, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
²² SETI Institute, Mountain View, CA 94043, USA
²³ NASA Ames Research Center, Moffett Field, CA 94035, USA
²⁴ Department of Multi-Disciplinary Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, Japan
²⁵ Institute of Astronomy and Astrophysics, Academia Sinica, PO Box 23-141, Taipei 10617, Taiwan, R.O.C.
²⁶ Department of Astrophysics, National Taiwan University, Taipei 10617, Taiwan, R.O.C.
²⁷ Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
²⁸ Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
²⁹ Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA

Received: 7 April 2022
Accepted: 17 June 2022

Abstract

Aims. We report the discovery and validation of two TESS exoplanets orbiting faint M dwarfs: TOI-4479b and TOI-2081b.

Methods. We jointly analyzed space (TESS mission) and ground-based (MuSCAT2, MuSCAT3 and SINISTRO instruments) light curves using our multicolor photometry transit analysis pipeline. This allowed us to compute contamination limits for both candidates and validate them as planet-sized companions.

Results. We found TOI-4479b to be a sub-Neptune-sized planet (R_p = 2.82_−0.63^+0.65 R_⊕) and TOI-2081b to be a super-Earth-sized planet (R_p = 2.04_−0.54^+0.50 R_⊕). Furthermore, we obtained that TOI-4479b, with a short orbital period of 1.15890_−0.00001^+0.00002 days, lies within the Neptune desert and is in fact the largest nearly ultra-short period planet around an M dwarf known to date.

Conclusions. These results make TOI-4479b rare among the currently known exoplanet population of M dwarf stars and an especially interesting target for spectroscopic follow-up and future studies of planet formation and evolution.