TESS discovery of a sub-Neptune orbiting a mid-M dwarf TOI-2136

Tianjun Gan , Abderahmane Soubkiou , Sharon X. Wang , Zouhair Benkhaldoun , Shude Mao , Étienne Artigau , Pascal Fouqué (1, 2) , Luc Arnold (1) , Steven Giacalone , Christopher A. Theissen , Christian Aganze , Adam Burgasser , Karen A. Collins , Avi Shporer , Khalid Barkaoui , Mourad Ghachoui , Steve B. Howell , Claire Lamman , Olivier D. S. Demangeon , Artem Burdanov , Charles Cadieux , Jamila Chouqar , Kevin I. Collins , Neil J. Cook , Laetitia Delrez , Brice-Olivier Demory , René Doyon , Georgina Dransfield , Courtney D. Dressing , Elsa Ducrot , Jiahao Fan , Lionel Garcia , Holden Gill , Michaël Gillon , Crystal L. Gnilka , Yilen Gómez Maqueo Chew , Maximilian N. Günther , Christopher E. Henze , Chelsea X. Huang , Emmanuel Jehin , Eric L. N. Jensen , Zitao Lin , Nadine Manset (1) , James Mccormac , Catriona A. Murray , Prajwal Niraula , Peter P. Pedersen , Francisco J. Pozuelos , Didier Queloz , Benjamin V. Rackham , Arjun B. Savel , Nicole Schanche , Richard P. Schwarz , Daniel Sebastian , Samantha Thompson , Mathilde Timmermans , Amaury H. M. J. Triaud , Michael Vezie , Robert D. Wells , Julien de Wit , George R. Ricker , Roland Vanderspek , David W. Latham , Sara Seager , Joshua N. Winn , Jon M. Jenkins

1 CFHT - Canada-France-Hawaii Telescope Corporation
2 IRAP - Institut de recherche en astrophysique et planétologie

We present the discovery of TOI-2136 b, a sub-Neptune planet transiting a nearby M4.5V-type star every 7.85 d, identified through photometric measurements from the Transiting Exoplanet Survey Satellite (TESS) mission. The host star is located 33 pc away with a radius of R_* = 0.34 ± 0.02 R_⊙, a mass of $0.34\pm 0.02 \, \mathrm{M}_{\odot }$, and an effective temperature of 3342 ± 100 K. We estimate its stellar rotation period to be 75 ± 5 d based on archival long-term photometry. We confirm and characterize the planet based on a series of ground-based multiwavelength photometry, high-angular-resolution imaging observations, and precise radial velocities from Canada-France-Hawaii Telescope (CFHT)/SpectroPolarimètre InfraROUge (SPIRou). Our joint analysis reveals that the planet has a radius of 2.20 ± 0.17 R_⊕ and a mass of 6.4 ± 2.4 M_⊕. The mass and radius of TOI-2136 b are consistent with a broad range of compositions, from water-ice to gas-dominated worlds. TOI-2136 b falls close to the radius valley for M dwarfs predicted by thermally driven atmospheric mass-loss models, making it an interesting target for future studies of its interior structure and atmospheric properties.

Keywords: planets and satellites: detection; stars: individual: TIC 336128819 - TOI-2136; planetary systems; Astrophysics - Earth and Planetary Astrophysics; Astrophysics - Solar and Stellar Astrophysics

Domains: Sciences of the Universe [physics]

Tianjun Gan, Abderahmane Soubkiou, Sharon X. Wang, Zouhair Benkhaldoun, Shude Mao, et al.. TESS discovery of a sub-Neptune orbiting a mid-M dwarf TOI-2136. Monthly Notices of the Royal Astronomical Society, 2022, 514, pp.4120-4139. ⟨10.1093/mnras/stac1448⟩. ⟨insu-03867454⟩