TESS discovery of a sub-Neptune orbiting a mid-M dwarf TOI-2136
Triaud, Amaury H. M. J.; Latham, David W.; Howell, Steve B.; Collins, Karen A.; Ricker, George R.; Vanderspek, Roland; Seager, Sara; Winn, Joshua N.; Jenkins, Jon M.; Barkaoui, Khalid; Dransfield, Georgina; Günther, Maximilian N.; Shporer, Avi; Collins, Kevin I.; McCormac, James; Aganze, Christian; Rackham, Benjamin V.; Gillon, Michaël; de Wit, Julien; Delrez, Laetitia; Ducrot, Elsa; Jensen, Eric L. N.; Huang, Chelsea X.; Pozuelos, Francisco J.; Gan, Tianjun; Queloz, Didier; Doyon, René; Giacalone, Steven; Dressing, Courtney D.; Mao, Shude; Demory, Brice-Olivier; Schwarz, Richard P.; Vezie, Michael; Wang, Sharon X.; Henze, Christopher E.; Burgasser, Adam; Artigau, Étienne; Cook, Neil J.; Demangeon, Olivier D. S.; Gnilka, Crystal L.; Fouqué, Pascal; Manset, Nadine; Jehin, Emmanuel; Benkhaldoun, Zouhair; Savel, Arjun B.; Pedersen, Peter P.; Ghachoui, Mourad; Timmermans, Mathilde; Theissen, Christopher A.; Soubkiou, Abderahmane; Cadieux, Charles; Arnold, Luc; Burdanov, Artem; Niraula, Prajwal; Gómez Maqueo Chew, Yilen; Sebastian, Daniel; Schanche, Nicole; Gill, Holden; Thompson, Samantha; Murray, Catriona A.; Lamman, Claire; Chouqar, Jamila; Fan, Jiahao; Garcia, Lionel; Lin, Zitao; Wells, Robert D.
China, Morocco, Portugal, Canada, United States, France, Belgium, Spain, Switzerland, United Kingdom, Mexico, Netherlands, Australia
Abstract
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.