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

T. Gan, A. Soubkiou, S. X. Wang, Z. Benkhaldoun, S. Mao, E. Artigau, P. Fouqué, L. Arnold, S. Giacalone, C. A. Theissen, C. Aganze, A. Burgasser, K. A. Collins, A. Shporer, K. Barkaoui, M. Ghachoui, S. B. Howell, C. Lamman, O. Demangeon, A. Burdanov, C. Cadieux, J. Chouqar, K. I. Collins, N. J. Cook, L. Delrez, B.-O. Demory, R. Doyon, G. Dransfield, C. D. Dressing, E. Ducrot, J. Fan, L. J. Garcia, H. Gill, M. Gillon, C. L. Gnilka, Y. Gómez Maqueo Chew, M. N. Günther, C. E. Henze, C. X. Huang, E. Jehin, E. L. N. Jensen, Z. Lin, N. Manset, J. McCormac, C. A. Murray, P. Niraula, P. P. Pedersen, F. J. Pozuelos, D. Queloz, B. V. Rackham, A. B. Savel, N. Schanche, R. P. Schwarz, D. Sebastian, S. Thompson, M. Timmermans, A. H. M. J. Triaud, M. Vezie, R. D. Wells, J. De Wit, G. R. Ricker, R. K. Vanderspek, D. W. Latham, S. Seager, J. N. Winn, J. M. Jenkins

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±0.02M⁠, 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.

planets and satellites: detection, stars: individual: TIC 336128819 – TOI-2136, planetary systems

Monthly Notices of the Royal Astronomical Society
Volume 514, Issue 3, Page 4120
2022 August

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Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia