Precise mass and radius of a transiting super-Earth planet orbiting the M dwarf TOI-1235: a planet in the radius gap?

Bluhm, P. and Luque, R. and Espinoza, N. and Palle, E. and Caballero, J.A. and Dreizler, S. and Livingston, J.H. and Mathur, S. and Quirrenbach, A. and Stock, S. and Van Eylen, V. and Nowak, G. and López, E.D. and Csizmadia, Sz. and Zapatero Osorio, M.R. and Schöfer, P. and Lillo-Box, J. and Oshagh, M. and Gonzalez-Alvarez, E. and Amado, P.J. and Barrado, D. and Béjar, V.J.S. and Cale, B. and Chaturvedi, P. and Cifuentes, C. and Cochran, W.D. and Collins, K.A. and Collins, K.I. and Cortés-Contreras, M. and Diez Alonso, E. and El Mufti, M. and Ercolino, A. and Fridlund, M. and Gaidos, E. and Garcia, R.A. and Georgieva, I. and González-Cuesta, L. and Guerra, P. and Hatzes, A.P. and Henning, Th. and Herrero, E. and Hidalgo, D. and Isopi, G. and Jeffers, S.V. and Jenkins, J.M. and Jensen, E.L.N. and Kabath, P. and Kaminski, A. and Kemmer, J. and Korth, J. and Kossakowski, D. and Kurster, M. and Lafarga, M. and Mallia, F. and Montes, D. and Morales, J.C. and Morales-Calderón, M. and Murgas, F. and Narita, N. and Passegger, V.M. and Pedraz, S. and Persson, C.M. and Plavchan, P. and Rauer, H. and Redfield, S. and Reffert, S. and Reiners, A. and Ribas, I. and Ricker, G.R. and Rodriguez-López, C. and Santos, A.R.G. and Seager, S. and Schlecker, M. and Schweitzer, A. and Shan, Y. and Soto, M.G. and Subjak, J. and Tal-Or, L. and Trifonov, T. and Vanaverbeke, S. and Vanderspek, R. and Wittrock, J. and Zechmeister, M. and Zohrabi, F. (2020) Precise mass and radius of a transiting super-Earth planet orbiting the M dwarf TOI-1235: a planet in the radius gap? Astronomy & Astrophysics, 639, A132. EDP Sciences. doi: 10.1051/0004-6361/202038160. ISSN 0004-6361.

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Official URL: https://www.aanda.org/articles/aa/abs/2020/07/aa38160-20/aa38160-20.html

Abstract

We report the confirmation of a transiting planet around the bright weakly active M0.5 V star TOI-1235 (TYC 4384-1735-1, V ≈ 11.5 mag), whose transit signal was detected in the photometric time series of sectors 14, 20, and 21 of the TESS space mission. We confirm the planetary nature of the transit signal, which has a period of 3.44 d, by using precise RV measurements with the CARMENES, HARPS-N, and iSHELL spectrographs, supplemented by high-resolution imaging and ground-based photometry. A comparison of the properties derived for TOI-1235 b with theoretical models reveals that the planet has a rocky composition, with a bulk density slightly higher than that of Earth. In particular, we measure a mass of Mp = 5.9 ± 0.6 M⊕ and a radius of Rp = 1.69 ± 0.08 R⊕, which together result in a density of ρp = 6.7- 1.1+ 1.3 g cm-3. When compared with other well-characterized exoplanetary systems, the particular combination of planetary radius and mass places our discovery in the radius gap, which is a transition region between rocky planets and planets with significant atmospheric envelopes. A few examples of planets occupying the radius gap are known to date. While the exact location of the radius gap for M dwarfs is still a matter of debate, our results constrain it to be located at around 1.7 R⊕ or larger at the insolation levels received by TOI-1235 b (~60 S⊕). This makes it an extremely interesting object for further studies of planet formation and atmospheric evolution.

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