TOI-220 b: A warm sub-Neptune discovered by TESS

HOYER, S.; GANDOLFI, D.; ARMSTRONG, D.J.; DELEUIL, M.; ACUÑA, L.; DE MEDEIROS, J.R.; GOFFO, E.; LILLO-BOX, J.; DELGADO MENA, E.; LOPEZ, T.A.; SANTERNE, A.; SOUSA, S.; FRIDLUND, M.; ADIBEKYAN, V.; COLLINS, K.A.; SERRANO, L.M.; CORTÉS-ZULETA, P.; HOWELL, S.B.; DEEG, H.; AGUICHINE, A.; BARRAGÁN, O.; BRYANT, E.M.; CANTO MARTINS, B.L.; COLLINS, K.I.; COOKE, B.F.; DÍAZ, R.F.; ESPOSITO, M.; FURLAN, E.; HOJJATPANAH, S.; JACKMAN, J.; JENKINS, J.M.; JENSEN, E.L.N.; LATHAM, D.W.; LEÃO, I.C.; MATSON, R.A.; NIELSEN, L.D.; OSBORN, A.; OTEGI, J.F.; RODLER, F.; SABOTTA, S.; SCOTT, N.J.; SEAGER, S.; STOCKDALE, C.; STRØM, P.A.; VANDERSPEK, R.; VAN EYLEN, V.; WHEATLEY, P.J.; WINN, J.N.; ALMENARA, J.M.; BARRADO, D.; BARROS, S.C.C.; BAYLISS, D.; BOUCHY, F.; BOYD, P.T.; CABRERA, J.; COCHRAN, W.D.; DEMANGEON, O.; DOTY, J.P.; DUMUSQUE, X.; FIGUEIRA, P.; FONG, W.; GRZIWA, S.; HATZES, A.P.; KABÁTH, P.; KNUDSTRUP, E.; KORTH, J.; LIVINGSTON, J.H.; LUQUE, R.; MOUSIS, O.; MULLALLY, S.E.; OSBORN, H.P.; PALLÉ, E.; PERSSON, C.M.; REDFIELD, S

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2021 vol. 505 p. 3361 - 3379

0035-8711

In this paper, we report the discovery of TOI-220 b, a new sub-Neptune detected by the Transiting Exoplanet Survey Satellite (TESS) and confirmed by radial velocity follow-up observations with the HARPS spectrograph. Based on the combined analysis of TESS transit photometry and high precision radial velocity measurements, we estimate a planetary mass of 13.8 ± 1.0 M⊕ and radius of 3.03 ± 0.15 R⊕, implying a bulk density of 2.73 ± 0.47 g cm-3. TOI-220 b orbits a relative bright (V= 10.4) and old (10.1 ± 1.4 Gyr) K dwarf star with a period of ∼10.69 d. Thus, TOI-220 b is a new warm sub-Neptune with very precise mass and radius determinations. A Bayesian analysis of the TOI-220 b internal structure indicates that due to the strong irradiation it receives, the low density of this planet could be explained with a steam atmosphere in radiative-convective equilibrium and a supercritical water layer on top of a differentiated interior made of a silicate mantle and a small iron core.