TOI-674b: An oasis in the desert of exo-Neptunes transiting a nearby M dwarf

MURGAS, F.; ASTUDILLO-DEFRU, N.; BONFILS, X.; CROSSFIELD, I.; ALMENARA, J.M.; LIVINGSTON, J.; STASSUN, K.G.; KORTH, J.; ORELL-MIQUEL, J.; MORELLO, G.; EASTMAN, J.D.; LISSAUER, J.J.; KANE, S.R.; MORALES, F.Y.; WERNER, M.W.; GORJIAN, V.; BENNEKE, B.; DRAGOMIR, D.; MATTHEWS, E.C.; HOWELL, S.B.; CIARDI, D.; GONZALES, E.; MATSON, R.; BEICHMAN, C.; SCHLIEDER, J.; COLLINS, K.A.; COLLINS, K.I.; JENSEN, E.L.N.; EVANS, P.; POZUELOS, F.J.; GILLON, M.; JEHIN, E.; BARKAOUI, K.; ARTIGAU, E.; BOUCHY, F.; CHARBONNEAU, D.; DELFOSSE, X.; DÍAZ, R.F.; DOYON, R.; FIGUEIRA, P.; FORVEILLE, T.; LOVIS, C.; MELO, C.; GAISNÉ, G.; PEPE, F.; SANTOS, N.C.; SÉGRANSAN, D.; UDRY, S.; GOEKE, R.F.; LEVINE, A.M.; QUINTANA, E.V.; GUERRERO, N.M.; MIRELES, I.; CALDWELL, D.A.; TENENBAUM, P.; BRASSEUR, C.E.; RICKER, G.; VANDERSPEK, R.; LATHAM, D.W.; SEAGER, S.; WINN, J.; JENKINS, J.M.

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Año: 2021 vol. 653

0004-6361

Context. The NASA mission TESS is currently doing an all-sky survey from space to detect transiting planets around bright stars. As part of the validation process, the most promising planet candidates need to be confirmed and characterized using follow-up observations. Aims. In this article, our aim is to confirm the planetary nature of the transiting planet candidate TOI-674b using spectroscopic and photometric observations. Methods. We use TESS, Spitzer, ground-based light curves, and HARPS spectrograph radial velocity measurements to establish the physical properties of the transiting exoplanet candidate TOI-674b. We perform a joint fit of the light curves and radial velocity time series to measure the mass, radius, and orbital parameters of the candidate. Results. We confirm and characterize TOI-674b, a low-density super-Neptune transiting a nearby M dwarf. The host star (TIC 158588995, V = 14.2 mag, J = 10.3 mag) is characterized by its M2V spectral type with M = 0.420 ± 0.010 M , R = 0.420 ± 0.013 R , and Teff = 3514 ± 57 K; it is located at a distance d = 46.16 ± 0.03 pc. Combining the available transit light curves plus radial velocity measurements and jointly fitting a circular orbit model, we find an orbital period of 1.977143 ± 3 × 10-6 days, a planetary radius of 5.25 ± 0.17 R , and a mass of 23.6 ± 3.3 M implying a mean density of ρp =0.91 ± 0.15 g cm-3. A non-circular orbit model fit delivers similar planetary mass and radius values within the uncertainties. Given the measured planetary radius and mass, TOI-674b is one of the largest and most massive super-Neptune class planets discovered around an M-type star to date. It is found in the Neptunian desert, and is a promising candidate for atmospheric characterization using the James Webb Space Telescope.