TOI-674b: An oasis in the desert of exo-Neptunes transiting a nearby M dwarf
Bouchy, F.; Korth, J.; Doyon, R.; Ségransan, D.; Bonfils, X.; Collins, K. A.; Collins, K. I.; Gillon, M.; Jenkins, J. M.; Lovis, C.; Santos, N. C.; Seager, S.; Udry, S.; Pepe, F.; Figueira, P.; Gorjian, V.; Jehin, E.; Barkaoui, K.; Almenara, J. M.; Delfosse, X.; Díaz, R. F.; Forveille, T.; Latham, D. W.; Ricker, G.; Vanderspek, R.; Winn, J.; Morello, G.; Brasseur, C. E.; Murgas, F.; Beichman, C.; Orell-Miquel, J.; Gonzales, E.; Kane, S. R.; Stassun, K. G.; Astudillo-Defru, N.; Charbonneau, D.; Jensen, E. L. N.; Quintana, E. V.; Werner, M. W.; Howell, S. B.; Matthews, E. C.; Livingston, J.; Levine, A. M.; Caldwell, D. A.; Tenenbaum, P.; Artigau, E.; Pozuelos, F. J.; Dragomir, D.; Lissauer, J. J.; Benneke, B.; Melo, C.; Crossfield, I.; Eastman, J. D.; Morales, F. Y.; Ciardi, D.; Matson, R.; Schlieder, J.; Evans, P.; Gaisné, G.; Goeke, R. F.; Guerrero, N. M.; Mireles, I.
Spain, Chile, France, United States, Japan, Sweden, Canada, Switzerland, Belgium, Morocco, Argentina, Portugal
Abstract
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.