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.
Bibliographical reference

Astronomy and Astrophysics

Advertised on:
9
2021
Number of authors
62
IAC number of authors
3
Citations
25
Refereed citations
23
Description
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.

Based on observations made with the HARPS instrument on the ESO 3.6 m telescope at La Silla Observatory under program ID 1102.C-0339.
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