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

September 2021 • 2021A&A...653A..60M

Authors • 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.

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 T_eff = 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 ρ_p =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.

Links

• PREPRINT http://arxiv.org/abs/2106.01246
• POSTSCRIPT https://www.aanda.org/10.1051/0004-6361/202140718/postscript
• ELECTR https://doi.org/10.1051%2F0004-6361%2F202140718
• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2021A%26A...653A..60M
• PDF https://www.aanda.org/10.1051/0004-6361/202140718/pdf
• DATA http://archive.eso.org/bin/ads2eso?2021A%26A...653A..60M
• DATA https://archive.stsci.edu/mastbibref.php?bibcode=2021A%26A...653A..60M
• DATA https://irsa.ipac.caltech.edu/bibdata/2021/M/2021A&A...653A..60M.html