TOI-674b: an oasis in the desert of exo-Neptunes transiting a nearby M dwarf
Creators: name: Murgas, F.
name: Astudillo-Defru, N.
name: Bonfils, X.
name: Crossfield, Ian
name: Almenara, J. M.
name: Livingston, John
name: Stassun, Keivan G.
name: Korth, Judith
name: Orell-Miquel, Jaume
name: Morello, G.
name: Eastman, Jason D.
name: Lissauer, Jack J.
name: Kane, Stephen R.
name: Morales, Farisa Y.
name: Werner, Michael W.
name: Gorjian, Varoujan
name: Benneke, Björn
name: Dragomir, Diana
name: Matthews, Elisabeth C.
name: Howell, Steve B.
name: Ciardi, David
name: Gonzales, Erica
name: Matson, Rachel
name: Beichman, Charles
name: Schlieder, Joshua
name: Collins, Karen A.
name: Collins, Kevin I.
name: Jensen, Eric L. N.
name: Evans, Phil
name: Pozuelos, Francisco J.
name: Gillon, Michaël
name: Jehin, Emmanuël
name: Barkaoui, Khalid
name: Artigau, E.
name: Bouchy, F.
name: Charbonneau, D.
name: Delfosse, X.
name: Díaz, R. F.
name: Doyon, R.
name: Figueira, P.
name: Forveille, T.
name: Lovis, C.
name: Melo, C.
name: Gaisné, G.
name: Pepe, F.
name: Santos, N. C.
name: Ségransan, D.
name: Udry, S.
name: Goeke, Robert F.
name: Levine, Alan M.
name: Quintana, Elisa V.
name: Guerrero, Natalia M.
name: Mireles, Ismael
name: Caldwell, Douglas A.
name: Tenenbaum, Peter
name: Brasseur, C. E.
name: Ricker, G.
name: Vanderspek, R.
name: Latham, David W.
name: Seager, S.
name: Winn, J.
name: Jenkins, Jon M.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: 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. 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 $\mathrm{M}_\star=0.420\pm 0.010$ M$_\odot$, $\mathrm{R}_\star = 0.420\pm 0.013$ R$_\odot$, and $\mathrm{T}_{\mathrm{eff}} = 3514\pm 57$ K, and is located at a distance $d=46.16 \pm 0.03$ pc. Combining the available transit light curves plus radial velocity measurements and jointly fitting a circular orbit model, we find an orbital period of $1.977143 \pm 3\times 10^{-6}$ days, a planetary radius of $5.25 \pm 0.17$ $\mathrm{R}_\oplus$, and a mass of $23.6 \pm 3.3$ $\mathrm{M}_\oplus$ implying a mean density of $ρ_\mathrm{p} = 0.91 \pm 0.15$ [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 also a resident of the so-called Neptunian desert and a promising candidate for atmospheric characterisation using the James Webb Space Telescope.
description: 22 pages, 16 figures. Accepted for publication in A&amp;A