TOI-1201 b: A mini-Neptune transiting a bright and moderately young M dwarf
Creators: name: Kossakowski, D.
name: Kemmer, J.
name: Bluhm, P.
name: Stock, S.
name: Caballero, J. A.
name: Béjar, V. J. S.
name: Guillén, C. Cardona
name: Lodieu, N.
name: Collins, K. A.
name: Oshagh, M.
name: Schlecker, M.
name: Espinoza, N.
name: Pallé, E.
name: Henning, Th.
name: Kreidberg, L.
name: Kürster, M.
name: Amado, P. J.
name: Anderson, D. R.
name: Morales, J. C.
name: Conti, D.
name: Galadi-Enriquez, D.
name: Guerra, P.
name: Cartwright, S.
name: Charbonneau, D.
name: Chaturvedi, P.
name: Cifuentes, C.
name: Contreras, M. Cortes
name: Dreizler, S.
name: Hellier, C.
name: Henze, C.
name: Herrero, E.
name: Jeffers, S. V.
name: Jenkins, J. M.
name: Jensen, E. L. N.
name: Kaminski, A.
name: Kielkopf, J. F.
name: Kunimoto, M.
name: Lafarga, M.
name: Latham, D. W.
name: Lillo-Box, J.
name: Luque, R.
name: Molaverdikhani, K.
name: Montes, D.
name: Morello, G.
name: Morgan, E. H.
name: Nowak, G.
name: Pavlov, A.
name: Perger, M.
name: Quintana, E. V.
name: Quirrenbach, A.
name: Reffert, S.
name: Reiners, A.
name: Ricker, G.
name: Ribas, I.
name: Lopez, C. Rodriguez
name: Osorio, M. R. Zapatero
name: Seager, S.
name: Schoefer, P.
name: Schweitzer, A.
name: Trifonov, T.
name: Vanaverbeke, S.
name: Vanderspek, R.
name: West, R.
name: Winn, J.
name: Zechmeister, M.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We present the discovery of a transiting mini-Neptune around TOI-1201, a relatively bright and moderately young early M dwarf ($J \approx$ 9.5 mag, $\sim$600-800 Myr) in an equal-mass $\sim$8 arcsecond-wide binary system, using data from the Transiting Exoplanet Survey Satellite (TESS), along with follow-up transit observations. With an orbital period of 2.49 d, TOI-1201 b is a warm mini-Neptune with a radius of $R_\mathrm{b} = 2.415\pm0.090 R_\oplus$. This signal is also present in the precise radial velocity measurements from CARMENES, confirming the existence of the planet and providing a planetary mass of $M_\mathrm{b} = 6.28\pm0.88 M_\oplus$ and, thus, an estimated bulk density of $2.45^{+0.48}_{-0.42}$ g cm$^{-3}$. The spectroscopic observations additionally show evidence of a signal with a period of 19 d and a long periodic variation of undetermined origin. In combination with ground-based photometric monitoring from WASP-South and ASAS-SN, we attribute the 19 d signal to the stellar rotation period ($P_{rot}=$ 19-23 d), although we cannot rule out that the variation seen in photometry belongs to the visually close binary companion. We calculate precise stellar parameters for both TOI-1201 and its companion. The transiting planet is an excellent target for atmosphere characterization (the transmission spectroscopy metric is $97^{+21}_{-16}$) with the upcoming James Webb Space Telescope. It is also feasible to measure its spin-orbit alignment via the Rossiter-McLaughlin effect using current state-of-the-art spectrographs with submeter per second radial velocity precision.
description: 33 pages; 18 figures; accepted for publication in A&amp;A