TOI-1201 b: A mini-Neptune transiting a bright and moderately young M dwarf

Abstract

We present the discovery of a transiting mini-Neptune around TOI-1201, a relatively bright and moderately young early M dwarf (J ≈ 9.5 mag, ~600–800 Myr) in an equal-mass ~8 arcsecond-wide binary system, using data from the Transiting Exoplanet Survey Satellite, 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 Rb = 2.415 ± 0.090 R⊕. 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 Mb = 6.28 ± 0.88 M⊕ and, thus, an estimated bulk density of 2.45−0.42+0.48 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 (Prot = 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 anexcellent target for atmosphere characterization (the transmission spectroscopy metric is 97−16+21) 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.

Hubble Space Telescope Transmission Spectroscopy for the Temperate Sub-Neptune TOI-270 d: A Possible Hydrogen-rich Atmosphere Containing Water Vapor

“…As of 2022 October, the NASA Exoplanet Archive (NASA Exoplanet Archive 2019) 12 reports that there have been 17 transiting exoplanets with radii falling in the 1.8-4 R ⊕ sub-Neptune range, validated around bright (J < 10 mag) M dwarfs. Of these, TESS has discovered 12, namely: AU Mic b and AU Mic c (Plavchan et al 2020;Martioli et al 2021), TOI-1634 b (Cloutier et al 2021;Hirano et al 2021), TOI-270 c and TOI-270 d (Günther et al 2019), TOI-776 b and TOI-776 c (Luque et al 2021), TOI-1201 b (Kossakowski et al 2021), TOI-1231 b (Burt et al 2021), TOI-1266 b (Demory et al 2020;Stefánsson et al 2020), LTT3780 c (Nowak et al 2020;Cloutier et al 2020), and GJ 3090 b (Almenara et al 2022). The other five planets that have been validated to date around bright M dwarfs and with Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence.…”

One year of AU Mic with HARPS – I. Measuring the masses of the two transiting planets

“…Bean, Raymond & Owen 2021 ). To date, there are only a few planets with well-determined masses and radii orbiting stars with well-determined ages below 1 Gyr (Mann et al 2017 ;Barrag án et al 2019bBarrag án et al , 2022aDavid et al 2019b ;Plavchan et al 2020 ;Klein et al 2021 ;Kossakowski et al 2021 ;Su árez Mascare ˜ no et al 2021 ).…”

“…Two of them, K2-100b (Mann et al 2017 ;Barrag án et al 2019b ) and TOI-1201b (Kossakowski et al 2021 ), orbit stars with ages in the range 600-800 Myr. K2-100b is a 3 .…”

GJ 3929: High-precision Photometric and Doppler Characterization of an Exo-Venus and Its Hot, Mini-Neptune-mass Companion

“…Foreman-Mackey 2018) kernels, outlined in more detail in Kossakowski et al (2021). We refer to this as the double simple harmonic oscillator kernel (dSHO).…”