Precise mass and radius of a transiting super-Earth planet orbiting the M dwarf TOI-1235: a planet in the radius gap?

Abstract

We report the confirmation of a transiting planet around the bright weakly active M0.5 V star TOI-1235 (TYC 4384–1735–1, V ≈ 11.5 mag), whose transit signal was detected in the photometric time series of sectors 14, 20, and 21 of the TESS space mission. We confirm the planetary nature of the transit signal, which has a period of 3.44 d, by using precise RV measurements with the CARMENES, HARPS-N, and iSHELL spectrographs, supplemented by high-resolution imaging and ground-based photometry. A comparison of the properties derived for TOI-1235 b with theoretical models reveals that the planet has a rocky composition, with a bulk density slightly higher than that of Earth. In particular, we measure a mass of Mp = 5.9 ± 0.6 M⊕ and a radius of Rp = 1.69 ± 0.08 R⊕, which together result in a density of ρp = 6.7− 1.1+ 1.3 g cm−3. When compared with other well-characterized exoplanetary systems, the particular combination of planetary radius and mass places our discovery in the radius gap, which is a transition region between rocky planets and planets with significant atmospheric envelopes. A few examples of planets occupying the radius gap are known to date. While the exact location of the radius gap for M dwarfs is still a matter of debate, our results constrain it to be located at around 1.7 R⊕ or larger at the insolation levels received by TOI-1235 b (~60 S⊕). This makes it an extremely interesting object for further studies of planet formation and atmospheric evolution.

A Mini-Neptune and a Radius Valley Planet Orbiting the Nearby M2 Dwarf TOI-1266 in Its Venus Zone: Validation with the Habitable-zone Planet Finder

“…From Figure 8, we also note that both LHS 1140b and TOI-1235b-a planet recently discovered and characterized by and Bluhm et al (2020)-have densities consistent with rocky compositions, but both reside above the line measured by Cloutier & Menou (2020), where we would have predicted them to have a nonrocky composition. This could suggest that the transition region could lie slightly higher than measured in Cloutier & Menou (2020).…”

A Close-in Puffy Neptune with Hidden Friends: The Enigma of TOI 620

“…Due to the relatively large TESS pixels spanning 22″ on the sky, fainter visual eclipsing binaries can blend with the nearby bright target stars and produce false positives (barring instrumental artifacts). This is an important consideration, particularly when only a single transiting planet is found in the TESS 27 day time baseline of sector observations, at lower ecliptic latitudes, and away from the ecliptic poles (Lissauer et al 2012;Vanderburg et al 2019;Rodríguez Martínez et al 2020;Hobson et al 2021;Addison et al 2021;Osborn et al 2021;Dreizler et al 2020;Brahm et al 2020;Nowak et al 2020;Teske et al 2020;Sha et al 2021;Gan et al 2021;Bluhm et al 2020).…”

TOI-2046b, TOI-1181b and TOI-1516b, three new hot Jupiters from \textit{TESS}: planets orbiting a young star, a subgiant and a normal star

“…The KESPRINT 1 consortium has been a major contributor for the characterization of gas planets (Smith et al 2019;Johnson et al 2018;Barragán et al 2018;Hjorth et al 2019;Eigmüller et al 2017;Smith et al 2017;Grziwa et al 2016;Johnson et al 2016) found by the K2 mission (Howell et al 2014), and currently also for small planets (Gandolfi et al 2019;Esposito et al 2019;Luque et al 2021;Fridlund et al 2020;Carleo et al 2020;Bluhm et al 2020;Van Eylen et al 2021) found by the TESS mission (Ricker et al 2015). Besides small planets, KESPRINT also led the characterization of the first transiting brown dwarf found by TESS, TOI-503b (Šubjak et al 2020).…”