TOI-2285b : A 1.7 Earth-radius planet near the habitable zone around a nearby M dwarf

Summary, in English

We report the discovery of TOI-2285b, a sub-Neptune-sized planet transiting a nearby (42 pc) M dwarf with a period of 27.3 d. We identified the transit signal from the Transiting Exoplanet Survey Satellite photometric data, which we confirmed with ground-based photometric observations using the multiband imagers MuSCAT2 and MuSCAT3. Combining these data with other follow-up observations including high-resolution spectroscopy with the Tillinghast Reflector Echelle Spectrograph, high-resolution imaging with the SPeckle Polarimeter, and radial velocity (RV) measurements with the InfraRed Doppler instrument, we find that the planet has a radius of 1.74 ± 0.08, R⊕, a mass of < 19.5 M⊕ (95% c.l.), and an insolation flux of 1.54 ± 0.14 times that of the Earth. Although the planet resides just outside the habitable zone for a rocky planet, if the planet harbors an H2O layer under a hydrogen-rich atmosphere, then liquid water could exist on the surface of the H2O layer depending on the planetary mass and water mass fraction. The bright host star in the near-infrared (Ks = 9.0) makes this planet an excellent target for further RV and atmospheric observations to improve our understanding of the composition, formation, and habitability of sub-Neptune-sized planets.

• Author: Akihiko Fukui; Tadahiro Kimura; Teruyuki Hirano; Norio Narita; Takanori Kodama; Yasunori Hori; Masahiro Ikoma; Enric Pallé; Felipe Murgas; Hannu Parviainen; Kiyoe Kawauchi; Mayuko Mori; Emma Esparza-Borges; Allyson Bieryla; Jonathan Irwin; Boris S. Safonov; Keivan G. Stassun; Leticia Alvarez-Hernandez; Víctor J.S. Béjar; Núria Casasayas-Barris; Guo Chen; Nicolas Crouzet; Jerome P. De Leon; Keisuke Isogai; Taiki Kagetani; Peter Klagyivik; Judith Korth; Seiya Kurita; Nobuhiko Kusakabe; John Livingston; Rafael Luque; Alberto Madrigal-Aguado; Giuseppe Morello; Taku Nishiumi; Jaume Orell-Miquel; Mahmoudreza Oshagh; Manuel Śanchez-Benavente; Monika Stangret; Yuka Terada; Noriharu Watanabe; Yujie Zou; Motohide Tamura; Takashi Kurokawa; Masayuki Kuzuhara; Jun Nishikawa; Masashi Omiya; Sébastien Vievard; Akitoshi Ueda; David W. Latham; Samuel N. Quinn; Ivan S. Strakhov; Alexandr A. Belinski; Jon M. Jenkins; George R. Ricker; Sara Seager; Roland Vanderspek; Joshua N. Winn; David Charbonneau; David R. Ciardi; Karen A. Collins; John P. Doty; Etienne Bachelet; Daniel Harbeck
• Publishing year: 2022-02-01
• Language: English
• Pages: 1-8
• Publication/Series: Publications of the Astronomical Society of Japan
• Volume: 74
• Issue: 1
• Links: http://dx.doi.org/10.1093/pasj/psab106
• Document type: Journal article
• Publisher: Oxford University Press
• Keywords: planets and satellites: detection; planets and satellites: individual (TOI-2285b); planets and satellites: interiors; techniques: photometric; techniques: radial velocities
• Status: Published
• ISBN/ISSN/Other: ISSN: 0004-6264