Author:
Kawauchi K.,Murgas F.,Palle E.,Narita N.,Fukui A.,Hirano T.,Parviainen H.,Ishikawa H. T.,Watanabe N.,Esparaza-Borges E.,Kuzuhara M.,Orell-Miquel J.,Krishnamurthy V.,Mori M.,Kagetani T.,Zou Y.,Isogai K.,Livingston J. H.,Howell S. B.,Crouzet N.,de Leon J. P.,Kimura T.,Kodama T.,Korth J.,Kurita S.,Laza-Ramos A.,Luque R.,Madrigal-Aguado A.,Miyakawa K.,Morello G.,Nishiumi T.,Rodríguez G. E. F.,Sánchez-Benavente M.,Stangret M.,Teng H.,Terada Y.,Gnilka C. L.,Guerrero N.,Harakawa H.,Hodapp K.,Hori Y.,Ikoma M.,Jacobson S.,Konishi M.,Kotani T.,Kudo T.,Kurokowa T.,Kusakabe N.,Nishikawa J.,Omiya M.,Serizawa T.,Tamura M.,Ueda A.,Vievard S.
Abstract
Context. The NASA space telescope TESS is currently in the extended mission of its all-sky search for new transiting planets. Of the thousands of candidates that TESS is expected to deliver, transiting planets orbiting nearby M dwarfs are particularly interesting targets since they provide a great opportunity to characterize their atmospheres by transmission spectroscopy.
Aims. We aim to validate and characterize the new sub-Neptune-sized planet candidate TOI-2136.01 orbiting a nearby M dwarf (d = 33.36 ± 0.02pc, Teff = 3373 ± 108 K) with an orbital period of 7.852 days.
Methods. We use TESS data, ground-based multicolor photometry, and radial velocity measurements with the InfraRed Doppler (IRD) instrument on the Subaru Telescope to validate the planetary nature of TOI-2136.01, and estimate the stellar and planetary parameters. We also conduct high-resolution transmission spectroscopy to search for helium in its atmosphere.
Results. We confirm that TOI-2136.01 (now named TOI-2136b) is a bona fide planet with a planetary radius of Rp = 2.20 ± 0.07R⊕ and a mass of Mp = 4.7−2.6+3.1 M⊕. We also search for helium 10830 Å absorption lines and place an upper limit on the equivalent width of <7.8 mÅ and on the absorption signal of <1.44% with 95% confidence.
Conclusions. TOI-2136b is a sub-Neptune transiting a nearby and bright star (J = 10.8 mag), and is a potentially hycean planet, which is a new class of habitable planets with large oceans under a H2-rich atmosphere, making it an excellent target for atmospheric studies to understand the formation, evolution, and habitability of the small planets.
Subject
Space and Planetary Science,Astronomy and Astrophysics
Cited by
6 articles.
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