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Judith Korth



Validation and atmospheric exploration of the sub-Neptune TOI-2136b around a nearby M3 dwarf


  • K. Kawauchi
  • F. Murgas
  • E. Palle
  • N. Narita
  • A. Fukui
  • T. Hirano
  • H. Parviainen
  • H. T. Ishikawa
  • N. Watanabe
  • E. Esparaza-Borges
  • M. Kuzuhara
  • J. Orell-Miquel
  • V. Krishnamurthy
  • M. Mori
  • T. Kagetani
  • Y. Zou
  • K. Isogai
  • J. H. Livingston
  • S. B. Howell
  • N. Crouzet
  • J. P. de Leon
  • T. Kimura
  • T. Kodama
  • J. Korth
  • S. Kurita
  • A. Laza-Ramos
  • R. Luque
  • A. Madrigal-Aguado
  • K. Miyakawa
  • G. Morello
  • T. Nishiumi
  • G. E. F. Rodríguez
  • M. Sánchez-Benavente
  • M. Stangret
  • H. Teng
  • Y. Terada
  • C. L. Gnilka
  • N. Guerrero
  • H. Harakawa
  • K. Hodapp
  • Y. Hori
  • M. Ikoma
  • S. Jacobson
  • M. Konishi
  • T. Kotani
  • T. Kudo
  • T. Kurokowa
  • N. Kusakabe
  • J. Nishikawa
  • M. Omiya
  • T. Serizawa
  • M Tamura
  • A. Ueda
  • S. Vievard

Summary, in English

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

Publishing year





Astronomy and Astrophysics



Document type

Journal article


EDP Sciences


  • Planets and satellites: atmospheres
  • Planets and satellites: detection
  • Planets and satellites: individual: TOI-2136b
  • techniques: photometric
  • Techniques: radial velocities




  • ISSN: 0004-6361