Validation and atmospheric exploration of the sub-Neptune TOI-2136b around a nearby M3 dwarf
Journal article, 2022
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 +/- 0.02 pc, T-eff = 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 R-p = 2.20 +/- 0.07 R-circle plus and a mass of M-p = 4.7(-2.6)(+3.1) M-circle plus. We also search for helium 10830 angstrom absorption lines and place an upper limit on the equivalent width of <7.8 m angstrom 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 H-2-rich atmosphere, making it an excellent target for atmospheric studies to understand the formation, evolution, and habitability of the small planets.
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 +/- 0.02 pc, T-eff = 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 R-p = 2.20 +/- 0.07 R-circle plus and a mass of M-p = 4.7(-2.6)(+3.1) M-circle plus. We also search for helium 10830 angstrom absorption lines and place an upper limit on the equivalent width of <7.8 m angstrom 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 H-2-rich atmosphere, making it an excellent target for atmospheric studies to understand the formation, evolution, and habitability of the small planets.
planets and satellites: detection
techniques: radial velocities
planets and satellites: atmospheres
techniques: photometric
planets and satellites: individual: TOI-2136b
Author
K. Kawauchi
Instituto de Astrofísica de Canarias
University of La Laguna
F. Murgas
Instituto de Astrofísica de Canarias
University of La Laguna
E. Palle
Instituto de Astrofísica de Canarias
University of La Laguna
N. Narita
University of Tokyo
Astrobiology Center, Japan
Instituto de Astrofísica de Canarias
Japan Science and Technology Agency
A. Fukui
University of Tokyo
Instituto de Astrofísica de Canarias
T. Hirano
National Astronomical Observatory of Japan
Astrobiology Center, Japan
H. Parviainen
Instituto de Astrofísica de Canarias
University of La Laguna
H. T. Ishikawa
Astrobiology Center, Japan
National Astronomical Observatory of Japan
N. Watanabe
University of Tokyo
E. Esparaza-Borges
Instituto de Astrofísica de Canarias
University of La Laguna
M. Kuzuhara
Astrobiology Center, Japan
National Astronomical Observatory of Japan
J. Orell-Miquel
Instituto de Astrofísica de Canarias
University of La Laguna
V Krishnamurthy
Astrobiology Center, Japan
National Astronomical Observatory of Japan
M. Mori
University of Tokyo
T. Kagetani
University of Tokyo
Y. Zou
University of Tokyo
K. Isogai
University of Tokyo
Kyoto University
J. H. Livingston
National Astronomical Observatory of Japan
Astrobiology Center, Japan
University of Tokyo
S. B. Howell
National Aeronautics and Space Administration (NASA)
N. Crouzet
European Space Agency (ESA)
J. P. de Leon
University of Tokyo
T. Kimura
University of Tokyo
T. Kodama
University of Tokyo
Judith Korth
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
S. Kurita
University of Tokyo
A. Laza-Ramos
Instituto de Astrofísica de Canarias
R. Luque
Spanish National Research Council (CSIC)
A. Madrigal-Aguado
Instituto de Astrofísica de Canarias
University of La Laguna
K. Miyakawa
Tokyo Institute of Technology
Giuseppe Morello
University of La Laguna
Instituto de Astrofísica de Canarias
T. Nishiumi
Astrobiology Center, Japan
University of Tokyo
The Graduate University for Advanced Studies (SOKENDAI)
G. E. F. Rodriguez
Instituto de Astrofísica de Canarias
M. Sanchez-Benavente
Instituto de Astrofísica de Canarias
University of La Laguna
M. Stangret
University of La Laguna
Instituto de Astrofísica de Canarias
H. Teng
Tokyo Institute of Technology
Y. Terada
Academia Sinica
National Taiwan University
C. L. Gnilka
National Aeronautics and Space Administration (NASA)
California Institute of Technology (Caltech)
N. Guerrero
Massachusetts Institute of Technology (MIT)
University of Florida
H. Harakawa
National Astronomical Observatory of Japan
K. Hodapp
University of Hawaii
Y. Hori
National Astronomical Observatory of Japan
Astrobiology Center, Japan
M. Ikoma
National Astronomical Observatory of Japan
S. Jacobson
University of Hawaii
M. Konishi
Oita University
T. Kotani
Astrobiology Center, Japan
National Astronomical Observatory of Japan
The Graduate University for Advanced Studies (SOKENDAI)
T. Kudo
National Astronomical Observatory of Japan
T. Kurokowa
Astrobiology Center, Japan
Tokyo University of Agriculture and Technology
N. Kusakabe
Astrobiology Center, Japan
National Astronomical Observatory of Japan
J. Nishikawa
National Astronomical Observatory of Japan
Astrobiology Center, Japan
The Graduate University for Advanced Studies (SOKENDAI)
M. Omiya
Astrobiology Center, Japan
National Astronomical Observatory of Japan
T. Serizawa
National Astronomical Observatory of Japan
Tokyo University of Agriculture and Technology
M. Tamura
Astrobiology Center, Japan
National Astronomical Observatory of Japan
University of Tokyo
A. Ueda
The Graduate University for Advanced Studies (SOKENDAI)
Astrobiology Center, Japan
National Astronomical Observatory of Japan
S. Vievard
National Astronomical Observatory of Japan
Astrobiology Center, Japan
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 666 A4Subject Categories (SSIF 2011)
Meteorology and Atmospheric Sciences
Astronomy, Astrophysics and Cosmology
Geophysics
DOI
10.1051/0004-6361/202243381