Validation and atmospheric exploration of the sub-Neptune TOI-2136b around a nearby M3 dwarf
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
- Planets and satellites: atmospheres
- Planets and satellites: detection
- Planets and satellites: individual: TOI-2136b
- techniques: photometric
- Techniques: radial velocities
- ISSN: 0004-6361