TOI-2285b: A 1.7 Earth-radius Planet Near the Habitable Zone around a Nearby M Dwarf

Abstract

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 days. 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 $\pm$ 0.08 $R_{\oplus }$, a mass of $<$ 19.5 $M_{\oplus }$ (95\% c.l.), and an insolation flux of 1.54 $\pm$ 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 H${}_2$O layer under a hydrogen-rich atmosphere, then liquid water could exist on the surface of the H${}_2$O layer depending on the planetary mass and water mass fraction. The bright host star in the near infrared ($K_s=9.0$) makes this planet an excellent target for further RV and atmospheric observations to improve our understanding on the composition, formation, and habitability of sub-Neptune-sized planets.

9 pages, 3 figures, published online in PASJ

References in corpus (16)

• The Transiting Exoplanet Survey Satellite
• How to Constrain Your M Dwarf: measuring effective temperature, bolometric luminosity, mass, and radius
• A giant comet-like cloud of hydrogen escaping the warm Neptune-mass exoplanet GJ 436b
• Accurate, Empirical Radii and Masses of Planets and their Host Stars with Gaia Parallaxes
• The TESS Objects of Interest Catalog from the TESS Prime Mission
• Precision Stellar Characterization of FGKM Stars using an Empirical Spectral Library
• PyTransit: Fast and Easy Exoplanet Transit Modelling in Python
• A new equation of state for dense hydrogen-helium mixtures
• Habitability and Biosignatures of Hycean Worlds
• AQUA: A Collection of H${}_2$O Equations of State for Planetary Models
• A Spectroscopic Analysis of the California-Kepler Survey Sample: I. Stellar Parameters, Planetary Radii and a Slope in the Radius Gap
• A super-Earth and a sub-Neptune orbiting the bright, quiet M3 dwarf TOI-1266
• Planetary system LHS 1140 revisited with ESPRESSO and TESS
• How Deep Is the Ocean? Exploring the phase structure of water-rich sub-Neptunes
• Precision radial velocity measurements by the forward-modeling technique in the near-infrared
• TOI-1749: an M dwarf with a Trio of Planets including a Near-Resonant Pair

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• Separated twins or just siblings? A multi-planet system around an M dwarf including a cool sub-Neptune
• Earth-like planet predictor: A machine learning approach
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• The Inbound Gas and Dust Evolution of Interstellar Comet 3I/ATLAS from Optical Spectroscopy and Multi-band Photometry