Multicolour Validation of Two Temperate Mini-Neptunes Around M-dwarf Habitable Zones

Abstract

For small planets orbiting within the habitable zones of their host stars, multicolour validation via photometric transit observations offers an efficient alternative to prioritize targets before intensive radial-velocity follow-up, thereby expanding the sample of habitable-zone exoplanets amenable for atmospheric characterisation. In this study, we validate two exceptional habitable-zone TESS candidates, orbiting around M-dwarfs, as genuine planets, precisely determining their transit and physical parameters. We perform Bayesian model comparison by jointly fitting multicolour light curves from TESS and ground-based follow-up, including observations with HiPERCAM at the 10.4-m GTC. Our approach uses wavelength-dependent transit depth variations and precise transit geometry to reject false positives. We validate TOI-2094 b and TOI-7166 b as two new benchmark temperate mini-Neptunes. TOI-2094 b (1.90 $R_{\oplus }$) orbits its M3V star with a period of $\sim$18.79 days, well within the habitable zone ($\sim$0.98 Earth insolation). TOI-7166 b (2.39 $R_{\oplus }$) orbits its M4.5V host star with a period of $\sim$12.92 days, placing it near the inner edge of the habitable zone ($\sim$1.93 Earth insolation). Statistical mass and density estimates suggest that TOI-2094 b may be a volatile-rich planet, such as a water world or a gaseous planet, and is less likely to be rocky, while TOI-7166 b is likely to be volatile-rich. Both planets are of great interest for detailed atmospheric characterisation with the JWST and future ELTs, which requires further precise mass measurements.

18 pages, 14 figures, published in MNRAS

References in corpus (67)

• The Gaia mission
• Gaia Data Release 3: Summary of the content and survey properties
• The Transiting Exoplanet Survey Satellite
• MultiNest: an efficient and robust Bayesian inference tool for cosmology and particle physics
• A new extensive library of PHOENIX stellar atmospheres and synthetic spectra
• X-ray spectral modelling of the AGN obscuring region in the CDFS: Bayesian model selection and catalogue
• Habitable Zones Around Main-Sequence Stars: New Estimates
• Bayes in the sky: Bayesian inference and model selection in cosmology
• Kepler Presearch Data Conditioning II - A Bayesian Approach to Systematic Error Correction
• Fast and scalable Gaussian process modeling with applications to astronomical time series
• The Revised TESS Input Catalog and Candidate Target List
• Models of Stars, Brown Dwarfs and Exoplanets
• Kepler Presearch Data Conditioning I - Architecture and Algorithms for Error Correction in Kepler Light Curves
• The TESS Input Catalog and Candidate Target List
• AstroImageJ: Image Processing and Photometric Extraction for Ultra-Precise Astronomical Light Curves (Expanded Edition)
• AstroImageJ: Image Processing and Photometric Extraction for Ultra-Precise Astronomical Light Curves
• The Near-Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope I. Overview of the instrument and its capabilities
• The Pan-STARRS1 Database and Data Products
• A Framework for Prioritizing the TESS Planetary Candidates Most Amenable to Atmospheric Characterization
• Growth Model Interpretation of Planet Size Distribution
• The Mass-Radius Relation for 65 Exoplanets Smaller than 4 Earth Radii
• petitRADTRANS: a Python radiative transfer package for exoplanet characterization and retrieval
• The TESS Objects of Interest Catalog from the TESS Prime Mission
• A temperate rocky super-Earth transiting a nearby cool star
• PandExo: A Community Tool for Transiting Exoplanet Science with JWST & HST
• How to Distinguish between Cloudy Mini-Neptunes and Water/Volatile-Dominated Super-Earths
• Kepler Data Validation I -- Architecture, Diagnostic Tests, and Data Products for Vetting Transiting Planet Candidates
• Density, not radius, separates rocky and water-rich small planets orbiting M dwarf stars
• The CHEOPS mission
• Planetary nebulae seen with TESS: Discovery of new binary central star candidates from Cycle 1
• Real-time processing of the imaging data from the network of Las Cumbres Observatory Telescopes using BANZAI
• Kepler Data Validation II -- Transit Model Fitting and Multiple-Planet Search
• Revisited Mass-Radius relations for exoplanets below 120 Earth masses
• PyTransit: Fast and Easy Exoplanet Transit Modelling in Python
• LDTk: Limb Darkening Toolkit
• A Guide to Realistic Uncertainties on Fundamental Properties of Solar-Type Exoplanet Host Stars
• In-orbit Performance of the Near-Infrared Spectrograph NIRSpec on the James Webb Space Telescope
• Vetting of 384 TESS Objects of Interest with TRICERATOPS and Statistical Validation of 12 Planet Candidates
• The Mid-Infrared Instrument for the James Webb Space Telescope: IV. The Low Resolution Spectrometer
• ARIADNE: Measuring accurate and precise stellar parameters through SED fitting
• The Precision of Mass Measurements Required for Robust Atmospheric Characterization of Transiting Exoplanets
• The First Habitable Zone Earth-sized Planet from TESS. I: Validation of the TOI-700 System
• HiPERCAM: a quintuple-beam, high-speed optical imager on the 10.4-m Gran Telescopio Canarias
• The Nordic Optical Telescope
• Multicolour photometry for exoplanet candidate validation
• MuSCAT2: four-color Simultaneous Camera for the 1.52-m Telescopio Carlos Sánchez
• Model Atmospheres From Very Low Mass Stars to Brown Dwarfs
• From super-Earths to sub-Neptunes: Observational constraints and connections to theoretical models
• MuSCAT2 multicolour validation of TESS candidates: an ultra-short-period substellar object around an M dwarf
• The Near Infrared Imager and Slitless Spectrograph for the James Webb Space Telescope -- III. Single Object Slitless Spectroscopy
• From cold to hot irradiated gaseous exoplanets: Fingerprints of chemical disequilibrium in atmospheric spectra
• TOI-2076 and TOI-1807: Two young, comoving planetary systems within 50 pc identified by TESS that are ideal candidates for further follow-up
• The First Habitable Zone Earth-Sized Planet From TESS II: $Spitzer$ Confirms TOI-700 d
• Atmospheric retrievals suggest the presence of a secondary atmosphere and possible sulfur species on L 98-59 d from JWST NIRSpec G395H transmission spectroscopy
• ShaneAO: wide science spectrum adaptive optics system for the Lick Observatory
• APOGEE Net: An expanded spectral model of both low mass and high mass stars
• Quantifying the Observational Effort Required for the Radial Velocity Characterization of TESS Planets
• A 1.55 R${}_{\oplus }$ habitable-zone planet hosted by TOI-715, an M4 star near the ecliptic South Pole
• JWST Reveals CH${}_4$, CO${}_2$, and H${}_2$O in a Metal-rich Miscible Atmosphere on a Two-Earth-Radius Exoplanet
• Commissioning ShARCS: the Shane Adaptive optics infraRed Camera-Spectrograph for the Lick Observatory 3-m telescope
• Day-night transport induced chemistry and clouds on WASP-39b I: Gas-phase composition
• A hot sub-Neptune in the desert and a temperate super-Earth around faint M dwarfs: Color validation of TOI-4479b and TOI-2081b
• RoadRunner: a fast and flexible exoplanet transit model
• TESS discovery of two super-Earths orbiting the M-dwarf stars TOI-6002 and TOI-5713 near the radius valley
• Validation of up to seven TESS planet candidates through multi-colour transit photometry using MuSCAT2 data
• JWST-TST DREAMS: Sulfur dioxide in the atmosphere of the Neptune-mass planet HAT-P-26 b from NIRSpec G395H transmission spectroscopy
• Combined Exoplanet Mass and Atmospheric Characterization for Accelerated Exoplanetology