TOI-1728b: The Habitable-zone Planet Finder confirms a warm super Neptune orbiting an M dwarf host

Abstract

We confirm the planetary nature of TOI-1728b using a combination of ground-based photometry, near-infrared Doppler velocimetry and spectroscopy with the Habitable-zone Planet Finder.TOI-1728 is an old, inactive M0 star with \teff{} $=3980_{-32}^{+31}$ K, which hosts a transiting super Neptune at an orbital period of $\sim$ 3.49 days. Joint fitting of the radial velocities and TESS and ground-based transits yields a planetary radius of $5.05_{-0.17}^{+0.16}$ R${}_{\oplus }$, mass $26.78_{-5.13}^{+5.43}$ M${}_{\oplus }$ and eccentricity $0.057_{-0.039}^{+0.054}$. We estimate the stellar properties, and perform a search for He 10830 Åabsorption during the transit of this planet and claim a null detection with an upper limit of 1.1$\%$ with 90\% confidence. A deeper level of He 10830 Å~ absorption has been detected in the planet atmosphere of GJ 3470b, a comparable gaseous planet. TOI-1728b is the largest super Neptune -- the intermediate subclass of planets between Neptune and the more massive gas-giant planets -- discovered around an M dwarf. With its relatively large mass and radius, TOI-1728 represents a valuable datapoint in the M-dwarf exoplanet mass-radius diagram, bridging the gap between the lighter Neptune-sized planets and the heavier Jovian planets known to orbit M-dwarfs. With a low bulk density of $1.14_{-0.24}^{+0.26}$ g/cm${}^3$, and orbiting a bright host star (J $\sim 9.6$, V $\sim 12.4$), TOI-1728b is also a promising candidate for transmission spectroscopy both from the ground and from space, which can be used to constrain planet formation and evolutionary models.

arXiv comment21 pages, 12 figures, 4 tables: Accepted for publication

References in corpus (92)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Astropy: A Community Python Package for Astronomy
• The NumPy array: a structure for efficient numerical computation
• Gaia Data Release 2. Summary of the contents and survey properties
• The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance
• The Transiting Exoplanet Survey Satellite
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• Correcting for the Effects of Interstellar Extinction
• Analytic Lightcurves for Planetary Transit Searches
• dynesty: A Dynamic Nested Sampling Package for Estimating Bayesian Posteriors and Evidences
• Estimating distances from parallaxes IV: Distances to 1.33 billion stars in Gaia Data Release 2
• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• galpy: A Python Library for Galactic Dynamics
• A 3D Dust Map Based on Gaia, Pan-STARRS 1 and 2MASS
• The Zwicky Transient Facility: Data Processing, Products, and Archive
• The All-Sky Automated Survey for Supernovae (ASAS-SN) Light Curve Server v1.0
• Exploring the Milky Way stellar disk. A detailed elemental abundance study of 714 F and G dwarf stars in the Solar neighbourhood
• Kepler Presearch Data Conditioning II - A Bayesian Approach to Systematic Error Correction
• Fast and scalable Gaussian process modeling with applications to astronomical time series
• Planetary Radii across Five Orders of Magnitude in Mass and Stellar Insolation: Application to Transits
• Models of Stars, Brown Dwarfs and Exoplanets
• Efficient, uninformative sampling of limb darkening coefficients for two-parameter laws
• On the Unique Solution of Planet and Star Parameters from an Extrasolar Planet Transit Light Curve
• The NASA Exoplanet Archive: Data and Tools for Exoplanet Research
• The PPMXL catalog of positions and proper motions on the ICRS. Combining USNO-B1.0 and 2MASS
• astroquery: An Astronomical Web-Querying Package in Python
• Theoretical Transmission Spectra During Extrasolar Giant Planet Transits
• The TESS Input Catalog and Candidate Target List
• Understanding the Mass-Radius Relation for Sub-Neptunes: Radius as a Proxy for Composition
• 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 HARPS search for southern extra-solar planets XXXI. The M-dwarf sample
• A Framework for Prioritizing the TESS Planetary Candidates Most Amenable to Atmospheric Characterization
• Growth Model Interpretation of Planet Size Distribution
• A giant comet-like cloud of hydrogen escaping the warm Neptune-mass exoplanet GJ 436b
• RadVel: The Radial Velocity Modeling Toolkit
• BANYAN. XI. The BANYAN $\Sigma$ multivariate Bayesian algorithm to identify members of young associations within 150 pc
• Improving the Efficiency of Markov Chain Monte Carlo for Analyzing the Orbits of Extrasolar Planets
• The Solar Neighborhood XVII: Parallax Results from the CTIOPI 0.9m Program -- Twenty New Members of the RECONS 10 Parsec Sample
• Spectrum radial velocity analyser (SERVAL). High-precision radial velocities and two alternative spectral indicators
• Estimation of the XUV radiation onto close planets and their evaporation
• The imprint of exoplanet formation history on observable present-day spectra of hot Jupiters
• The HARPS-TERRA project I. Description of the algorithms, performance and new measurements on a few remarkable stars observed by HARPS
• Juliet: a versatile modelling tool for transiting and non-transiting exoplanetary systems
• Structure and evolution of super-Earth to super-Jupiter exoplanets: I. heavy element enrichment in the interior
• Three regimes of extrasolar planets inferred from host star metallicities
• STARRY: Analytic Occultation Light Curves
• PandExo: A Community Tool for Transiting Exoplanet Science with JWST & HST
• A stellar-mass-dependent drop in planet occurrence rates
• Precision Stellar Characterization of FGKM Stars using an Empirical Spectral Library
• Ground-based detection of an extended helium atmosphere in the Saturn-mass exoplanet WASP-69b
• Lyman-$\alpha$ Transit Spectroscopy and the Neutral Hydrogen Tail of the Hot Neptune GJ436b
• Spectrally resolved helium absorption from the extended atmosphere of a warm Neptune-mass exoplanet
• A New Window into Escaping Exoplanet Atmospheres: 10830 Å Line of Helium
• An Increase in the Mass of Planetary Systems around Lower-Mass Stars
• Occurrence Rates of Planets orbiting FGK Stars: Combining Kepler DR25, Gaia DR2 and Bayesian Inference
• Hubble PanCET: An extended upper atmosphere of neutral hydrogen around the warm Neptune GJ 3470 b
• Barycentric Corrections at 1 cm/s for precise Doppler velocities
• The Habitable-Zone Planet Finder: A Stabilized Fiber-Fed NIR Spectrograph for the Hobby-Eberly Telescope
• N-body simulations of planetary accretion around M dwarf stars
• Atmospheric Signatures of Giant Exoplanet Formation by Pebble Accretion
• On the Eccentricity Distribution of Exoplanets from Radial Velocity Surveys
• Fluxes in Hαand Ca II H and K for a sample of Southern stars
• Kepler Planet Occurrence Rates for Mid-Type M Dwarfs as a Function of Spectral Type
• Evolution of the radius valley around low mass stars from $Kepler$ and $K2$
• Ten Year Review of Queue Scheduling of the Hobby-Eberly Telescope
• Analytic Planetary Transit Light Curves and Derivatives for Stars with Polynomial Limb Darkening
• Correcting for Telluric Absorption: Methods, Case Studies, and Release of the TelFit Code
• Planet formation with envelope enrichment: new insights on planetary diversity
• Trends in Atmospheric Properties of Neptune-Size Exoplanets
• High Metallicity and Non-equilibrium Chemistry in the Dayside Atmosphere of hot-Neptune GJ 436b
• Python Leap Second Management and Implementation of Precise Barycentric Correction (barycorrpy)
• The Precision of Mass Measurements Required for Robust Atmospheric Characterization of Transiting Exoplanets
• Ground-based near-UV observations of 15 transiting exoplanets: Constraints on their atmospheres and no evidence for asymmetrical transits
• Measuring the Recoverability of Close Binaries in Gaia DR2 with the Robo-AO Kepler Survey
• Towards Space-like Photometric Precision from the Ground with Beam-Shaping Diffusers
• The Hunt for Exomoons with Kepler (HEK): II. Analysis of Seven Viable Satellite-Hosting Planet Candidates
• Detection of Helium in the Atmosphere of the Exo-Neptune HAT-P-11b
• HAT-P-11: Discovery of a Second Planet and a Clue to Understanding Exoplanet Obliquities
• A Versatile Technique to Enable sub-milli-Kelvin Instrument Stability for Precise Radial Velocity Measurements: Tests with the Habitable-zone Planet Finder
• A He I upper atmosphere around the warm Neptune GJ 3470b
• Evidence for He I 10830 Å~ absorption during the transit of a warm Neptune around the M-dwarf GJ 3470 with the Habitable-zone Planet Finder
• A sub-Neptune sized planet transiting the M2.5-dwarf G 9-40: Validation with the Habitable-zone Planet Finder
• The Ca II infrared triplet's performance as an activity indicator compared to Ca II H and K
• Mass-Radius relationship for M dwarf exoplanets: Comparing nonparametric and parametric methods
• Why do warm Neptunes present nonzero eccentricity?
• Overview of the spectrometer optical fiber feed for the Habitable-zone Planet Finder
• HATS-7b: A Hot Super Neptune Transiting a Quiet K Dwarf Star
• A catalogue of bright (K < 9) M dwarfs
• Information content of JWST-NIRSPEC transmission spectra of warm Neptunes
• Tidal damping of the mutual inclination in hierachical systems
• Spin-driven tidal pumping: Tidally driven changes in planetary spin coupled with secular interactions between planets

Cited by in corpus (19)

• ExoClock Project III: 450 new exoplanet ephemerides from ground and space observations
• TOI-5205 b: A Short-period Jovian Planet Transiting a Mid-M Dwarf
• TOI-3714 b and TOI-3629 b: Two gas giants transiting M dwarfs confirmed with HPF and NEID
• TOI-674b: an oasis in the desert of exo-Neptunes transiting a nearby M dwarf
• Mass and density of the transiting hot and rocky super-Earth LHS 1478 b (TOI-1640 b)
• TOI-532b: The Habitable-zone Planet Finder confirms a Large Super Neptune in the Neptune Desert orbiting a metal-rich M dwarf host
• DREAM: III.A helium survey in exoplanets on the edge of the hot Neptune desert with GIANO-B@TNG
• The LHS 1678 System: Two Earth-Sized Transiting Planets and an Astrometric Companion Orbiting an M Dwarf Near the Convective Boundary at 20 pc
• TOI-3785 b: A Low-Density Neptune Orbiting an M2-Dwarf Star
• Hundreds of TESS exoplanets might be larger than we thought
• VaTEST I: Validation of Sub-Saturn Exoplanet TOI-181b in Narrow Orbit from its Host Star
• A close-in puffy Neptune with hidden friends: The enigma of TOI 620
• Radial velocity confirmation of a hot super-Neptune discovered by TESS with a warm Saturn-mass companion
• Tidally-induced migration of TESS gas giants orbiting M dwarfs
• The GAPS programme at TNG XLIII. A massive brown dwarf orbiting the active M dwarf TOI-5375
• A One-Dimensional Energy Balance Model Parameterization for the Formation of CO2 Ice on the Surfaces of Eccentric Extrasolar Planets
• Homogeneous search for spot transits in Kepler and TESS photometry of K $-$ M-type main-sequence stars
• Confirmation of the hot super-Neptune TOI-672 b with NIRPS and HARPS and Insights into the Neptunian desert around M dwarfs
• TOI-3757 b: A low density gas giant orbiting a solar-metallicity M dwarf