TOI-1235 b: a keystone super-Earth for testing radius valley emergence models around early M dwarfs

Abstract

Small planets on close-in orbits tend to exhibit envelope mass fractions of either effectively zero or up to a few percent depending on their size and orbital period. Models of thermally-driven atmospheric mass loss and of terrestrial planet formation in a gas-poor environment make distinct predictions regarding the location of this rocky/non-rocky transition in period-radius space. Here we present the confirmation of TOI-1235 b ($P=3.44$ days, $r_p=1.738_{-0.076}^{+0.087}$ R${}_{\oplus }$), a planet whose size and period are intermediate between the competing model predictions thus making the system an important test case for emergence models of the rocky/non-rocky transition around early M dwarfs ($R_s=0.630\pm 0.015$ R${}_{\odot }$, $M_s=0.640\pm 0.016$ M${}_{\odot }$). We confirm the TESS planet discovery using reconnaissance spectroscopy, ground-based photometry, high-resolution imaging, and a set of 38 precise radial-velocities from HARPS-N and HIRES. We measure a planet mass of $6.91_{-0.85}^{+0.75}$ M${}_{\oplus }$, which implies an iron core mass fraction of $20_{-12}^{+15}$% in the absence of a gaseous envelope. The bulk composition of TOI-1235 b is therefore consistent with being Earth-like and we constrain a H/He envelope mass fraction to be $<0.5$% at 90% confidence. Our results are consistent with model predictions from thermally-driven atmospheric mass loss but not with gas-poor formation, suggesting that the former class of processes remain efficient at sculpting close-in planets around early M dwarfs. Our RV analysis also reveals a strong periodicity close to the first harmonic of the photometrically-determined stellar rotation period that we treat as stellar activity, despite other lines of evidence favoring a planetary origin ($P=21.8_{-0.8}^{+0.9}$ days, $m_p\sin i=13.0_{-5.3}^{+3.8}$ M${}_{\oplus }$) that cannot be firmly ruled out by our data.

arXiv commentAccepted to The Astronomical Journal. 8 figures & 5 tables. Table 2 is provided in the arXiv source code

References in corpus (112)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Astropy: A Community Python Package for Astronomy
• emcee: The MCMC Hammer
• The Sloan Digital Sky Survey: Technical Summary
• Gaia Data Release 2. Summary of the contents and survey properties
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• The Transiting Exoplanet Survey Satellite
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• Analytic Lightcurves for Planetary Transit Searches
• Gaia Data Release 2: The astrometric solution
• The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets
• Las Cumbres Observatory Global Telescope Network
• batman: BAsic Transit Model cAlculatioN in Python
• 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
• Planetary Radii across Five Orders of Magnitude in Mass and Stellar Insolation: Application to Transits
• A box-fitting algorithm in the search for periodic transits
• The stellar activity-rotation relationship and the evolution of stellar dynamos
• Kepler Presearch Data Conditioning I - Architecture and Algorithms for Error Correction in Kepler Light Curves
• A super-Earth transiting a nearby low-mass star
• Kepler planets: a tale of evaporation
• Most 1.6 Earth-Radius Planets are not Rocky
• The evaporation valley in the Kepler planets
• Gaia Data Release 2: Photometric content and validation
• EXOFAST: A fast exoplanetary fitting suite in IDL
• How to Constrain Your M Dwarf: measuring effective temperature, bolometric luminosity, mass, and radius
• 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 Mass-Radius Relation for 65 Exoplanets Smaller than 4 Earth Radii
• Growth Model Interpretation of Planet Size Distribution
• The California Kepler Survey VII. Precise Planet Radii Leveraging Gaia DR2 Reveal the Stellar Mass Dependence of the Planet Radius Gap
• An asteroseismic view of the radius valley: stripped cores, not born rocky
• The Role of Core Mass in Controlling Evaporation: the Kepler Radius Distribution and the Kepler-36 Density Dichotomy
• Core-powered mass loss and the radius distribution of small exoplanets
• Accurate, Empirical Radii and Masses of Planets and their Host Stars with Gaia Parallaxes
• The NextGen Model Atmosphere grid: II. Spherically symmetric model atmospheres for giant stars with effective temperatures between 3000 and 6800~K
• Revised Catalog of GALEX Ultraviolet Sources. I. The All-sky Survey: GUVcat_AIS
• Design Considerations for a Ground-based Transit Search for Habitable Planets Orbiting M dwarfs
• The California Planet Survey I. Four New Giant Exoplanets
• Sculpting the Valley in the Radius Distribution of Small Exoplanets as a by-product of Planet Formation: The Core-Powered Mass-Loss Mechanism
• How Thermal Evolution and Mass Loss Sculpt Populations of Super-Earths and Sub-Neptunes: Application to the Kepler-11 System and Beyond
• The HARPS-TERRA project I. Description of the algorithms, performance and new measurements on a few remarkable stars observed by HARPS
• The H$\alpha$ emission of nearby M dwarfs and its relation to stellar rotation
• Planetary population synthesis coupled with atmospheric escape: a statistical view of evaporation
• A temperate rocky super-Earth transiting a nearby cool star
• STARRY: Analytic Occultation Light Curves
• Evidence for a systematic offset of -80 micro-arcseconds in the Gaia DR2 parallaxes
• Atmospheres of protoplanetary cores: critical mass for nucleated instability
• Parametrizing the exoplanet eccentricity distribution with the Beta distribution
• Kepler Data Validation I -- Architecture, Diagnostic Tests, and Data Products for Vetting Transiting Planet Candidates
• A new list of thorium and argon spectral lines in the visible
• Precision Stellar Characterization of FGKM Stars using an Empirical Spectral Library
• A simple method to estimate radial velocity variations due to stellar activity using photometry
• Understanding The Effects Of Stellar Multiplicity On The Derived Planet Radii From Transit Surveys: Implications for Kepler, K2, and TESS
• Super-Earth Atmospheres: Self-Consistent Gas Accretion and Retention
• Breeding Super-Earths and Birthing Super-Puffs in Transitional Disks
• Compositional imprints in density-distance-time: a rocky composition for close-in low-mass exoplanets from the location of the valley of evaporation
• The rotation and Galactic kinematics of mid M dwarfs in the Solar Neighborhood
• Make Super-Earths, Not Jupiters: Accreting Nebular Gas onto Solid Cores at 0.1 AU and Beyond
• SOAP 2.0: A tool to estimate the photometric and radial velocity variations induced by stellar spots and plages
• An Efficient Automated Validation Procedure for Exoplanet Transit Candidates
• The Ultraviolet Radiation Environment Around M dwarf Exoplanet Host Stars
• On the angular momentum evolution of fully-convective stars: rotation periods for field M-dwarfs from the MEarth transit survey
• Inevitability of Plate Tectonics on Super-Earths
• A Detailed Model Grid for Solid Planets from 0.1 through 100 Earth Masses
• 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
• To Cool is to Accrete: Analytic Scalings for Nebular Accretion of Planetary Atmospheres
• The Mass of Kepler-93b and The Composition of Terrestrial Planets
• Evolutionary Analysis of Gaseous Sub-Neptune-Mass Planets with MESA
• Detecting Planets Around Very Low Mass Stars with the Radial Velocity Method
• The Solar Neighborhood XXXVII: The Mass-Luminosity Relation for Main Sequence M Dwarfs
• Eclipsing Binary Stars as Benchmarks for Trigonometric Parallaxes in the Gaia Era
• Signatures of the Core-Powered Mass-Loss Mechanism in the Exoplanet Population: Dependence on Stellar Properties and Observational Predictions
• The Chemical Homogeneity of Sun-like Stars in the Solar Neighborhood
• Empirical, Accurate Masses and Radii of Single Stars with TESS and Gaia
• Transit Detection in the MEarth Survey of Nearby M Dwarfs: Bridging the Clean-First, Search-Later Divide
• 275 Candidates and 149 Validated Planets Orbiting Bright Stars in K2 Campaigns 0-10
• Evolution of the radius valley around low mass stars from $Kepler$ and $K2$
• Vetting of 384 TESS Objects of Interest with TRICERATOPS and Statistical Validation of 12 Planet Candidates
• Minimum Radii of Super-Earths: Constraints from Giant Impacts
• How formation time-scales affect the period dependence of the transition between rocky super-Earths and gaseous sub-Neptunes and implications for ${\eta }_{\oplus }$
• BGLS: A Bayesian formalism for the generalised Lomb-Scargle periodogram
• A hot Uranus transiting the nearby M dwarf GJ3470. Detected with HARPS velocimetry. Captured in transit with TRAPPIST photometry
• Planetary system around the nearby M dwarf GJ 357 including a transiting, hot, Earth-sized planet optimal for atmospheric characterization
• Mass and Mass Scalings of Super-Earths
• A Spectroscopic Analysis of the California-Kepler Survey Sample: I. Stellar Parameters, Planetary Radii and a Slope in the Radius Gap
• A path towards understanding the rotation-activity relation of M dwarfs with K2 mission, X-ray and UV data
• EXOFASTv2: A public, generalized, publication-quality exoplanet modeling code
• A Catalog of Cool Dwarf Targets for the Transiting Exoplanet Survey Satellite
• A second terrestrial planet orbiting the nearby M dwarf LHS 1140
• Stacked Bayesian general Lomb-Scargle periodogram: Identifying stellar activity signals
• A pair of TESS planets spanning the radius valley around the nearby mid-M dwarf LTT 3780
• On the use of marginal posteriors in marginal likelihood estimation via importance-sampling
• HARPS-N Solar Radial-Velocity Variations Are Dominated By Large, Bright Magnetic Regions
• The Monitor project: Rotation of low-mass stars in the open cluster M34
• Testing exoplanet evaporation with multi-transiting systems
• Characterization of the L 98-59 multi-planetary system with HARPS: two confirmed terrestrial planets and a mass upper limit on the third
• Radial velocity follow-up of GJ1132 with HARPS. A precise mass for planet 'b' and the discovery of a second planet
• Confirmation of the radial velocity super-Earth K2-18c with HARPS and CARMENES
• Quantifying the Bayesian Evidence for a Planet in Radial Velocity Data
• A hot terrestrial planet orbiting the bright M dwarf L 168-9 unveiled by TESS
• Characterizing the Near-UV Environment of M Dwarfs
• GJ 1252 b: A 1.2 $R_{\oplus }$ planet transiting an M3-dwarf at 20.4 pc
• Exoplanet Imitators: A test of stellar activity behavior in radial velocity signals
• Eyes on K2-3: A system of three likely sub-Neptunes characterized with HARPS-N and HARPS
• Meeting the Cool Neighbours, II: Photometry of southern NLTT stars
• The Near-Ultraviolet Luminosity Function of Young, Early M-Type Dwarf Stars
• The independent discovery of planet candidates around low mass stars and astrophysical false positives from the first two TESS sectors

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