Masses and radii for the three super-Earths orbiting GJ 9827, and implications for the composition of small exoplanets

Abstract

Super-Earths belong to a class of planet not found in the Solar System, but which appear common in the Galaxy. Given that some super-Earths are rocky, while others retain substantial atmospheres, their study can provide clues as to the formation of both rocky planets and gaseous planets, and - in particular - they can help to constrain the role of photo-evaporation in sculpting the exoplanet population. GJ 9827 is a system already known to host 3 super-Earths with orbital periods of 1.2, 3.6 and 6.2 days. Here we use new HARPS-N radial velocity measurements, together with previously published radial velocities, to better constrain the properties of the GJ 9827 planets. Our analysis can't place a strong constraint on the mass of GJ 9827 c, but does indicate that GJ 9827 b is rocky with a composition that is probably similar to that of the Earth, while GJ 9827 d almost certainly retains a volatile envelope. Therefore, GJ 9827 hosts planets on either side of the radius gap that appears to divide super-Earths into pre-dominantly rocky ones that have radii below $\sim 1.5R_{\oplus }$, and ones that still retain a substantial atmosphere and/or volatile components, and have radii above $\sim 2R_{\oplus }$. That the less heavily irradiated of the 3 planets still retains an atmosphere, may indicate that photoevaporation has played a key role in the evolution of the planets in this system.

arXiv comment16 pages, 9 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society

References in corpus (69)

• emcee: The MCMC Hammer
• Gaia Data Release 2. Summary of the contents and survey properties
• The Gaia mission
• Validation of the new Hipparcos reduction
• MultiNest: an efficient and robust Bayesian inference tool for cosmology and particle physics
• MESA Isochrones and Stellar Tracks (MIST) 0: Methods for the construction of stellar isochrones
• The Dartmouth Stellar Evolution Database
• Multimodal nested sampling: an efficient and robust alternative to MCMC methods for astronomical data analysis
• Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1
• The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets
• Astrophysics Source Code Library
• Planet Occurrence within 0.25 AU of Solar-type Stars from Kepler
• batman: BAsic Transit Model cAlculatioN in Python
• Local stellar kinematics from Hipparcos data
• Planetary Candidates Observed by Kepler, III: Analysis of the First 16 Months of Data
• Efficient, uninformative sampling of limb darkening coefficients for two-parameter laws
• Kepler planets: a tale of evaporation
• Most 1.6 Earth-Radius Planets are not Rocky
• Theoretical Transmission Spectra During Extrasolar Giant Planet Transits
• The evaporation valley in the Kepler planets
• Understanding the Mass-Radius Relation for Sub-Neptunes: Radius as a Proxy for Composition
• Probabilistic Forecasting of the Masses and Radii of Other Worlds
• A Technique for Extracting Highly Precise Photometry for the Two-Wheeled Kepler Mission
• The Mass-Radius Relation for 65 Exoplanets Smaller than 4 Earth Radii
• The CORALIE survey for southern extra-solar planets VII. Two short-period Saturnian companions to HD108147 and HD168746
• A giant comet-like cloud of hydrogen escaping the warm Neptune-mass exoplanet GJ 436b
• The California Kepler Survey VII. Precise Planet Radii Leveraging Gaia DR2 Reveal the Stellar Mass Dependence of the Planet Radius Gap
• Planets and Stellar Activity: Hide and Seek in the CoRoT-7 system
• 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
• Spectrum radial velocity analyser (SERVAL). High-precision radial velocities and two alternative spectral indicators
• Measuring the rotation period distribution of field M-dwarfs with Kepler
• The Minimum-Mass Extrasolar Nebula: In-Situ Formation of Close-In Super-Earths
• Mass-Radius Relation for Rocky Planets based on PREM
• How Thermal Evolution and Mass Loss Sculpt Populations of Super-Earths and Sub-Neptunes: Application to the Kepler-11 System and Beyond
• Three regimes of extrasolar planets inferred from host star metallicities
• Precision Stellar Characterization of FGKM Stars using an Empirical Spectral Library
• Eccentricity from transit photometry: small planets in Kepler multi-planet systems have low eccentricities
• Super-Earth Atmospheres: Self-Consistent Gas Accretion and Retention
• Formation and Structure of Low Density Exo-Neptunes
• Water loss from Earth-sized planets in the habitable zones of ultracool dwarfs: Implications for the planets of TRAPPIST-1
• Inferring probabilistic stellar rotation periods using Gaussian processes
• An Earth-sized planet with an Earth-like density
• Planetary Candidates from the First Year of the K2 Mission
• Tidal Locking of Habitable Exoplanets
• Oxygen trends in the Galactic thin and thick disks
• The radius discrepancy in low mass stars: single vs. binaries
• Radius Dependent Angular Momentum Evolution in Low-Mass Stars. I
• 275 Candidates and 149 Validated Planets Orbiting Bright Stars in K2 Campaigns 0-10
• The Formation of Super-Earths and Mini-Neptunes with Giant Impacts
• Born Dry in the Photo-Evaporation Desert: Kepler's Ultra-Short-Period Planets Formed Water-Poor
• Determining the Mass of Kepler-78b With Nonparametric Gaussian Process Estimation
• 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
• Strong XUV irradiation of the Earth-sized exoplanets orbiting the ultracool dwarf TRAPPIST-1
• An ultra-short period rocky super-Earth with a secondary eclipse and a Neptune-like companion around K2-141
• The GAPS programme with HARPS-N at TNG XI. Pr~0211 in M~44: the first multi-planet system in an open cluster
• Water/Icy Super-Earths: Giant Impacts and Maximum Water Content
• Two Small Planets Transiting HD 3167
• Three Small Super-Earths Transiting the nearby star GJ 9827
• The Rotation-Activity Correlations in K and M dwarfs. I. Stellar parameters, compilations of $v\sin i$ and $P/\sin i$ for a large sample of late-K and M dwarfs
• Tidal dissipation and eccentricity pumping: Implications for the depth of the secondary eclipse of 55 Cnc e
• Eyes on K2-3: A system of three likely sub-Neptunes characterized with HARPS-N and HARPS
• Plausible Compositions of the Seven TRAPPIST-1 Planets Using Long-term Dynamical Simulations
• A System of Three Super Earths Transiting the Late K-Dwarf GJ 9827 at Thirty Parsecs
• Mass determination of the 1:3:5 near-resonant planets transiting GJ 9827 (K2-135)
• An accurate mass determination for Kepler-1655b, a moderately-irradiated world with a significant volatile envelope
• Magellan/PFS Radial Velocities of GJ 9827, a late K dwarf at 30 pc with Three Transiting Super-Earths

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• Absence of extended atmospheres in low-mass star radius-gap planets GJ 9827 b, GJ 9827 d and TOI-1235 b
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