Close-in Super-Earths: The first and the last stages of planet formation in an MRI-accreting disc

Abstract

We explore in situ formation and subsequent evolution of close-in super-Earths and mini-Neptunes. We adopt a steady-state inner protoplanetary gas disc structure that arises from viscous accretion due to the magneto-rotational instability (MRI). We consider the evolution of dust in the inner disc, including growth, radial drift and fragmentation, and find that dust particles that radially drift into the inner disc fragment severely due to the MRI-induced turbulence. This result has two consequences: (1) radial drift of grains within the inner disc is quenched, leading to an enhancement of dust in the inner regions which scales as dust-to-gas-mass-flux-ratio at ~1 AU; (2) however, despite this enhancement, planetesimal formation is impeded by the small grain size. Nevertheless, assuming that planetary cores are present in the inner disc, we then investigate the accretion of atmospheres onto cores and their subsequent photoevaporation. We then compare our results to the observed exoplanet mass-radius relationship. We find that: (1) the low gas surface densities and high temperatures in the inner disc reduce gas accretion onto cores compared to the minimum mass solar nebula, preventing the cores from growing into hot Jupiters, in agreement with the data; (2) however, our predicted envelope masses are still typically larger than observed ones. Finally, we sketch a qualitative picture of how grains may grow and planetesimals form in the inner disc if grain effects on the ionization levels and the MRI and the back-reaction of the dust on the gas (both neglected in our calculations) are accounted for.

arXiv commentAccepted for publication in MNRAS

References in corpus (95)

• The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets
• Streaming Instabilities in Protoplanetary Disks
• The false positive rate of Kepler and the occurrence of planets
• Planetary Candidates Observed by Kepler, III: Analysis of the First 16 Months of Data
• Characteristics of planetary candidates observed by Kepler, II: Analysis of the first four months of data
• The effects of snowlines on C/O in planetary atmospheres
• The Occurrence and Architecture of Exoplanetary Systems
• A simple model for the evolution of the dust population in protoplanetary disks
• Kepler planets: a tale of evaporation
• The evaporation valley in the Kepler planets
• Planet-disk interaction and orbital evolution
• Understanding the Mass-Radius Relation for Sub-Neptunes: Radius as a Proxy for Composition
• Coagulation, fragmentation and radial motion of solid particles in protoplanetary disks
• Gas- and dust evolution in protoplanetary disks
• Particle Stirring in Turbulent Gas Disks: Including Orbital Oscillations
• The California Kepler Survey VII. Precise Planet Radii Leveraging Gaia DR2 Reveal the Stellar Mass Dependence of the Planet Radius Gap
• 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
• Planetesimal Formation by Gravitational Instability
• Protoplanetary Disk Turbulence Driven by the Streaming Instability: Non-Linear Saturation and Particle Concentration
• Closed-form expressions for particle relative velocities induced by turbulence
• The Minimum-Mass Extrasolar Nebula: In-Situ Formation of Close-In Super-Earths
• Radial Flow of Dust Particles in Accretion Disks
• Ring shaped dust accumulation in transition disks
• Magnetorotational Instability in Protoplanetary Disks. II. Ionization State and Unstable Regions
• Particle Clumping and Planetesimal Formation Depend Strongly on Metallicity
• Breaking the Chains: Hot Super-Earth systems from migration and disruption of compact resonant chains
• Atmospheres of protoplanetary cores: critical mass for nucleated instability
• A stellar-mass-dependent drop in planet occurrence rates
• Concentrating small particles in protoplanetary disks through the streaming instability
• Migration then assembly: Formation of Neptune mass planets inside 1 AU
• Breeding Super-Earths and Birthing Super-Puffs in Transitional Disks
• Initial Conditions of Planet Formation: Lifetimes of Primordial Disks
• The TW Hya Disk at 870 microns: Comparison of CO and Dust Radial Structures
• Formation and Structure of Low Density Exo-Neptunes
• Make Super-Earths, Not Jupiters: Accreting Nebular Gas onto Solid Cores at 0.1 AU and Beyond
• How to form planetesimals from mm-sized chondrules and chondrule aggregates
• Hot super-Earths stripped by their host stars
• Testing In Situ Assembly with the Kepler Planet Candidate Sample
• Probabilistic Mass-Radius Relationship for Sub-Neptune-Sized Planets
• The Extreme Ultraviolet and X-Ray Sun in Time: High-Energy Evolutionary Tracks of a Solar-Like Star
• 55 Cancri (Copernicus): A Multi-Planet System with a Hot Super-Earth and a Jupiter Analogue
• Magnetic fields in protoplanetary disks
• The Exoplanet Population Observation Simulator. I - The Inner Edges of Planetary Systems
• To Cool is to Accrete: Analytic Scalings for Nebular Accretion of Planetary Atmospheres
• The coronal X-ray - age relation and its implications for the evaporation of exoplanets
• Composition and fate of short-period super-Earths: The case of CoRoT-7b
• Inside-Out Planet Formation
• Atmospheres of low-mass planets: the "boil-off"
• Evolution of Protoplanetary Discs with Magnetically Driven Disc Winds
• Close-in planetesimal formation by pile-up of drifting pebbles
• In-situ Accretion of Hydrogen-Rich Atmospheres on Short-Period Super-Earths: Implications for the Kepler-11 Planets
• Effect of Ambipolar Diffusion on the Non-linear Evolution of Magnetorotational Instability in Weakly Ionized Disks
• Overstable Librations can account for the Paucity of Mean Motion Resonances among Exoplanet Pairs
• Hydrodynamics of Embedded Planets' First Atmospheres. II. A Rapid Recycling of Atmospheric Gas
• Heat and Dust in Active Layers of Protostellar Disks
• Trapping Solids at the Inner Edge of the Dead Zone: 3-D Global MHD Simulations
• Magnetorotational Instability Driven Accretion in Protoplanetary Disks
• On the Ionisation Fraction in Protoplanetary Disks I: Comparing Different Reaction Networks
• The Formation of Super-Earths and Mini-Neptunes with Giant Impacts
• Planetesimal formation by the streaming instability in a photoevaporating disk
• Hot super-Earths and giant planet cores from different migration histories
• Particle Pile-ups and Planetesimal Formation
• Secure TTV Mass Measurements: Ten Kepler Exoplanets between 3 and 8 Earth Masses with Diverse Densities and Incident Fluxes
• The Physics of Protoplanetesimal Dust Agglomerates. III. Compaction in Multiple Collisions
• Magnetospheric Truncation, Tidal Inspiral, and the Creation of Short and Ultra-Short Period Planets
• Hydrodynamics of embedded planets' first atmospheres - III. The role of radiation transport for super-Earth planets
• Low-velocity collisions of centimeter-sized dust aggregates
• HST measures of Mass Accretion Rates in the Orion Nebula Cluster
• A reassessment of the in situ formation of close-in super-Earths
• Stealing the Gas: Giant Impacts and the Large Diversity in Exoplanet Densities
• The 3D Flow Field Around an Embedded Planet
• The Structure of the Evolved Circumbinary Disk around V4046 Sgr
• Assembling the Building Blocks of Giant Planets around Intermediate Mass Stars
• A break in the gas and dust surface density of the disc around the T Tauri star IM Lup
• Giant Impact: An Efficient Mechanism for the Devolatilization of Super-Earths
• Formation of close-in super-Earths in evolving protoplanetary disks due to disk winds
• Dynamical rearrangement of super-Earths during disk dispersal I. Outline of the magnetospheric rebound model
• Resonant drag instability of grains streaming in fluids
• On the nature of the transition disk around LkCa 15
• Planetesimal formation via sweep-up growth at the inner edge of dead zones
• The Physics of Protoplanetesimal Dust Agglomerates. Vi. Erosion of Large Aggregates as a Source of Micrometer-Sized Particles
• Dust and gas density evolution at a radial pressure bump in protoplanetary disks
• The Physics of Protoplanetesimal Dust Agglomerates. V. Multiple Impacts of Dusty Agglomerates at Velocities Above the Fragmentation Threshold
• The physics of protoplanetesimal dust agglomerates. VII The low-velocity collision behavior of large dust agglomerates
• Growth and fragmentation of centimetre-sized dust aggregates: the dependence on aggregate size and porosity
• Using Ice and Dust Lines to Constrain the Surface Densities of Protoplanetary Disks
• Convergence zones for Type I migration: an inward shift for multiple planet systems
• The role of pebble fragmentation in planetesimal formation I. Experimental study
• Accreting planets as dust dams in `transition' discs
• Inside-Out Planet Formation. III. Planet-disk interaction at the dead zone inner boundary
• Inner Super-Earths, Outer Gas Giants: How Pebble Isolation and Migration Feedback Keep Jupiters Cold
• Optically Thin Core Accretion: How Planets Get Their Gas in Nearly Gas-Free Disks
• Inside-Out Planet Formation. V. Structure of the Inner Disk as Implied by the MRI
• Inside-Out Planet Formation. IV. Pebble Evolution and Planet Formation Timescales

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