Forming rocky exoplanets around K-dwarf stars

Abstract

How multiple close-in super-Earths form around stars with masses lower than that of the Sun is still an open issue. Several recent modeling studies have focused on planet formation around M-dwarf stars, but so far no studies have focused specifically on K dwarfs, which are of particular interest in the search for extraterrestrial life. We aim to reproduce the currently known population of close-in super-Earths observed around K-dwarf stars and their system characteristics. We performed 48 high-resolution N-body simulations of planet formation via planetesimal accretion using the existing GENGA software running on GPUs. In the simulations we varied the initial disk mass and the solid and gas surface density profiles. Each simulation began with 12000 bodies with radii of between 200 and 2000 km around two different stars, with masses of 0.6 and 0.8 $M_{\odot }$. Most simulations ran for 20 Myr, with several simulations extended to 40 or 100 Myr. The mass distributions for the planets with masses between 2 and 12 $M_{\oplus }$ show a strong preference for planets with masses $M_p<6$ $M_{\oplus }$ and a lesser preference for planets with larger masses, whereas the mass distribution for the observed sample increases almost linearly. However, we managed to reproduce the main characteristics and architectures of the known planetary systems and produce mostly long-term angular-momentum-deficit-stable, nonresonant systems, but we require an initial disk mass of 15 $M_{\oplus }$ or higher and a gas surface density value at 1 AU of 1500 g cm${}^{-2}$ or higher. Our simulations also produce many low-mass planets with $M<2$ $M_{\oplus }$, which are not yet found in the observed population, probably due to the observational biases. The final systems contain only a small number of planets, which could possibly accrete substantial amounts of gas, and these formed after the gas had mostly dissipated.

27 pages, 29 figures, to be published in Astronomy & Astrophysics

References in corpus (34)

• Dynamical Outcomes of Planet-Planet Scattering
• The Occurrence and Mass Distribution of Close-in Super-Earths, Neptunes, and Jupiters
• The Solar Neighborhood XVII: Parallax Results from the CTIOPI 0.9m Program -- Twenty New Members of the RECONS 10 Parsec Sample
• Origins of Eccentric Extrasolar Planets: Testing the Planet-Planet Scattering Model
• A Steeper than Linear Disk Mass-Stellar Mass Scaling Relation
• Migration and the formation of systems of hot super-Earths and Neptunes
• A decreased probability of habitable planet formation around low-mass stars
• A Millimeter Continuum Size-Luminosity Relationship for Protoplanetary Disks
• Resonant Repulsion of Kepler Planet Pairs
• On the formation of planetary systems via oligarchic growth in thermally evolving viscous discs
• Kepler Multi-Planet Systems Exhibit Unexpected Intra-system Uniformity in Mass and Radius
• The Solar Neighborhood XXXV: Distances to 1404 M Dwarf Systems Within 25 pc in the Southern Sky
• Hot super-Earths and giant planet cores from different migration histories
• Chaotic diffusion in the Solar System
• AMD-stability and the classification of planetary systems
• Contemporary formation of early solar system planetesimals at two distinct radial locations
• Synthesizing Exoplanet Demographics from Radial Velocity and Microlensing Surveys, II: The Frequency of Planets Orbiting M Dwarfs
• A reassessment of the in situ formation of close-in super-Earths
• The GENGA Code: Gravitational Encounters in N-body simulations with GPU Acceleration
• Accounting for Incompleteness due to Transit Multiplicity in Kepler Planet Occurrence Rates
• The occurrence rate of giant planets orbiting low-mass stars with TESS
• Planetesimal Population Synthesis: Pebble Flux Regulated Planetesimal Formation
• Early Solar System instability triggered by dispersal of the gaseous disk
• CKS VIII: Eccentricities of Kepler Planets and Tentative Evidence of a High Metallicity Preference for Small Eccentric Planets
• Terrestrial Planet Formation in the Presence of Migrating Super-earths
• Magnetospheric Gap and Accumulation of Giant Planets Close to the Star
• Growing Mars fast: High-resolution GPU simulations of embryo formation
• A Criterion for the Stability of Planets in Chains of Resonances
• The terrestrial planet formation paradox inferred from high-resolution N-body simulations
• Earths in Other Solar Systems N-body simulations: the Role of Orbital Damping in Reproducing the Kepler Planetary Systems
• The origins of nearly coplanar, non-resonant systems of close-in super-Earths
• Long-term tidal evolution of the TRAPPIST-1 system
• Exoplanet Predictions Based on Harmonic Orbit Resonances
• Exoplanets Prediction in Multiplanetary Systems