Constraining the entropy of formation from young transiting planets

Abstract

Recently K2 and TESS have discovered transiting planets with radii between $\sim$ 5-10 R${}_{\oplus }$ around stars with ages $<100$ Myr. These young planets are likely to be the progenitors of the ubiquitous super-earths/sub-neptunes, that are well studied around stars with ages $\gtrsim 1$ Gyr. The formation and early evolution of super-earths/sub-neptunes are poorly understood. Various planetary origin scenarios predict a wide range of possible formation entropies. We show how the formation entropies of young ($\sim$20-60 Myr), highly irradiated planets can be constrained if their mass, radius and age are measured. This method works by determining how low-mass a H/He envelope a planet can retain against mass-loss. This lower bound on the H/He envelope mass can then be converted into an upper bound on the entropy. If planet mass measurements with errors $\lesssim 20$\% can be achieved for the discovered young planets around DS Tuc A and V1298 Tau, then insights into their origins can be obtained. For these planets, higher measured planet masses would be consistent with standard core-accretion theory. In contrast, lower planet masses ($\lesssim 6-7$ M${}_{\oplus }$) would require a "boil-off" phase during protoplanetary disc dispersal to explain.

Accepted for publication in MNRAS

References in corpus (34)

• Modules for Experiments in Stellar Astrophysics (MESA)
• The Transiting Exoplanet Survey Satellite
• The K2 Mission: Characterization and Early results
• Mass-Radius Relationships for Solid Exoplanets
• Most 1.6 Earth-Radius Planets are not Rocky
• Atmospheric Escape from Hot Jupiters
• Growth Model Interpretation of Planet Size Distribution
• Planets and Stellar Activity: Hide and Seek in the CoRoT-7 system
• Planetary population synthesis coupled with atmospheric escape: a statistical view of evaporation
• Make Super-Earths, Not Jupiters: Accreting Nebular Gas onto Solid Cores at 0.1 AU and Beyond
• The Extreme Ultraviolet and X-Ray Sun in Time: High-Energy Evolutionary Tracks of a Solar-Like Star
• A planet within the debris disk around the pre-main-sequence star AU Microscopii
• A Sub-Neptune Exoplanet with a Low-Metallicity Methane-Depleted Atmosphere and Mie-Scattering Clouds
• Constraints on the mass of a habitable planet with water of nebular origin
• The Mass of Kepler-93b and The Composition of Terrestrial Planets
• Hydrodynamics of Embedded Planets' First Atmospheres. II. A Rapid Recycling of Atmospheric Gas
• The Gaia-Kepler Stellar Properties Catalog. II. Planet Radius Demographics as a Function of Stellar Mass and Age
• A Statistical Reconstruction of the Planet Population Around Kepler Solar-Type Stars
• Four newborn planets transiting the young solar analog V1298 Tau
• Planet formation with envelope enrichment: new insights on planetary diversity
• Aeronomical constraints to the minimum mass and maximum radius of hot low-mass planets
• TESS Hunt for Young and Maturing Exoplanets (THYME) II: A 17 Myr Old Transiting Hot Jupiter in the Sco-Cen Association
• Critical core mass for enriched envelopes: the role of H2O condensation
• A new class of Super-Earths formed from high-temperature condensates: HD219134 b, 55 Cnc e, WASP-47 e
• Accounting for Incompleteness due to Transit Multiplicity in Kepler Planet Occurrence Rates
• Testing exoplanet evaporation with multi-transiting systems
• The Boundary between Gas-rich and Gas-poor Planets
• Tidal Inflation Reconciles Low-Density Sub-Saturns with Core Accretion
• Star Spot Induced Radial Velocity Variability in LkCa 19
• The Preservation of Super Earths and the Emergence of Gas Giants after Their Progenitor Cores have Entered the Pebble Isolation Phase
• Ohmic Dissipation in Mini-Neptunes
• Close-in Super-Earths: The first and the last stages of planet formation in an MRI-accreting disc
• Tidal Heating of Young Super-Earth Atmospheres
• Formation of Planetary Populations III: Core Composition & Atmospheric Evaporation

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• A PSF-based Approach to TESS High quality data Of Stellar clusters (PATHOS) -- IV. Candidate exoplanets around stars in open clusters: frequency and age-planetary radius distribution
• How does the mass and activity history of the host star affect the population of low-mass planets?
• TESS Investigation -- Demographics of Young Exoplanets (TI-DYE) II: a second giant planet in the 17-Myr system HIP 67522
• A 38 Million Year Old Neptune-Sized Planet in the Kepler Field
• Updated Planetary Mass Constraints of the Young V1298 Tau System Using MAROON-X
• A young progenitor for the most common planetary systems in the Galaxy
• TOI-837 b: characterisation, formation and evolutionary history of an infant warm Saturn-mass planet
• Atmospheric mass loss and stellar wind effects in young and old systems II: Is TOI-942 the past of TOI-421 system?