Absolute densities in exoplanetary systems: photodynamical modelling of Kepler-138

Abstract

In favourable conditions, the density of transiting planets in multiple systems can be determined from photometry data alone. Dynamical information can be extracted from light curves, providing modelling is done self-consistently, i.e. using a photodynamical model, which simulates the individual photometric observations instead of the more generally used transit times. We apply this methodology to the Kepler-138 planetary system. The derived planetary bulk densities are a factor of 2 more precise than previous determinations, and we find a discrepancy in the stellar bulk density with respect to a previous study. This leads, in turn, to a discrepancy in the determination of masses and radii of the star and the planets. In particular, we find that interior planet, Kepler-138b, has a size in between Mars and the Earth. Given our mass and density estimates, we characterize the planetary interiors using a generalized Bayesian inference model. This model allows us to quantify for interior degeneracy and calculate confidence regions of interior parameters such as thicknesses of the core, the mantle, and ocean and gas layers. We find that Kepler-138b and Kepler-138d have significantly thick volatile layers and that the gas layer of Kepler-138b is likely enriched. On the other hand, Kepler-138c can be purely rocky.

accepted for publication in MNRAS

References in corpus (37)

• The Dartmouth Stellar Evolution Database
• 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
• DHP Framework: Digital Health Passports Using Blockchain -- Use case on international tourism during the COVID-19 pandemic
• Mass-Radius Relationships for Solid Exoplanets
• How to Constrain Your M Dwarf: measuring effective temperature, bolometric luminosity, mass, and radius
• On the radiative equilibrium of irradiated planetary atmospheres
• KEPLER's First Rocky Planet: Kepler-10b
• Measuring the rotation period distribution of field M-dwarfs with Kepler
• Planetary population synthesis coupled with atmospheric escape: a statistical view of evaporation
• Can we constrain interior structure of rocky exoplanets from mass and radius measurements?
• A spin-down clock for cool stars from observations of a 2.5-billion-year-old cluster
• Limb darkening and exoplanets: testing stellar model atmospheres and identifying biases in transit parameters
• Patterns of photometric and chromospheric variation among Sun-like stars: A 20-year perspective
• Alignment of the stellar spin with the orbits of a three-planet system
• A generalized bayesian inference method for constraining the interiors of super Earths and sub-Neptunes
• PASTIS: Bayesian extrasolar planet validation. I. General framework, models, and performance
• Heat transport in giant (exo)planets: a new perspective
• Magnetic activity in the HARPS M-dwarf sample. The rotation-activity relationship for very low-mass stars through R'HK
• Absolute properties of the low-mass eclipsing binary CM Draconis
• The effect of activity on stellar temperatures and radii
• Photometric Amplitude Distribution of Stellar Rotation of Kepler KOIs-Indication for Spin-Orbit Alignment of Cool Stars and High Obliquity for Hot Stars
• First Results from the CHARA Array. IV. The Interferometric Radii of Low-Mass Stars
• Homogeneous studies of transiting extrasolar planets. II. Physical properties
• The effect of stellar limb darkening values on the accuracy of the planet radii derived from photometric transit observations
• The mass of the Mars-sized exoplanet Kepler-138 b from transit timing
• Using long-term transit timing to detect terrestrial planets
• Determination of Three-dimensional Spin-orbit Angle with Joint Analysis of Asteroseismology, Transit Lightcurve, and the Rossiter-McLaughlin Effect: Cases of HAT-P-7 and Kepler-25
• An empirical calibration to estimate cool dwarf fundamental parameters from H-band spectra
• Three's Company: An additional non-transiting super-Earth in the bright HD 3167 system, and masses for all three planets
• Bayesian analysis of interiors of HD 219134b, Kepler-10b, Kepler-93b, CoRoT-7b, 55 Cnc e, and HD 97658b using stellar abundance proxies
• Revisiting the transits of CoRoT-7b at a lower activity level
• Chemical Abundances of M-dwarfs from the APOGEE Survey. I. The Exoplanet Hosting Stars Kepler-138 and Kepler-186
• Characterizing the Cool KOIs. VI. H- and K-band Spectra of Kepler M Dwarf Planet-Candidate Hosts
• A Low-Mass Exoplanet Candidate Detected By $K2$ Transiting the Praesepe M Dwarf JS 183
• M dwarf luminosity, radius, and $\alpha$-enrichment from $I$-band spectral features
• Magnetic activity in the photosphere of CoRoT-Exo-2a. Active longitudes and short-term spot cycle in a young Sun-like star

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