THE MASS–METALLICITY RELATION FOR GIANT PLANETS

By D. Thorngren, Jon Fortney, R. Murray-Clay, E. Lopez. 2015

176 citations recorded by the source corpus.

Exoplanet discoveries of recent years have provided a great deal of new data for studying the bulk compositions of giant planets. Here we identify 47 transiting giant planets (20 M⊕ < M < 20 MJ) whose stellar insolations are low enough (F* < 2 × 108 erg s−1 cm−2, or roughly Teff < 1000) that they are not affected by the hot-Jupiter radius inflation mechanism(s). We compute a set of new thermal and structural evolution models and use these models in comparison with properties of the 47 transiting planets (mass, radius, age) to determine their heavy element masses. A clear correlation emerges between the planetary heavy element mass Mz and the total planet mass, approximately of the form . This finding is consistent with the core-accretion model of planet formation. We also study how stellar metallicity [Fe/H] affects planetary metal-enrichment and find a weaker correlation than has previously been reported from studies with smaller sample sizes. We confirm a strong relationship between the planetary metal-enrichment relative to the parent star Zplanet/Zstar and the planetary mass, but see no relation in Zplanet/Zstar with planet orbital properties or stellar mass. The large heavy element masses of many planets (>50 M⊕) suggest significant amounts of heavy elements in H/He envelopes, rather than cores, such that metal-enriched giant planet atmospheres should be the rule. We also discuss a model of core-accretion planet formation in a one-dimensional disk and show that it agrees well with our derived relation between mass and Zplanet/Zstar.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/7f643a301ca410402ec0c4edb550dbab5a2f46e5

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In Astronomy and Astrophysics

Citations in the corpus

Pebble-isolation mass: Scaling law and implications for the formation of super-Earths and gas giants (2018, background): “…because even as the disc evolves and H/r decreases, the pebble isolation mass stays high enough so that the ice giants did not reach pebble isolation mass. Additionally, discs with higher viscosity can more easily match overall the heavy element content of giant exoplanets (Thorngren et al. 2016).”
Why do protoplanetary disks appear not massive enough to form the known exoplanet population? (2018, methodology): “For more massive planets, instead, we convert the planet mass into core masses using the relation found by Thorngren et al. (2016) using a sample of 47 transiting planets.”
The Complete Transmission Spectrum of WASP-39b with a Precise Water Constraint (2017, background): “Additionally, previous observations and theoretical models of extrasolar gas giant planets show that these planets may have metallicities greater than 1× solar (e.g. Kreidberg et al. 2014; Thorngren et al. 2016; Wakeford et al. 2017).”