Astrophys. J., 831, 64-64 (2016/November-1)
The mass-metallicity relation for giant planets.
THORNGREN D.P., FORTNEY J.J., MURRAY-CLAY R.A. and LOPEZ E.D.
Abstract (from CDS):
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 x 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 Mz∝\sqrtM. 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.
© 2016. The American Astronomical Society. All rights reserved.
planets and satellites: composition - planets and satellites: gaseous planets - planets and satellites: interiors - planets and satellites: physical evolution - planets and satellites: physical evolution
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