Effects of Mg/Si on Exoplanetary Refractory Oxygen Budget

TL;DR

This paper introduces ArCCoS, an open-source tool to model how stellar refractory element variations influence exoplanetary oxygen budgets, aiding interpretation of exoplanet structures.

Contribution

The paper presents ArCCoS, a novel open-source calculator that assesses how stellar Mg and Si abundances affect planetary oxygen and composition.

Findings

Variations in Mg/Si significantly impact oxygen condensation.

ArCCoS enables better interpretation of exoplanet interior structures.

Model provides observational tests for planetary composition theories.

Abstract

Solar photospheric abundances of refractory elements mirror the Earth's to within ~10 mol% when normalized to the dominant terrestrial planet-forming elements Mg, Si and Fe. This allows for the adoption of Solar composition as an order-of-magnitude proxy for Earth's. It is not known, however, the degree to which this mirroring of stellar and terrestrial planet abundances holds true for other star-planet systems without determination of the composition of initial planetesimals via condensation sequence calculations and post condensation processes. We present the open-source Arbitrary Composition Condensation Sequence calculator (ArCCoS) to assess how the elemental composition of a parent star affects that of the planet-building material, including the extent of oxidation within the planetesimals. We demonstrate the utility of ArCCoS by showing how variations in the abundance of the stellar refractory elements Mg and Si affect the condensation of oxygen, a controlling factor in the relative proportions of planetary core and silicate mantle material. This, thereby, removes significant degeneracy in the interpretation of the structures of exoplanets as well as providing observational tests for the validity of this model.