Abstract

It is currently unknown how/to what extent the chemical compositions of planetary atmospheres correlate with those of their host stars and/or if different host star compositions influence planet occurrence (beyond the well-known metallicity correlation). The carbon-to-oxygen abundance ratio is one crucial measurement that may be used to better understand a possible connection between star and planet compositions. Currently C and O are the only elements that can potentially be measured in both star and exoplanet atmospheres. Large samples of coupled planet and host star C/O measurements may reveal trends indicative of processes in the protoplanetary disk or planetary interior that shift the planet's elemental composition away from the star's. However, estimating C/O ratios in transiting exoplanet atmospheres is still difficult due to paucity of data and degeneracies between atmospheric model parameters. Moreover, even with high resolution, high S/N spectra, determinations of the stellar C/O ratios can be challenging. I will present a methodologically consistent sample of C/O ratios measured from high-resolution spectra of transiting exoplanet host stars from several different C and O abundance indicators, using classical stellar abundance analysis techniques. Additional elements measured from the transiting HJ host star sample, including other “planet-building” elements like Si and Mg, will also be presented. This talk will consider the difficulties of host star abundance measurements, and what insights into planet formation and composition are possible from such analyses. I will conclude with a preview of a new extension of the investigation of giant exoplanet compositions via comparison of bulk interior models and host star abundances.

Presentation

Talk slides - PDF