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Title: C/O ratios of stars with transiting hot Jupiter exoplanets ,

The relative abundances of carbon and oxygen have long been recognized as fundamental diagnostics of stellar chemical evolution. Now, the growing number of exoplanet observations enable estimation of these elements in exoplanetary atmospheres. In hot Jupiters, the C/O ratio affects the partitioning of carbon in the major observable molecules, making these elements diagnostic of temperature structure and composition. Here we present measurements of carbon and oxygen abundances in 16 stars that host transiting hot Jupiter exoplanets, and we compare our C/O ratios to those measured in larger samples of host stars, as well as those estimated for the corresponding exoplanet atmospheres. With standard stellar abundance analysis we derive stellar parameters as well as [C/H] and [O/H] from multiple abundance indicators, including synthesis fitting of the [O I] λ6300 line and non-LTE corrections for the O I triplet. Our results, in agreement with recent suggestions, indicate that previously measured exoplanet host star C/O ratios may have been overestimated. The mean transiting exoplanet host star C/O ratio from this sample is 0.54 (C/O{sub ☉} = 0.54), versus previously measured C/O{sub host} {sub star} means of ∼0.65-0.75. We also observe the increase in C/O with [Fe/H] expected for all stars based on Galacticmore » chemical evolution; a linear fit to our results falls slightly below that of other exoplanet host star studies but has a similar slope. Though the C/O ratios of even the most-observed exoplanets are still uncertain, the more precise abundance analysis possible right now for their host stars can help constrain these planets' formation environments and current compositions.« less
Authors:
;  [1] ;  [2] ;  [3] ;  [4]
  1. Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)
  2. National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States)
  3. University of Tampa, 401 West Kennedy Boulevard, Tampa, FL 33606 (United States)
  4. Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721 (United States)
Publication Date:
OSTI Identifier:
22356681
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 788; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; ATMOSPHERES; CARBON; COMPARATIVE EVALUATIONS; CONCENTRATION RATIO; CORRECTIONS; EVOLUTION; JUPITER PLANET; LTE; MOLECULES; OXYGEN; SATELLITES; STARS; SYNTHESIS