Very Large Excesses of 18 O in Hydrogen-deficient Carbon and R Coronae Borealis Stars: Evidence for White Dwarf Mergers

@article{Clayton2007VeryLE,
  title={Very Large Excesses of 18 O in Hydrogen-deficient Carbon and R Coronae Borealis Stars: Evidence for White Dwarf Mergers},
  author={G. Clayton and T. Geballe and F. Herwig and C. Fryer and M. Asplund},
  journal={The Astrophysical Journal},
  year={2007},
  volume={662},
  pages={1220-1230}
}
We have found that at least seven hydrogen-deficient carbon (HdC) and R Coronae Borealis (RCB) stars, have 16O/18O ratios close to and in some cases less than unity, values that are orders of magnitude lower than measured in other stars (the Solar value is 500). Greatly enhanced 18O is evident in every HdC and RCB we have measured that is cool enough to have detectable CO bands. The three HdC stars measured have 16O/18O < 1, lower values than any of the RCB stars. These discoveries are… Expand

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