The Physical Parameters of Four WC-type Wolf-Rayet Stars in the Large
  Magellanic Cloud: Evidence of Evolution
  We present a spectral analysis of four LMC WC-type Wolf-Rayet (WR) stars
(BAT99-8, BAT99-9, BAT99-11, and BAT99-52) to shed light on two evolutionary
questions surrounding massive stars. The first is: are WO-type WR stars more
oxygen enriched than the WC-type stars, indicating further chemical evolution,
or are the strong high-excitation oxygen lines in the WO-type stars an
indication of higher temperatures. This study will act as a baseline for
answering the question of where WO-type stars fall in WR evolution. Each star's
spectrum, extending from 1100~\AA\ to 25000~\AA, was modeled using \cmfgen\ to
determine the star's physical properties such as luminosity, mass-loss rate,
and chemical abundances. The oxygen abundance is a key evolutionary diagnostic,
and with higher resolution data and an improved stellar atmosphere code, we
found the oxygen abundance to be up to a factor of 5 lower than previous
studies. The second evolutionary question revolves around the formation of WR
stars: Do they evolve by themselves or is a close companion star necessary for
their formation? Using our derived physical parameters, we compared our results
to the Geneva single-star evolutionary models and the BPASS binary evolutionary
models. We found that both the Geneva solar metallicity models and BPASS LMC
metallicity models are in agreement with the four WC-type stars, while the
Geneva LMC metallicity models are not. Therefore, these four WC4 stars could
have been formed either via binary or single-star evolution.
