A Survey for C II Emission-Line Stars in the Large Magellanic Cloud
  We present a narrow-band imaging survey of the Large Magellanic Cloud,
designed to isolate the C II $\lambda\lambda$7231, 7236 emission lines in
objects as faint as $m_{\lambda7400}\sim18$. The work is motivated by the
recent serendipitous discovery in the LMC of the first confirmed extragalactic
[WC11] star, whose spectrum is dominated by C II emission, and the realization
that the number of such objects is currently largely unconstrained. The survey,
which imaged $\sim$50$~$deg$^2$ using on-band and off-band filters, will
significantly increase the total census of these rare stars. In addition, each
new LMC [WC] star has a known luminosity, a quantity quite uncertain in the
Galactic sample. Multiple known C II emitters were easily recovered, validating
the survey design. We find 38 new C II emission candidates; spectroscopy of the
complete sample will be needed to ascertain their nature. In a preliminary
spectroscopic reconnaissance, we observed three candidates, finding C II
emission in each. One is a new [WC11]. Another shows both the narrow C II
emission lines characteristic of a [WC11], but also broad emission of C IV, O
V, and He II characteristic of a much hotter [WC4] star; we speculate that this
is a binary [WC]. The third object shows weak C II emission, but the spectrum
is dominated by a dense thicket of strong absorption lines, including numerous
O II transitions. We conclude it is likely an unusual hot, hydrogen-poor
post-AGB star, possibly in transition from [WC] to white dwarf. Even lacking a
complete spectroscopic program, we can infer that late [WC] stars do not
dominate the central stars of LMC planetary nebulae, and that the detected C II
emitters are largely of an old population.
