Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: QU Car: a very high luminosity nova-like binary with a carbon-enriched
  companion   QU Car is listed in cataclysmic variable star catalogues as a nova-like
variable. This little-studied, yet bright interacting binary is re-appraised
here in the light of new high-quality ultraviolet (UV) interstellar line data
obtained with STIS on board the Hubble Space Telescope. The detection of a
component of interstellar absorption at a mean LSR velocity of $-$14 km
s$^{-1}$ indicates that the distance to QU Car may be $\sim$2 kpc or more -- a
considerable increase on the previous lower-limiting distance of 500 pc. If so,
the bolometric luminosity of QU Car could exceed $10^{37}$ ergs s$^{-1}$. This
would place this binary in the luminosity domain occupied by known
compact-binary supersoft X-ray sources. Even at a 500 pc, QU Car appears to be
the most luminous nova-like variable known.
  New intermediate dispersion optical spectroscopy of QU Car spanning
3800--7000 \AA is presented. These data yield the discovery that C{\sc iv}
$\lambda\lambda$5801,12 is present as an unusually prominent emission line in
an otherwise low-contrast line spectrum. Using measurements of this and other
lines in a recombination line analysis, it is shown that the C/He abundance as
proxied by the n(C$^{4+}$)/n(He$^{2+}$) ratio may be as high as 0.06 (an order
of magnitude higher than the solar ratio). Furthermore, the C/O abundance ratio
is estimated to be greater than 1. These findings suggest that the companion in
QU Car is a carbon star. If so, it would be the first example of a carbon star
in such a binary. An early-type R star best matches the required abundance
pattern and could escape detection at optical wavelengths provided the distance
to QU Car is $\sim$2 kpc or more.

0
The categories of this paper are: hep-ph
5
The categories of this paper are: gr-qc
4
The categories of this paper are: cond-mat
25
The categories of this paper are: patt-sol
32
The categories of this paper are: atom-ph
13
The categories of this paper are: quant-ph
36
The categories of this paper are: cmp-lg
3
The categories of this paper are: physics
8
The categories of this paper are: hep-ex
11
The categories of this paper are: hep-lat
35
The categories of this paper are: mtrl-th
17
The categories of this paper are: q-fin
29
The categories of this paper are: funct-an
14
The categories of this paper are: math-ph
2
The categories of this paper are: math
21
The categories of this paper are: adap-org