Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the late spectral types of cataclysmic variable secondaries   We investigate why the spectral type of most cataclysmic variable (CV)
secondaries is significantly later than that of a ZAMS star with the same mean
density. Using improved stellar input physics, tested against observations of
low-mass stars at the bottom of the main sequence, we calculate the secular
evolution of CVs with low-mass donors. We consider sequences with different
mass transfer rates and with a different degree of nuclear evolution of the
donor prior to mass transfer. Systems near the upper edge of the gap ($P \sim 3
- 6$ h) can be reproduced by models with a wide range of mass transfer rates
from $1.5 \times 10^{-9} \msolyr$ to $10^{-8} \msolyr$. Evolutionary sequences
with a small transfer rate and donors that are substantially evolved off the
ZAMS (central hydrogen content $0.05-0.5$) reproduce CVs with late spectral
types above $P \simgr$ 6 h. Systems with the most discrepant (late) spectral
type should have the smallest donor mass at any given $P$. Consistency with the
period gap suggests that the mass transfer rate increases with decreasing donor
mass for evolved sequences above the period gap. In this case, a
single-parameter family of sequences with varying $\xc$ and increasing mass
transfer rate reproduces the full range of observed spectral types. This would
imply that CVs with such evolved secondaries dominate the CV population.

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The categories of this paper are: funct-an
25
The categories of this paper are: patt-sol
13
The categories of this paper are: quant-ph
23
The categories of this paper are: solv-int
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The categories of this paper are: q-fin
34
The categories of this paper are: chem-ph
22
The categories of this paper are: chao-dyn
1
The categories of this paper are: cs
8
The categories of this paper are: hep-ex
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The categories of this paper are: nucl-th
7
The categories of this paper are: hep-th
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The categories of this paper are: dg-ga
0
The categories of this paper are: hep-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: ao-sci
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The categories of this paper are: mtrl-th