Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Concerning the Slope of the Cepheid Period-Luminosity Relation   We discuss the impact of possible differences in the slope of the Cepheid
Period-Luminosity relation on the determination of extragalactic distances in
the context of recent studies that suggest changes in this slope. We show that
the Wesenheit function W = V - R x ((V-I), widely used for the determination of
Cepheid distances, is expected to be highly insensitive to changes in the slope
of the underlying (monochromatic) Period-Luminosity (PL) relations. This occurs
because the reddening trajectories in the color-magnitude plane are closely
parallel to lines of constant period. As a result W-based Period-Luminosity
relations have extremely low residual dispersion, which is because differential
(and total line-of-sight) reddening is eliminated in the definition of W and
the residual scatter due to a star's intrinsic color/position within the
Cepheid is also largely insensitive to W. Basic equations are presented and
graphically illustrated, showing the insensitivity of W to changes in the
monochromatic PL relations.

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The categories of this paper are: comp-gas
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The categories of this paper are: q-alg
9
The categories of this paper are: nlin
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The categories of this paper are: bayes-an
2
The categories of this paper are: math
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The categories of this paper are: funct-an
8
The categories of this paper are: hep-ex
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The categories of this paper are: hep-th
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The categories of this paper are: ao-sci
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The categories of this paper are: dg-ga
3
The categories of this paper are: physics
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The categories of this paper are: atom-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: adap-org
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The categories of this paper are: patt-sol
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The categories of this paper are: chao-dyn