Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hipparcos Parallaxes and Proper Motions of Cepheids and their
  Implications   A summary is given of an analysis of the Hipparcos trigonometrical parallaxes
and proper motions of classical Cepheids. It is possible for the first time to
derive zero-points for the period-luminosity and period-luminosity-colour
relations from parallaxes alone, avoiding the problems of less direct methods.
The results imply an increase of 8 to 10 percent in the extragalactic distance
scale based on Cepheids. The proper motions are used to derive the constants of
galactic rotation. Comparison with radial velocity data leads to a confirmation
of the Cepheid distance scale derived from the parallaxes and indicates a
kinematic distance to the galactic centre of 8.5 +/- 0.5 kpc. From the new
Cepheid distances to the LMC and M31, the absolute magnitude of RR Lyrae
variables in metal-poor globular clusters is derived. Applying this to data on
metal-poor clusters in our own Galaxy leads to an age of about 11 Gyr for these
clusters, considerably less than previously thought. Other evidence from
Hipparcos on these matters is briefly reviewed and it is suggested that the
Cepheid results currently provide the most reliable scale on which to base
distances and ages.

15
The categories of this paper are: nucl-ex
18
The categories of this paper are: econ
27
The categories of this paper are: comp-gas
24
The categories of this paper are: dg-ga
1
The categories of this paper are: cs
7
The categories of this paper are: hep-th
34
The categories of this paper are: chem-ph
22
The categories of this paper are: chao-dyn
28
The categories of this paper are: alg-geom
26
The categories of this paper are: bayes-an
10
The categories of this paper are: q-bio
30
The categories of this paper are: q-alg
0
The categories of this paper are: hep-ph
3
The categories of this paper are: physics
23
The categories of this paper are: solv-int
33
The categories of this paper are: plasm-ph