Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Estimation of the Parameters of the Spiral Pattern in the Galaxy Based
  on a Sample of Classical Cepheids   We consider a sample of Galactic classical Cepheids with highly accurate
estimates of their distances taken from Skowron et al., where they were
determined based on the period-luminosity relation. We have refined the
geometric characteristics of two spiral arm segments-the Carina-Sagittarius and
Outer ones. For this purpose, we have selected 269 Cepheids belonging to the
Carina-Sagittarius arm with ages in the range 80-120 Myr. From them we have
estimated the pitch angle of the spiral pattern $i=-11.9\pm0.2^\circ$ and the
position of this arm $a_0=7.32\pm0.05$ kpc for the adopted $R_0=8.1\pm0.1$ kpc.
In the Outer arm we have selected 343 Cepheids with ages in the range 120-300
Myr. From them we have found $i=-11.5\pm0.5^\circ$ and $a_0=12.89\pm0.06$ kpc.
Adhering to the model of a grand-design spiral pattern in the Galaxy with one
pitch angle for all arms, we can conclude that this angle is close to
$-12^\circ$.

31
The categories of this paper are: ao-sci
2
The categories of this paper are: math
27
The categories of this paper are: comp-gas
16
The categories of this paper are: stat
14
The categories of this paper are: math-ph
3
The categories of this paper are: physics
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
24
The categories of this paper are: dg-ga
29
The categories of this paper are: funct-an
19
The categories of this paper are: eess
8
The categories of this paper are: hep-ex
15
The categories of this paper are: nucl-ex
1
The categories of this paper are: cs
22
The categories of this paper are: chao-dyn
5
The categories of this paper are: gr-qc