Estimation of the Parameters of the Spiral Pattern in the Galaxy Based on a Sample of Classical Cepheids. (arXiv:2204.06398v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Bobylev_V/0/1/0/all/0/1">V. V. Bobylev</a>

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 $i=-11.9pm0.2^circ$ and the
position of this arm $a_0=7.32pm0.05$ kpc for the adopted $R_0=8.1pm0.1$ kpc.
In the Outer arm we have selected 343 Cepheids with ages in the range 120-300
Myr. From them we have found $i=-11.5pm0.5^circ$ and $a_0=12.89pm0.06$ 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
$-12^circ$.

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 $i=-11.9pm0.2^circ$ and the
position of this arm $a_0=7.32pm0.05$ kpc for the adopted $R_0=8.1pm0.1$ kpc.
In the Outer arm we have selected 343 Cepheids with ages in the range 120-300
Myr. From them we have found $i=-11.5pm0.5^circ$ and $a_0=12.89pm0.06$ 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
$-12^circ$.

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