Orientation Parameters of the Cepheid System in the Galaxy

Vadim Bobylev

doi:10.1134/S1063773713110029

paper

Orientation Parameters of the Cepheid System in the Galaxy

arXiv:1310.7186 · doi:10.1134/S1063773713110029

Abstract

Based on the distribution of long-period Cepheids, we have redetermined the orientation parameters of their principal plane in the Galaxy. Based on 299 Cepheids with heliocentric distances $r < 20$ kpc and pulsation periods $P \geq 5^{d}$ , we have found the directions of the three principal axes of the position ellipsoid: $L_{1} = 281.0 \pm 0. 1^{\circ},$ $B_{1} = - 1.9 \pm 0. 1^{\circ},$ $L_{2} = 11.0 \pm 0. 7^{\circ},$ $B_{2} = 0.2 \pm 0. 1^{\circ}$ and $L_{3} = 275.9 \pm 0. 7^{\circ},$ $B_{3} = 88.1 \pm 0. 1^{\circ}$ . Thus, the line of nodes $l_{Ω} = L_{3} + 9 0^{\circ} = 5. 9^{\circ}$ is very close to the direction to the Galactic center; the Cepheid symmetry plane is inclined to the Galactic plane approximately by $- 2^{\circ}$ in the direction of the first axis ( $L_{1}$ ). The direction of the line of nodes found from old Cepheids ( $P < 5^{d}$ ) differs significantly and is $l_{Ω} = 29 8^{\circ}$ . The elevation of the Sun above the Galactic plane has been estimated from 365 closer stars ( $r < 4$ kpc) without any constraint on the pulsation period to be $h_{⊙} = 23 \pm 5$ pc.

10 pages, 3 figures

Orientation Parameters of the Cepheid System in the Galaxy

Abstract

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