On the Motion of Stars in the Pleiades According to Gaia DR2 Data

• Published in: Astrophysical Bulletin
• Main Authors: Danilov, V. M., Seleznev, A. F.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Pleiades journals 2020
• Subjects: OPEN CLUSTERS AND ASSOCIATIONS; STARS: KINEMATICS AND DYNAMICS; North Pole
• Online Access: http://elar.urfu.ru/handle/10995/103164; https://www.scopus.com/inward/record.uri?eid=2-s2.0-85099386165&doi=10.1134%2fS1990341320040045&partnerID=40&md5=39522a9f2a5a0862636314110bf57a2e; http://arxiv.org/pdf/2012.15289; https://doi.org/10.1134/S1990341320040045

Abstract—Several parameters of the Pleiades cluster were estimated. We used Gaia DR2 data on the coordinates, proper motions, and radial velocities of stars in regions with radius d° =2.5° and size 60° × 60° around the cluster center. Based on data on stars with magnitudes mG ≤ 18m, we constructed a map and profile of the density, luminosity and mass functions of the cluster, determined the cluster radius, 10.9° ± 0.3° (26.3 ± 0.7 pc), and the radius of its core, 2.62° (6.24 pc), and obtained estimates for the number of stars in the cluster, 1542 ± 121, and their mass, 855 ± 104M⊙; numbers of stars in the core of the cluster, 1097 ± 77, and their mass 665 ± 71M⊙. Distribution of stars with mG< 16m at distances rs from the cluster center in three-dimensional space of rs< 1 pc and at rs ∼ 1.4–5 pc contains radial density waves. Based on the data on stars with mG< 16m, we determined the average rotation velocity of the core of the cluster vc = 0.56 ± 0.07 km s−1 at distances d in the sky plane d ≤ 4.6 pc from its center. The rotation is “prograde”, the angle between the projection of the axis of rotation of the cluster core onto the sky plane and the direction to the North Pole of the Galaxy is ϕ = 18.8° ± 4.4°, the angle between the axis of rotation of the cluster core and the sky plane is ϑ = 43.2° ± 4.9°, the rotation velocity of the cluster core at a distance of d ≃ 5.5pc from its center is close to zero: vc = 0.1 ± 0.3 km s−1. According to the data on stars with mG< 17m, the velocity of the “retrograde” rotation of the cluster at a distance of d ≃ 7.1 pc from its center is vc = 0.48 ± 0.20 km s−1, the angle ϕ = 37.8° ± 26.4°. The dependences of moduli of the tangential and radial components of the velocity field of the stars of the cluster core in the sky plane on the distance d to the center of the cluster contain a number of periodic oscillations. The dispersions of the velocities of the stars in the cluster core σv increase on average with an increase in rs, which, like the radial density waves ...