{
  "id": "1708.08337",
  "version": "v1",
  "published": "2017-08-28T14:35:37.000Z",
  "updated": "2017-08-28T14:35:37.000Z",
  "title": "Kinematics of OB-associations in Gaia epoch",
  "authors": [
    "A. M. Mel'nik",
    "A. K. Dambis"
  ],
  "comment": "19 pages, 10 figures, accepted for publication in MNRAS",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "We use stellar proper motions from the TGAS catalog to study the kinematics of OB-associations. The TGAS proper motions of OB-associations generally agree well with the Hipparcos proper motions. The parameters of the Galactic rotation curve obtained with TGAS and Hipparcos proper motions agree within the errors. The average one-dimensional velocity dispersion inside 18 OB-associations with more than 10 TGAS stars is sigma_v=3.9 km s-1, which is considerably smaller, by a factor of 0.4, than the velocity dispersions derived from Hipparcos data. The effective contribution from orbital motions of binary OB-stars into the velocity dispersion sigma_v inside OB-associations is sigma_b=1.2 km s-1. The median virial and stellar masses of OB-associations are equal to 7.1 10^5 and 9.0 10^3 Ms, respectively. Thus OB-associations must be unbound objects provided they do not include a lot of dense gas. The median star-formation efficiency is epsilon=2.1 percent. Nearly one third of stars of OB-associations must lie outside their tidal radius. We found that the Per OB1 and Car OB1 associations are expanding with the expansion started in a small region of 11--27 pc 7--10 Myr ago. The average expansion velocity is 6.3 km s-1.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2017-08-28T14:35:37.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "ob-associations",
      "gaia epoch",
      "kinematics",
      "average one-dimensional velocity dispersion inside",
      "hipparcos proper motions agree"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 19,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}