{
  "id": "1503.03065",
  "version": "v1",
  "published": "2015-03-10T20:00:00.000Z",
  "updated": "2015-03-10T20:00:00.000Z",
  "title": "Ultracool White Dwarfs and the Age of the Galactic Disk",
  "authors": [
    "A. Gianninas",
    "B. Curd",
    "John R. Thorstensen",
    "Mukremin Kilic",
    "P. Bergeron",
    "Jeff J. Andrews",
    "Paul Canton",
    "M. A. Agüeros"
  ],
  "comment": "16 pages, 11 figures, 4 tables, accepted for publication in MNRAS",
  "categories": [
    "astro-ph.SR"
  ],
  "abstract": "We present parallax observations and a detailed model atmosphere analysis of 54 cool and ultracool ($T_{\\rm eff}$ < 4000 K) white dwarfs (WDs) in the solar neighborhood. For the first time, a large number of cool and ultracool WDs have distance and tangential velocities measurements available. Our targets have distances ranging from 21 pc to >100 pc, and include five stars within 30 pc. Contrary to expectations, all but two of them have tangential velocities smaller than 150 km s$^{-1}$ thus suggesting Galactic disk membership. The oldest WDs in this sample have WD cooling ages of 10 Gyr, providing a firm lower limit to the age of the thick disk population. Many of our targets have uncharacteristically large radii, indicating that they are low mass WDs. It appears that we have detected the brighter population of cool and ultracool WDs near the Sun. The fainter population of ultracool CO-core WDs remain to be discovered in large numbers. The Large Synoptic Survey Telescope should find these elusive, more massive ultracool WDs in the solar neighborhood.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2015-03-10T20:00:00.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "ultracool white dwarfs",
      "large synoptic survey telescope",
      "ultracool co-core wds remain",
      "ultracool wds",
      "tangential velocities smaller"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 16,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}