{
  "id": "2001.02486",
  "version": "v1",
  "published": "2020-01-08T12:58:59.000Z",
  "updated": "2020-01-08T12:58:59.000Z",
  "title": "Evidence for Galactic disc RR~Lyrae stars in the Solar neighbourhood",
  "authors": [
    "Z. Prudil",
    "I. Dékány",
    "E. K. Grebel",
    "A. Kunder"
  ],
  "comment": "12 pages, 9 figures",
  "categories": [
    "astro-ph.SR",
    "astro-ph.GA"
  ],
  "abstract": "We present a kinematical study of 314 RR~Lyrae stars in the solar neighbourhood using the publicly available photometric, spectroscopic, and {\\it Gaia} DR2 astrometric data to explore their distribution in the Milky Way. We report an overdensity of 22 RR~Lyrae stars in the solar neighbourhood at a pericenter distance of between 5--9\\,kpc from the Galactic center. Their orbital parameters and their chemistry indicate that these 22 variables share the kinematics and the [Fe/H] values of the Galactic disc, with an average metallicity and tangential velocity of [Fe/H]=$-0.60$\\,dex and $v_{\\theta} = 241$\\,km\\,s$^{-1}$, respectively. From the distribution of the Galactocentric spherical velocity components, we find that these 22 disc-like RR~Lyrae variables are not consistent with the {\\it Gaia} Sausage ({\\it Gaia}-Enceladus), unlike almost half of the local RR~Lyrae stars. Chemical information from the literature shows that the majority of the selected pericenter peak RR~Lyrae variables are $\\alpha$-poor, a property shared by typically much younger stars in the thin disc. Using the available photometry we rule out a possible misclassification with the known classical and anomalous Cepheids. The similar kinematic, chemical, and pulsation properties of these disc RR~Lyrae stars suggest they share a common origin. In contrast, we find the RR~Lyrae stars associated with the {\\it Gaia}-Enceladus based on their kinematics and chemical composition show a considerable metallicity spread in the old population ($\\sim$~1\\,dex).",
  "revisions": [
    {
      "version": "v1",
      "updated": "2020-01-08T12:58:59.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "solar neighbourhood",
      "galactic disc",
      "galactocentric spherical velocity components",
      "dr2 astrometric data",
      "pulsation properties"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 12,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}