{
  "id": "1601.03507",
  "version": "v1",
  "published": "2016-01-14T07:27:26.000Z",
  "updated": "2016-01-14T07:27:26.000Z",
  "title": "Hot Subdwarf Stars Observed in LAMOST DR1 - Atmospheric parameters from single-lined spectra",
  "authors": [
    "Yangping Luo",
    "Peter Nemeth",
    "Chao Liu",
    "Licai Deng",
    "Zhanwen Han"
  ],
  "comment": "Accepted To The Astrophysical Journal",
  "categories": [
    "astro-ph.SR"
  ],
  "abstract": "We present a catalog of 166 spectroscopically identified hot subdwarf stars from LAMOST DR1, 44 of which show the characteristics of cool companions in their optical spectra. Atmospheric parameters of 122 non-composite spectra subdwarf stars were measured by fitting the profiles of hydrogen (H) and helium (He) lines with synthetic spectra from non-LTE model atmospheres. Most of the sdB stars scatter near the Extreme Horizontal Branch in the $T_{\\rm eff}-\\log{g}$ diagram and two well defined groups can be outlined. A clustering of He-enriched sdO stars appears near $T_{\\rm eff}=45\\,000$ K and $\\log(g) = 5.8$. The sdB population separates into several nearly parallel sequences in the $T_{\\rm eff}-{\\rm He}$ abundance diagram with clumps corresponding to those in the $T_{\\rm eff}-\\log{g}$ diagram. Over $38\\,000$ K (sdO) stars show abundance extremes, they are either He-rich or He-deficient and we observe only a few stars in the $ -1 < \\log(y) < 0$ abundance range. With increasing temperature these extremes become less prominent and the He abundance approaches to $\\log(y)\\sim-0.5$. A unique property of our sample is that it covers a large range in apparent magnitudes and galactic latitudes, therefore it contains a mix of stars from different populations and galactic environments. Our results are consistent with the findings of Hirsch (2009) and we conclude that He-rich and He-deficient sdB stars ($\\log(y) < 1$) probably origin from different populations. We also find that most sdO and sdB stars lie in a narrow strip in the luminosity and helium abundance plane, which suggests that these atmospheric parameters are correlated.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2016-01-14T07:27:26.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "atmospheric parameters",
      "lamost dr1",
      "identified hot subdwarf stars",
      "single-lined spectra",
      "sdb stars"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}