{
  "id": "1208.4950",
  "version": "v1",
  "published": "2012-08-24T11:01:20.000Z",
  "updated": "2012-08-24T11:01:20.000Z",
  "title": "On the metallicity dependence of crystalline silicates in oxygen-rich asymptotic giant branch stars and red supergiants",
  "authors": [
    "O. C. Jones",
    "F. Kemper",
    "B. A. Sargent",
    "I. McDonald",
    "C. Gielen",
    "Paul M. Woods",
    "G. C. Sloan",
    "M. L. Boyer",
    "A. A. Zijlstra",
    "G. C. Clayton",
    "K. E. Kraemer",
    "S. Srinivasan",
    "P. M. E. Ruffle"
  ],
  "comment": "Accepted for publication in MNRAS, 24 pages, 16 figures",
  "categories": [
    "astro-ph.SR",
    "astro-ph.GA"
  ],
  "abstract": "We investigate the occurrence of crystalline silicates in oxygen-rich evolved stars across a range of metallicities and mass-loss rates. It has been suggested that the crystalline silicate feature strength increases with increasing mass-loss rate, implying a correlation between lattice structure and wind density. To test this, we analyse Spitzer IRS and Infrared Space Observatory SWS spectra of 217 oxygen-rich asymptotic giant branch stars and 98 red supergiants in the Milky Way, the Large and Small Magellanic Clouds and Galactic globular clusters. These encompass a range of spectral morphologies from the spectrally-rich which exhibit a wealth of crystalline and amorphous silicate features to 'naked' (dust-free) stars. We combine spectroscopic and photometric observations with the GRAMS grid of radiative transfer models to derive (dust) mass-loss rates and temperature. We then measure the strength of the crystalline silicate bands at 23, 28 and 33 microns. We detect crystalline silicates in stars with dust mass-loss rates which span over 3 dex, down to rates of ~10^-9 solar masses/year. Detections of crystalline silicates are more prevalent in higher mass-loss rate objects, though the highest mass-loss rate objects do not show the 23-micron feature, possibly due to the low temperature of the forsterite grains or it may indicate that the 23-micron band is going into absorption due to high column density. Furthermore, we detect a change in the crystalline silicate mineralogy with metallicity, with enstatite seen increasingly at low metallicity.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2012-08-24T11:01:20.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "oxygen-rich asymptotic giant branch stars",
      "crystalline silicate",
      "mass-loss rate",
      "red supergiants",
      "space observatory sws spectra"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1111/j.1365-2966.2012.21978.x",
      "journal": "Monthly Notices of the Royal Astronomical Society",
      "year": 2012,
      "month": "Dec",
      "volume": 427,
      "number": 4,
      "pages": 3209
    },
    "note": {
      "typesetting": "TeX",
      "pages": 24,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 1181742,
      "adsabs": "2012MNRAS.427.3209J"
    }
  }
}