{
  "id": "astro-ph/0210572",
  "version": "v1",
  "published": "2002-10-25T17:04:46.000Z",
  "updated": "2002-10-25T17:04:46.000Z",
  "title": "Far Ultraviolet Spectra of a Non-Radiative Shock Wave in the Cygnus Loop",
  "authors": [
    "John Raymond",
    "Parviz Ghavamian",
    "Ravi Sankrit",
    "William Blair",
    "Salvador Curiel"
  ],
  "comment": "To appear in Astrophysical Journal, Vol. 584, Feb. 20 2003",
  "journal": "Astrophys.J. 584 (2003) 770-781",
  "doi": "10.1086/345741",
  "categories": [
    "astro-ph"
  ],
  "abstract": "Spatial and spectral profiles of O VI emission behind a shock wave on the northern edge of the Cygnus Loop were obtained with the FUSE satellite. The velocity width of the narrowest O VI profile places a tight constraint on the electron-ion and ion-ion thermal equilibration in this 350 $\\rm km s^{-1}$ collisionless shock. Unlike faster shocks in SN1006 and in the heliosphere, this shock brings oxygen ions and protons to within a factor of 2.5 of the same temperature. Comparison with other shocks suggests that shock speed, rather than Alfv\\'{e}n Mach number, may control the degree of thermal equilibration. We combine the O VI observations with a low resolution far UV spectrum from HUT, an H$\\alpha$ image and ROSAT PSPC X-ray data to constrain the pre-shock density and the structure along the line-of-sight. As part of this effort, we model the effects of resonance scattering of O VI photons within the shocked gas and compute time-dependent ionization models of the X-ray emissivity. Resonance scattering affects the O VI intensities at the factor of 2 level, and the soft spectrum of the X-ray rim can be mostly attributed to departures from ionization equilibrium. The pre-shock density is about twice the canonical value for the Cygnus Loop X-ray emitting shocks.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2002-10-25T17:04:46.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "cygnus loop",
      "far ultraviolet spectra",
      "non-radiative shock wave",
      "loop x-ray emitting shocks",
      "low resolution far uv spectrum"
    ],
    "tags": [
      "journal article"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 600602
    }
  }
}