{
  "id": "0906.5222",
  "version": "v1",
  "published": "2009-06-29T08:41:21.000Z",
  "updated": "2009-06-29T08:41:21.000Z",
  "title": "Hard X-ray flux from low-mass stars in the Cygnus OB2 Association",
  "authors": [
    "M. Caramazza",
    "J. J. Drake",
    "G. Micela",
    "E. Flaccomio"
  ],
  "comment": "5 pages",
  "categories": [
    "astro-ph.HE"
  ],
  "abstract": "Context. The Cygnus OB2 association, the central engine of the Cygnus X star-forming region, is the subject of an extensive INTEGRAL Key Project that will accumulate 6Ms of observations. Analysis of 2Ms of observations by De Becker and co-workers provides the most sensitive limit yet obtained on hard X-ray emission from the cluster. Aims. We investigate the X-ray emission in the 20-40 keV band expected from the flaring low-mass stellar population in Cygnus OB2. We discuss whether such emission needs to be considered in the interpretation of existing and future X-ray observations of the region, and whether such observations might provide insight into the high-energy processes on low-mass pre-main sequence stars. Methods. The total hard X-ray flux from low-mass stars is estimated by assuming the observed soft X-ray emission stems from a superposition of flares. We further assume the ratio of hard X-ray to soft X-ray emission is described by a scaling found for solar flares by Isola and co-workers. Results. We estimate the low-mass stellar hard X-ray flux in the 20-40 keV band to lie in the range ~2x10^31-6x10^32 erg/s and discuss some potential biases that might affect this result. Conclusions. Hard X-ray emission could lie at a level not much below the current observed flux upper limits for Cygnus OB2. If this emission could be detected, it would provide insight into the hard X-ray production of large flares on pre-main sequence stars. We highlight the penetrating power of hard X-rays from low-mass stellar populations as a possible pointer to our Galaxy's hidden star-forming clusters and super-clusters using more sensitive observations from future missions.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2009-06-29T08:41:21.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "cygnus ob2 association",
      "low-mass stars",
      "pre-main sequence stars",
      "low-mass stellar population",
      "hard x-ray emission"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1051/0004-6361/200811342",
      "journal": "Astronomy and Astrophysics",
      "year": 2009,
      "month": "Aug",
      "volume": 503,
      "number": 2,
      "pages": 505
    },
    "note": {
      "typesetting": "TeX",
      "pages": 5,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 824298,
      "adsabs": "2009A&A...503..505C"
    }
  }
}