{
  "id": "1306.5642",
  "version": "v2",
  "published": "2013-06-24T14:31:39.000Z",
  "updated": "2013-07-03T21:05:35.000Z",
  "title": "Gamma-ray emission from the Westerlund 1 region",
  "authors": [
    "S. Ohm",
    "J. A. Hinton",
    "R. White"
  ],
  "comment": "accepted for publication in MNRAS, 6 pages, 4 figures, 2 tables",
  "categories": [
    "astro-ph.HE",
    "astro-ph.GA"
  ],
  "abstract": "Westerlund 1 (Wd 1) is the most massive stellar cluster in the Galaxy and associated with an extended region of TeV emission. Here we report the results of a search for GeV gamma-ray emission in this region. The analysis is based on ~4.5 years of Fermi-LAT data and reveals significantly extended emission which we model as a Gaussian, resulting in a best-fit sigma of sigma_S = (0.475 +/- 0.05) deg and an offset from Wd 1 of ~1 deg. A partial overlap of the GeV emission with the TeV signal as reported by H.E.S.S. is found. We investigate the spectral and morphological characteristics of the gamma-ray emission and discuss its origin in the context of two distinct scenarios. Acceleration of electrons in a Pulsar Wind Nebula provides a reasonably natural interpretation of the GeV emission, but leaves the TeV emission unexplained. A scenario in which protons are accelerated in or near Wd 1 in supernova explosion(s) and are diffusing away and interacting with molecular material, seems consistent with the observed GeV and TeV emission, but requires a very high energy input in protons, ~10^51 erg, and rather slow diffusion. Observations of Wd 1 with a future gamma-ray detector such as CTA provide a very promising route to fully resolve the origin of the TeV and GeV emission in Wd 1 and provide a deeper understanding of the high-energy (HE) astrophysics of massive stellar clusters.",
  "revisions": [
    {
      "version": "v2",
      "updated": "2013-07-03T21:05:35.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "tev emission",
      "gev emission",
      "westerlund",
      "massive stellar cluster",
      "gev gamma-ray emission"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1093/mnras/stt1170",
      "journal": "Monthly Notices of the Royal Astronomical Society",
      "year": 2013,
      "month": "Sep",
      "volume": 434,
      "number": 3,
      "pages": 2289
    },
    "note": {
      "typesetting": "TeX",
      "pages": 6,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 1239614,
      "adsabs": "2013MNRAS.434.2289O"
    }
  }
}