{
  "id": "1003.2001",
  "version": "v1",
  "published": "2010-03-10T00:35:11.000Z",
  "updated": "2010-03-10T00:35:11.000Z",
  "title": "Discovery of a superluminal Fe K echo at the Galactic Center: The glorious past of Sgr A* preserved by molecular clouds",
  "authors": [
    "Gabriele Ponti",
    "Regis Terrier",
    "Andrea Goldwurm",
    "Guillaume Belanger",
    "Guillaume Trap"
  ],
  "comment": "ApJ in press 17 pages, 14 Figures, 3 tables",
  "categories": [
    "astro-ph.HE",
    "astro-ph.GA"
  ],
  "abstract": "We present the result of a study of the X-ray emission from the Galactic Centre (GC) Molecular Clouds (MC) within 15 arcmin from Sgr A*. We use XMM-Newton data (about 1.2 Ms of observation time) spanning about 8 years. The MC spectra show all the features characteristic of reflection: i) intense Fe Kalpha, with EW of about 0.7-1 keV, and the associated Kbeta line; ii) flat power law continuum and iii) a significant Fe K edge (tau~0.1-0.3). The diffuse low ionisation Fe K emission follows the MC distribution, nevertheless not all MC are Fe K emitters. The long baseline monitoring allows the characterisation of the temporal evolution of the MC emission. A complex pattern of variations is shown by the different MC, with some having constant Fe K emission, some increasing and some decreasing. In particular, we observe an apparent super-luminal motion of a light front illuminating a Molecular nebula. This might be due to a source outside the MC (such as Sgr A* or a bright and long outburst of a X-ray binary), while it cannot be due to low energy cosmic rays or a source located inside the cloud. We also observe a decrease of the X-ray emission from G0.11-0.11, behaviour similar to the one of Sgr B2. The line intensities, clouds dimensions, columns densities and positions with respect to Sgr A*, are consistent with being produced by the same Sgr A* flare. The required high luminosity (about 1.5~10^39 erg/s) can hardly be produced by a binary system, while it is in agreement with a flare of Sgr A* fading about 100 years ago. The low intensity of the Fe K emission coming from the 50 and the 20 km/s MC places an upper limit of 10^36 erg/s to the mean luminosity of Sgr A* in the last 60-90 years. The Fe K emission and variations from these MC might have been produced by a single flare of Sgr A*.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2010-03-10T00:35:11.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "molecular clouds",
      "galactic center",
      "superluminal fe",
      "glorious past",
      "x-ray emission"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1088/0004-637X/714/1/732",
      "journal": "The Astrophysical Journal",
      "year": 2010,
      "month": "May",
      "volume": 714,
      "number": 1,
      "pages": 732
    },
    "note": {
      "typesetting": "TeX",
      "pages": 17,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 848416,
      "adsabs": "2010ApJ...714..732P"
    }
  }
}