{
  "id": "astro-ph/0612562",
  "version": "v1",
  "published": "2006-12-19T21:47:40.000Z",
  "updated": "2006-12-19T21:47:40.000Z",
  "title": "The Energy Spectrum of the Blazar Markarian 421 Above 130 GeV",
  "authors": [
    "J. E. Carson",
    "J. Kildea",
    "R. A. Ong",
    "J. Ball",
    "D. A. Bramel",
    "C. E. Covault",
    "D. Driscoll",
    "P. Fortin",
    "D. M. Gingrich",
    "D. S. Hanna",
    "T. Lindner",
    "C. Mueller",
    "A. Jarvis",
    "R. Mukherjee",
    "K. Ragan",
    "R. A. Scalzo",
    "D. A. Williams",
    "J. Zweerink"
  ],
  "comment": "16 pages, 4 figures, submitted to ApJ",
  "journal": "Astrophys.J.662:199-204,2007",
  "doi": "10.1086/516818",
  "categories": [
    "astro-ph"
  ],
  "abstract": "Markarian 421 (Mrk 421) was the first blazar detected at gamma-ray energies above 300 GeV, and it remains one of only twelve TeV blazars detected to date. TeV gamma-ray measurements of its flaring activity and spectral variability have placed constraints on models of the high-energy emission from blazars. However, observations between 50 and 300 GeV are rare, and the high-energy peak of the spectral energy distribution (SED), predicted to be in this range, has never been directly detected. We present a detection of Mrk 421 above 100 GeV as made by the Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) during a multiwavelength campaign in early 2004. STACEE is a ground-based atmospheric Cherenkov telescope using the wavefront sampling technique to detect gamma rays at lower energies than achieved by most imaging Cherenkov telescopes. We also outline a method for reconstructing gamma-ray energies using a solar heliostat telescope. This technique was applied to the 2004 data, and we present the differential energy spectrum of Mrk 421 above 130 GeV. Assuming a differential photon flux dN/dE proportional to E^-a, we measure a spectral index a = 2.1 +/- 0.2 (statistical) +0.2/-0.1 (systematic). Finally, we discuss the STACEE spectrum in the context of the multiwavelength results from the same epoch.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2006-12-19T21:47:40.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "energy spectrum",
      "blazar markarian",
      "differential photon flux dn/de proportional",
      "tower atmospheric cherenkov effect experiment",
      "solar tower atmospheric cherenkov effect"
    ],
    "tags": [
      "journal article"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 16,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 735114
    }
  }
}