{
  "id": "1605.01043",
  "version": "v1",
  "published": "2016-05-03T19:44:50.000Z",
  "updated": "2016-05-03T19:44:50.000Z",
  "title": "Searches for Axion-Like Particles with NGC1275: Observation of Spectral Modulations",
  "authors": [
    "Marcus Berg",
    "Joseph P. Conlon",
    "Francesca Day",
    "Nicholas Jennings",
    "Sven Krippendorf",
    "Andrew J. Powell",
    "Markus Rummel"
  ],
  "comment": "37 pages, 17 figures",
  "categories": [
    "astro-ph.HE",
    "hep-ph"
  ],
  "abstract": "Axion-like particles (ALPs) can induce localised O(10%) oscillatory modulations in the spectra of photon sources passing through astrophysical magnetic fields. Ultra-deep Chandra observations of the Perseus cluster contain over $5 \\times 10^5$ counts from the central NGC1275 AGN and represent a dataset of extraordinary quality for ALP searches. We use these to search for X-ray spectral irregularities from the AGN. The absence of irregularities at the O(30%) level allows us to place leading constraints on the ALP-photon mixing parameter $g_{a\\gamma\\gamma} \\lesssim 1.5 - 5.4 \\times 10^{-12} {\\rm GeV}^{-1}$ for $m_a \\lesssim 10^{-12}$eV, depending on assumptions on the magnetic field realisation along the line of sight. At O(10%) level two modulations are present at high statistical significance, an excess in the 2-2.2 keV region and a deficit at 3.4-3.5 keV. We are unable to account for these through conventional instrumental or astrophysical processes and, interpreted as a signal, they would correspond to an ALP-photon coupling in the range $g_{a \\gamma \\gamma} \\sim 1-5 \\times 10^{-12} {\\rm GeV}^{-1}$.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2016-05-03T19:44:50.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "axion-like particles",
      "spectral modulations",
      "x-ray spectral irregularities",
      "magnetic field realisation",
      "central ngc1275 agn"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 37,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 1454386
    }
  }
}