{
  "id": "2211.07617",
  "version": "v1",
  "published": "2022-11-14T18:36:23.000Z",
  "updated": "2022-11-14T18:36:23.000Z",
  "title": "Limits on Leptonic TeV Emission from the Cygnus Cocoon with Swift-XRT",
  "authors": [
    "David Guevel",
    "Andrew Beardmore",
    "Kim L Page",
    "Amy Lien",
    "Ke Fang",
    "Luigi Tibaldo",
    "Sabrina Casanova",
    "Petra Huentemeyer"
  ],
  "comment": "9 pages, 5 figures",
  "categories": [
    "astro-ph.HE"
  ],
  "abstract": "$\\gamma$-ray observations of the Cygnus Cocoon, an extended source surrounding the Cygnus X star-forming region, suggest the presence of a cosmic ray accelerator reaching energies up to a few PeV. The very-high-energy (VHE; 0.1-100~TeV) $\\gamma$-ray emission may be explained by the interaction of cosmic-ray hadrons with matter inside the Cocoon, but an origin of inverse Compton radiation by relativistic electrons cannot be ruled out. Inverse Compton $\\gamma$-rays at VHE are accompanied by synchrotron radiation peaked in X-rays. Hence, X-ray observations may probe the electron population and magnetic field of the source. We observed eleven fields in or near the Cygnus Cocoon with the Neil Gehrels Swift Observatory's X-Ray Telescope (Swift-XRT) totaling 110 ksec. We fit the fields to a Galactic and extra-galactic background model and performed a log-likelihood ratio test for an additional diffuse component. We found no significant additional emission and established upper limits in each field. By assuming that the X-ray intensity traces the TeV intensity and follows an $dN/dE\\propto E^{-2.5}$ spectrum, we obtained a 90\\% upper limit of $F_X < 8.7\\times 10^{-11}\\rm~erg\\,cm^{-2}\\,s^{-1}$ or $< 5.2\\times 10^{-11}\\rm~erg\\,cm^{-2}\\,s^{-1}$ on the X-ray flux of the entire Cygnus Cocoon between 2 and 10 keV depending on the choice of hydrogen column density model. This suggests that no more than one quarter of the $\\gamma$-ray flux at 1 TeV is produced by inverse Compton scattering, when assuming an equipartition magnetic field of $\\sim 20\\,\\mu$G.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2022-11-14T18:36:23.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "cygnus cocoon",
      "leptonic tev emission",
      "ray accelerator reaching energies",
      "inverse compton",
      "gehrels swift observatorys x-ray telescope"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 9,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}