{
  "id": "1905.04330",
  "version": "v1",
  "published": "2019-05-10T18:22:13.000Z",
  "updated": "2019-05-10T18:22:13.000Z",
  "title": "Detection of Superluminal Motion in the X-ray Jet of M87",
  "authors": [
    "Bradford Snios",
    "Paul E. J. Nulsen",
    "Ralph P. Kraft",
    "C. C. Cheung",
    "Eileen T. Meyer",
    "William R. Forman",
    "Christine Jones",
    "Stephen S. Murray"
  ],
  "comment": "Accepted to ApJ, 12 pages, 4 figures, 4 tables",
  "categories": [
    "astro-ph.HE"
  ],
  "abstract": "Chandra HRC observations are investigated for evidence of proper motion and brightness changes in the X-ray jet of the nearby radio galaxy M87. Using images spanning 5 years, proper motion is measured in the X-ray knot HST-1, with a superluminal apparent speed of $6.3 \\pm 0.4 c$, or $24.1 \\pm 1.6\\rm\\ mas\\ yr^{-1}$, and in Knot D, with a speed of $2.4\\pm 0.6c$. Upper limits are placed on the speeds of the remaining jet features. The X-ray knot speeds are in excellent agreement with existing measurements in the radio, optical, and ultraviolet. Comparing the X-ray results with images from the Hubble Space Telescope indicates that the X-ray and optical/UV emitting regions co-move. The X-ray knots also vary by up to 73% in brightness, whereas there is no evidence of brightness changes in the optical/UV. Using the synchrotron cooling models, we determine lower limits on magnetic field strengths of $\\sim 420~\\mu \\rm G$ and $\\sim 230~\\mu \\rm G$ for HST-1 and Knot A, respectively, consistent with estimates of the equipartition fields. Together, these results lend strong support to the synchrotron cooling model for Knot HST-1, which requires that its superluminal motion reflects the speed of relativistic bulk flow in the jet.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2019-05-10T18:22:13.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "x-ray jet",
      "superluminal motion",
      "synchrotron cooling model",
      "nearby radio galaxy m87",
      "proper motion"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 12,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}