{
  "id": "0707.4478",
  "version": "v3",
  "published": "2007-07-30T20:11:52.000Z",
  "updated": "2008-04-02T22:15:19.000Z",
  "title": "GRB Energetics in the Swift Era",
  "authors": [
    "Daniel Kocevski",
    "Nathaniel Butler"
  ],
  "comment": "30 pages, 10 figures, Accepted to ApJ",
  "doi": "10.1086/586693",
  "categories": [
    "astro-ph"
  ],
  "abstract": "We examine the rest frame energetics of 76 gamma-ray bursts (GRBs) with known redshift that were detected by the Swift spacecraft and monitored by the satellite's X-ray Telescope (XRT). Using the bolometric fluence values estimated in Butler et al. 2007b and the last XRT observation for each event, we set a lower limit the their collimation corrected energy Eg and find that a 68% of our sample are at high enough redshift and/or low enough fluence to accommodate a jet break occurring beyond the last XRT observation and still be consistent with the pre-Swift Eg distribution for long GRBs. We find that relatively few of the X-ray light curves for the remaining events show evidence for late-time decay slopes that are consistent with that expected from post jet break emission. The breaks in the X-ray light curves that do exist tend to be shallower and occur earlier than the breaks previously observed in optical light curves, yielding a Eg distribution that is far lower than the pre-Swift distribution. If these early X-ray breaks are not due to jet effects, then a small but significant fraction of our sample have lower limits to their collimation corrected energy that place them well above the pre-Swift Eg distribution. Either scenario would necessitate a much wider post-Swift Eg distribution for long cosmological GRBs compared to the narrow standard energy deduced from pre-Swift observations. We note that almost all of the pre-Swift Eg estimates come from jet breaks detected in the optical whereas our sample is limited entirely to X-ray wavelengths, furthering the suggestion that the assumed achromaticity of jet breaks may not extend to high energies.",
  "revisions": [
    {
      "version": "v3",
      "updated": "2008-04-02T22:15:19.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "swift era",
      "grb energetics",
      "x-ray light curves",
      "collimation corrected energy",
      "distribution"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "journal": "The Astrophysical Journal",
      "year": 2008,
      "month": "Jun",
      "volume": 680,
      "number": 1,
      "pages": 531
    },
    "note": {
      "typesetting": "TeX",
      "pages": 30,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 757076,
      "adsabs": "2008ApJ...680..531K"
    }
  }
}