{
  "bibcode": "2013GCN.15280....1M",
  "body": "D. Malesani (DARK/NBI), S. B. Cenko (NASA/GSFC), D. N. Burrows (PSU), A. \nY. Lien (NASA/GSFC/ORAU), P. A. Evans (U. Leicester), and N. Gehrels \n(NASA/GSFC) report:\n\nSwift has been continuously monitoring the X-ray counterpart of GRB \n130925A (Lien et al., GCN 15246), with data currently extending up to \n512 ks after the trigger. The intense X-ray flaring activity reported by \nBurrows et al. (GCN 15253) and Evans et al. (GCN 15254) ceased between \n12 and 28 ks after the trigger. The X-ray light curve from 27.9 to 512.4 \nks can be modelled with an initial power-law decay with an index of \nalpha = 0.84 +/- 0.03, followed by a possible break at 310 (+60, -50) ks \nto an alpha of 1.38 (+0.47, -0.23). The updated X-ray light curve is \navailable at the following URL:\n\nhttp://www.swift.ac.uk/xrt_curves/00571830/\n\nWhile the duration of the prompt emission and the flaring activity are \nextraordinary among GRBs (Suzuki et al., GCN 15248; Fitzpatrick, GCN \n15255; Markwardt et al., GCN 15257; Savchenko et al., GCN 15259; \nGolenetskii et al., GCN 15260; Jenke, GCN 15261; Hurley et al., GCN \n15278), the late-time behaviour is typical of long-duration GRB \nafterglows, and quite different from that of the TDE Swift J1644+57, \nwhich showed continuous flares and dips, with no regular power-law decay \n(e.g. Burrows et al. 2011, Nat, 476, 421). There is also no prior \ndetection of the source in BAT before the trigger (Markwardt et al., GCN \n15257).\n\nThe extremely long-lived high-energy emission coupled with the \nrelatively steady power-law X-ray decay at t > 20 ks is reminiscent of \nthe so-called \"ultra-long\" GRBs (Levan et al. 2013, arXiv:1302.2352), \nincluding GRB 101225A (Thoene et al. 2011, Nat, 480, 72; Campana et al. \n2011, Nat, 480, 69), GRB 111209A (Gendre et al. 2013, ApJ, 766, 30), and \nGRB 121027A. The origin of these events and their relation to \ntraditional long-duration GRBs (i.e., the core-collapse of a massive \nstar) remain controversial, so we encourage continued multi-wavelength \nfollow-up of this object.",
  "circularId": 15280,
  "createdOn": 1380649953000,
  "email": "malesani@dark-cosmology.dk",
  "subject": "GRB 130925A: continuing Swift/XRT monitoring",
  "submitter": "Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst  <malesani@dark-cosmology.dk>",
  "eventId": "GRB 130925A"
}