{
  "bibcode": "2011GCN.11891....1K",
  "body": "H. A. Krimm (CRESST/GSFC/USRA) and S. D. Barthelmy (GSFC) report\non behalf of the Swift/BAT team:\n\nWe report on the time history of the discovery outburst of Swift\nJ164449.3+573451 and archival searches for past emission.\n\nThe current outburst started on 2011-Mar-25 (MJD 55645) with a detection\nof 0.0059 � 0.0016 ct/s/cm2 (~25 mCrab).  BAT first triggered on the\nsource on 2011-Mar-28 (Cummings et al, GCN 11823).  There were numerous\nflares as high as 220 mCrab over the next three days, then the count\nrate dropped to an average level of 0.0009 ct/s/cm2 and the flares\nstopped. For the past three days the rate shown a slight increase to\n0.0015 � 0.0005 ct/s/cm2 (~7 mCrab) on 2001-Apr-05, although no flares\nabove 40 mCrab have been seen.  For a detailed time history of the early\npart of the outburst see Sakamoto et al, GCN 11842.\n\nThe Swift/BAT transient monitor archival data were searched back to\nFebruary 12, 2005 for previous detections of Swift J164449.3+573451.\nThese searches were made on three different time scales with the\nfollowing results:\n\nOn a 16-day timescale (the longest available), we set a 3-sigma upper\nlimit of 0.0011 ct/s/cm2 (~5 mCrab).\n\nOn a 1-day timescale, there were three isolated days before the outburst\nwhen the source was found at above the 3-sigma level:\n2009-Mar-31 (MJD 54921) 0.0036 � 0.0011 ct/s/cm2\n2009-Sep-14 (MJD 55088) 0.0036 � 0.0010 ct/s/cm2\n2011-Mar-14 (MJD 55634) 0.0035 � 0.0011 ct/s/cm2\nAll three episodes correspond to approximately 15 mCrab.   However, given\n1866 independent days examined, three 3-sigma points is consistent with\nstatistics.\n\nFor all other 1-day images, we can set a 3-sigma upper limit.  This\nlimit varies depending on the exposure of the source, with 90% of the\ndaily limits within the range of 0.0015 ct/s/cm2 to 0.010 ct/s/cm2.\n\nOn shorter time scales, we are unable to set a limit below the 6-sigma\nlevel for a previously unknown source.  Before March 2011 there was no\ninterval when Swift J164449.3+573451 was seen above 6-sigma on any\ntime scale from 64 seconds to a full Swift pointing (nominally 1200\nseconds).  Corresponding count rate limits cannot be specified since\nthey depend critically on the time scale and location of the source in\nthe BAT field of view.",
  "circularId": 11891,
  "createdOn": 1302126050000,
  "email": "hans.krimm@nasa.gov",
  "subject": "GRB 110328A/Swift J164449.3+573451: BAT recent rate increase and pre-outburst,light curve",
  "submitter": "Hans Krimm at NASA-GSFC  <hans.krimm@nasa.gov>",
  "eventId": "GRB 110328A"
}