{
  "subject": "GRB 090621: Swift detection of a burst",
  "eventId": "GRB 090621",
  "bibcode": "2009GCN..9540....1C",
  "createdOn": 1245560039000,
  "circularId": 9540,
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>",
  "email": "palmer@lanl.gov",
  "body": "P.A. Curran (MSSL-UCL), W. H. Baumgartner (GSFC/UMBC),\nA. P. Beardmore (U Leicester), N. Gehrels (NASA/GSFC),\nS. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),\nC. B. Markwardt (CRESST/GSFC/UMD), K. L. Page (U Leicester),\nD. M. Palmer (LANL), M. Stamatikos (NASA/ORAU), M. C. Stroh (PSU),\nT. N. Ukwatta (GSFC/GWU) and H. Ziaeepour (UCL-MSSL) report on behalf\nof the Swift Team:\n\nAt 04:22:43 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 090621 (trigger=355303).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 10.986, +61.968 which is \n   RA(J2000) = 00h 43m 57s\n   Dec(J2000) = +61d 58' 04\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed weak emission during\nthe 8 seconds of the trigger interval.  The peak count rate\nwas ~1000 counts/sec (15-350 keV), at ~4 sec after the trigger. \n\nThere was a second BAT trigger (trigger=355304) at 04:27:05, about \n4 minutes after the initial trigger from the same location.  This \nportion of the BAT light curve is not immediately available from \nTDRSS, but the retrigger could indicate an extended prompt phase. \n\nThe XRT began observing the field at 04:24:40.46 UT, 117.3 seconds after\nthe BAT trigger. XRT found an uncatalogued, variable X-ray source located\nat RA, Dec 11.0191, 61.9417 which is equivalent to:\n   RA(J2000)  = 00h 44m 04.58s\n   Dec(J2000) = +61d 56' 30.2\"\nwith an uncertainty of 5.0 arcseconds (radius, 90% containment). This\nlocation is 110 arcseconds from the BAT onboard position, within the BAT\nerror circle.  There is a bright peak at about 250s after the initial trigger\nwhich could be X-ray emission during prolonged prompt emission. \n\n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 122 seconds after the BAT trigger. No credible afterglow candidate has\nbeen found in the initial data products. The 2.7'x2.7' sub-image covers 25% of\nthe BAT error circle. The typical 3-sigma upper limit has been about 19.6 mag. \nThe 8'x8' region for the list of sources generated on-board covers 100% of the\nBAT error circle. The list of sources is typically complete to about 18 mag. No\ncorrection has been made for the large, but uncertain extinction expected. \n\n\n\n\nBurst Advocate for this burst is P.A. Curran (pac AT mssl.ucl.ac.uk). \nPlease contact the BA by email if you require additional information\nregarding Swift followup of this burst. In extremely urgent cases, after\ntrying the Burst Advocate, you can contact the Swift PI by phone (see\nSwift TOO web site for information: http://www.swift.psu.edu/too.html.)"
}