{
  "bibcode": "2009GCN..9198....1K",
  "body": "H. A. Krimm (CRESST/GSFC/USRA), A. P. Beardmore (U Leicester),\nP. A. Evans (U Leicester), O. Godet (U Leicester), C. Gronwall (PSU),\nC. Guidorzi (U Ferrara), P. T. O'Brien (U Leicester),\nK. L. Page (U Leicester), D. M. Palmer (LANL), M. Perri (ASDC),\nB. Sbarufatti (INAF-IASFPA), P. Schady (MSSL-UCL), G. Stratta (ASDC),\nG. Tagliaferri (INAF-OAB) and T. N. Ukwatta (GSFC/GWU) report on\nbehalf of the Swift Team:\n\nAt 07:55:19 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 090423 (trigger=350184).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 148.895, +18.160 which is \n   RA(J2000) = 09h 55m 35s\n   Dec(J2000) = +18d 09' 37\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a double-peaked\nstructure with a duration of about 20 sec.  The peak count rate\nwas ~2000 counts/sec (15-350 keV), at ~5 sec after the trigger. \n\nThe XRT began observing the field at 07:56:31.8 UT, 72.5 seconds after\nthe BAT trigger. Using promptly downlinked data we find a fading,\nuncatalogued X-ray source with an enhanced position: RA, Dec 148.8879,\n18.1497 which is equivalent to:\n   RA(J2000)  = 09h 55m 33.08s\n   Dec(J2000) = +18d 08' 58.9\"\nwith an uncertainty of 2.3 arcseconds (radius, 90% containment). This\nlocation is 44 arcseconds from the BAT onboard position, within the BAT\nerror circle. This position may be improved as more data are received;\nthe latest position is available at http://www.swift.ac.uk/sper. \n\nA power-law fit to a spectrum formed from promptly downlinked event\ndata gives a column density consistent with the Galactic value of\n2.89e+20 cm^-2 (Kalberla et al. 2005). \n\n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 77 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 expected extinction corresponding to E(B-V) of\n0.03. \n\n\n\n\nBurst Advocate for this burst is H. A. Krimm (krimm AT milkyway.gsfc.nasa.gov). \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.)",
  "circularId": 9198,
  "createdOn": 1240474478000,
  "email": "krimm@milkyway.gsfc.nasa.gov",
  "subject": "GRB 090423: Swift detection of a burst",
  "submitter": "Hans Krimm at NASA-GSFC  <krimm@milkyway.gsfc.nasa.gov>",
  "eventId": "GRB 090423"
}