{
  "bibcode": "2012GCN.13525....1C",
  "body": "J. R. Cummings (NASA/UMBC), S. D. Barthelmy (GSFC),\nM. M. Chester (PSU), H. A. Krimm (CRESST/GSFC/USRA),\nN. P. M. Kuin (UCL-MSSL), C. B. Markwardt (NASA/GSFC),\nA. Maselli (INAF-IASFPA), D. M. Palmer (LANL), M. H. Siegel (PSU) and\nT. N. Ukwatta (MSU) report on behalf of the Swift Team:\n\nAt 22:25:11 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 120728A (trigger=529021).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 137.100, -54.437, which is \n   RA(J2000)  =  09h 08m 24s\n   Dec(J2000) = -54d 26' 13\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve shows a peak with structure\nwith a total duration of about 20 sec.  The peak count rate\nwas ~1500 counts/sec (15-350 keV), at ~3 sec after the trigger. \n\nThe XRT began observing the field at 22:27:38.8 UT, 147.8 seconds after\nthe BAT trigger. Using promptly downlinked data we find a fading,\nuncatalogued X-ray source located at RA, Dec 137.09412, -54.43783 which\nis equivalent to:\n   RA(J2000)  = 09h 08m 22.59s\n   Dec(J2000) = -54d 26' 16.2\"\nwith an uncertainty of 4.1 arcseconds (radius, 90% containment). This\nlocation is 12 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 5.18\nx 10^21 cm^-2 (Kalberla et al. 2005). \n\nUVOT took a finding chart exposure of 250 seconds with the U filter starting\n148 seconds after the BAT trigger. No credible afterglow candidate has been\nfound in the initial data products. The 2.7'x2.7' sub-image covers 100% of the\nXRT error circle. Because of the density of catalogued stars, further analysis\nis required to report an upper limit for any afterglow in the sub-image. The\n8'x8' region for the list of sources generated on-board covers 100% of the XRT\nerror circle. Because of the density of catalogued stars, further analysis is\nrequired to report an upper limit for any afterglow in the region. No\ncorrection has been made for the large, but uncertain extinction expected. \n\nBurst Advocate for this burst is J. R. Cummings (jayc 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": 13525,
  "createdOn": 1343515075000,
  "email": "scott@milkyway.gsfc.nasa.gov",
  "subject": "GRB 120728A: Swift detection of a burst",
  "submitter": "Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>",
  "eventId": "GRB 120728A"
}