{
  "bibcode": "2015GCN.18050....1R",
  "body": "J. L. Racusin (NASA/GSFC), A. P. Beardmore (U Leicester),\nJ. R. Cummings (NASA/UMBC), K. L. Page (U Leicester),\nD. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the\nSwift Team:\n\nAt 05:46:35 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 150724A (trigger=650141).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 97.540, -19.154 which is \n   RA(J2000) = 06h 30m 09s\n   Dec(J2000) = -19d 09' 12\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed multiple peaks\nstructure with a duration of about 40 sec.  The peak count rate\nwas ~1412 counts/sec (15-350 keV), at ~1 sec after the trigger. \n\nThe XRT began observing the field at 05:48:18.6 UT, 102.6 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright,\nfading, uncatalogued X-ray source located at RA, Dec 97.56060,\n-19.16395 which is equivalent to:\n   RA(J2000)  = 06h 30m 14.54s\n   Dec(J2000) = -19d 09' 50.2\"\nwith an uncertainty of 3.7 arcseconds (radius, 90% containment). This\nlocation is 78 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 2.94\nx 10^21 cm^-2 (Willingale et al. 2013). \n\nThe initial flux in the 2.5 s image was 1.27e-09 erg cm^-2 s^-1 (0.2-10\nkeV). \n\nUVOT took a finding chart exposure of 250 seconds with the U filter starting\n108 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. The typical 3-sigma upper limit has been about 19.2 mag. The\n8'x8' region for the list of sources generated on-board covers 100% of the XRT\nerror circle. The list of sources is typically complete to about 18.0 mag. No\ncorrection has been made for the expected extinction corresponding to E(B-V) of\n0.27. \n\nBurst Advocate for this burst is J. L. Racusin (judith.racusin AT 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": 18050,
  "createdOn": 1437717732000,
  "email": "palmer@lanl.gov",
  "subject": "GRB 150724A: Swift detection of a burst",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>",
  "eventId": "GRB 150724A"
}