{
  "bibcode": "2015GCN.17765....1P",
  "body": "K. L. Page (U Leicester), M. M. Chester (PSU), N. Gehrels (NASA/GSFC),\nJ. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL),\nF. E. Marshall (NASA/GSFC), T. Sakamoto (AGU),\nB. Sbarufatti (INAF-OAB/PSU) and M. H. Siegel (PSU) report on behalf\nof the Swift Team:\n\nAt 01:30:40 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 150428A (trigger=639275).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 188.543, +6.981 which is \n   RA(J2000) = 12h 34m 10s\n   Dec(J2000) = +06d 58' 51\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a complex structure \nwith a duration of about 50 sec.  The peak count rate\nwas ~1700 counts/sec (15-350 keV), at ~17 sec after the trigger. \n\nThe XRT began observing the field at 01:33:36.7 UT, 175.9 seconds after\nthe BAT trigger. Using promptly downlinked data we find an uncatalogued\nX-ray source located at RA, Dec 188.53889, 6.95211 which is equivalent\nto:\n   RA(J2000)  = 12h 34m 09.33s\n   Dec(J2000) = +06d 57' 07.6\"\nwith an uncertainty of 3.7 arcseconds (radius, 90% containment). This\nlocation is 105 arcseconds from the BAT onboard position, within the\nBAT error circle. This position may be improved as more data are\nreceived; the latest position is available at\nhttp://www.swift.ac.uk/sper. \n\nA power-law fit to a spectrum formed from promptly downlinked event\ndata gives a column density in excess of the Galactic value (1.63 x\n10^20 cm^-2, Willingale et al. 2013), with an excess column of 9.3\n(+6.64/-5.03) x 10^21 cm^-2 (90% confidence). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 179 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 none of\nthe XRT error circle. The 8'x8' region for the list of sources generated\non-board covers 100% of the XRT error circle. The list of sources is typically\ncomplete to about 18 mag. No correction has been made for the expected\nextinction corresponding to E(B-V) of 0.02. \n\nBurst Advocate for this burst is K. L. Page (klp5 AT leicester.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.)",
  "circularId": 17765,
  "createdOn": 1430186032000,
  "email": "klp5@leicester.ac.uk",
  "subject": "GRB 150428A: Swift detection of a burst",
  "submitter": "Kim Page at U.of Leicester  <klp5@leicester.ac.uk>",
  "eventId": "GRB 150428A"
}