{
  "bibcode": "2018GCN.23261....1U",
  "body": "T. N. Ukwatta (LANL), A. P. Beardmore (U Leicester),\nA. A. Breeveld (UCL-MSSL), P. A. Evans (U Leicester),\nC. Gronwall (PSU), J.D. Gropp (PSU), J. A. Kennea (PSU),\nA. Y. Lien (GSFC/UMBC), K. L. Page (U Leicester), M. H. Siegel (PSU)\nand R. L. C. Starling (U Leicester) report on behalf of the Neil\nGehrels Swift Observatory Team:\n\nAt 15:22:22 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 180924A (trigger=863186).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 49.161, -58.505 which is \n   RA(J2000) = 03h 16m 39s\n   Dec(J2000) = -58d 30' 19\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a multi-peaked\nstructure with a duration of about 130 sec.  The peak count rate\nwas ~1492 counts/sec (15-350 keV), at ~1 sec after the trigger. \n\nThe XRT began observing the field at 15:23:39.1 UT, 76.8 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright,\nfading, uncatalogued X-ray source with an enhanced position: RA, Dec\n49.2002, -58.5321 which is equivalent to:\n   RA(J2000)  = 03h 16m 48.05s\n   Dec(J2000) = -58d 31' 55.6\"\nwith an uncertainty of 2.2 arcseconds (radius, 90% containment). This\nlocation is 122 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 consistent with the Galactic value of 2.03\nx 10^20 cm^-2 (Willingale et al. 2013). \n\nThe initial flux in the 2.5 s image was 1.35e-09 erg cm^-2 s^-1 (0.2-10\nkeV). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 82 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 100% of\nthe XRT 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\nXRT 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\nThis source lies within the current (Sector 2) field-of-view of TESS camera 3. \n\nBurst Advocate for this burst is T. N. Ukwatta (tilan.ukwatta AT gmail.com). \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": 23261,
  "createdOn": 1537803563000,
  "email": "caryl@swift.psu.edu",
  "subject": "GRB 180924A: Swift detection of a burst",
  "submitter": "Caryl Gronwall at PSU/Swift-UVOT  <caryl@swift.psu.edu>",
  "eventId": "GRB 180924A"
}