{
  "bibcode": "2011GCN.12450....1M",
  "body": "F. E. Marshall (NASA/GSFC), S. D. Barthelmy (GSFC),\nA. P. Beardmore (U Leicester), D. N. Burrows (PSU),\nM. M. Chester (PSU), V. D'Elia (ASDC), N. Gehrels (NASA/GSFC),\nS. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),\nN. P. M. Kuin (UCL-MSSL), V. Mangano (INAF-IASFPA),\nD. M. Palmer (LANL), M. H. Siegel (PSU),\nR. L. C. Starling (U Leicester), C. A. Swenson (PSU),\nG. Tagliaferri (INAF-OAB), E. Troja (NASA/GSFC/ORAU) and\nB.-B. Zhang (PSU) report on behalf of the Swift Team:\n\nAt 17:26:24 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 111018A (trigger=505801).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 271.500, -3.871 which is \n   RA(J2000)  =  18h 06m 00s\n   Dec(J2000) = -03d 52' 16\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve shows two weak peaks\nat T+0 and T+30 sec with a total duration of about 40 sec.  The peak count rate\nwas ~500 counts/sec (15-350 keV), at ~0 sec after the trigger. \n\nThe XRT began observing the field at 17:28:27.6 UT, 123.0 seconds after\nthe BAT trigger. The position determined from promptly downlinked data\ndiffers significantly from the on-board position, suggesting that the\nXRT may have centroided on a cosmic ray; the initial XRT position\nnotice should be treated with caution. Using promptly downlinked data\nwe find an uncatalogued X-ray source located at RA, Dec 271.48887,\n-3.90719 which is equivalent to:\n   RA(J2000)  = 18h 05m 57.33s\n   Dec(J2000) = -03d 54' 25.9\"\nwith an uncertainty of 3.8 arcseconds (radius, 90% containment). This\nlocation is 135 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.  We cannot determine whether the source is\nfading at the present time. \n\nA power-law fit to a spectrum formed from promptly downlinked event\ndata gives a column density consistent with the Galactic value of 2.54\nx 10^21 cm^-2 (Kalberla et al. 2005). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 132 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\n2.16. \n\nBurst Advocate for this burst is F. E. Marshall (marshall 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": 12450,
  "createdOn": 1318959831000,
  "email": "scott@milkyway.gsfc.nasa.gov",
  "subject": "GRB 111018A: Swift detection of a burst",
  "submitter": "Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>",
  "eventId": "GRB 111018A"
}