{
  "bibcode": "2010GCN.10998....1M",
  "body": "D. C. Morris (GWU/GSFC), M. M. Chester (PSU), J. M. Gelbord (PSU),\nC. Guidorzi (U Ferrara), S. T. Holland (CRESST/USRA/GSFC),\nH. A. Krimm (CRESST/GSFC/USRA), V. Mangano (INAF-IASFPA),\nP. T. O'Brien (U Leicester), K. L. Page (U Leicester),\nD. M. Palmer (LANL), B. Sbarufatti (INAF-OAB/IASFPA),\nM. H. Siegel (PSU), M. Stamatikos (OSU/NASA/GSFC) and\nR. L. C. Starling (U Leicester) report on behalf of the Swift Team:\n\nAt 05:42:17 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 100727A (trigger=430094).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 154.166, -21.364 which is \n   RA(J2000) = 10h 16m 40s\n   Dec(J2000) = -21d 21' 51\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a single-peaked\nstructure with a duration of about 50 sec, with possible additional\nactivity around T+175.  The peak count rate\nwas ~3300 counts/sec (15-350 keV), at ~2 sec after the trigger. \n\nThe XRT began observing the field at 05:43:14.4 UT, 56.6 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright,\nuncatalogued X-ray source located at RA, Dec 154.17823, -21.39002 which\nis equivalent to:\n   RA(J2000)  = 10h 16m 42.78s\n   Dec(J2000) = -21d 23' 24.1\"\nwith an uncertainty of 3.9 arcseconds (radius, 90% containment). This\nlocation is 100 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\n5.09e+20 cm^-2 (Kalberla et al. 2005). \n\nThe initial flux in the 2.5 s image was 1.29e-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 65 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. \nData from the list of sources generated on-board are not available at this\ntime. No correction has been made for the expected extinction corresponding to\nE(B-V) of 0.05. \n\nBurst Advocate for this burst is D. C. Morris (david.c.morris 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": 10998,
  "createdOn": 1280210160000,
  "email": "palmer@lanl.gov",
  "subject": "GRB 100727A: Swift detection of a burst",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>",
  "eventId": "GRB 100727A"
}