{
  "bibcode": "2010GCN.11159....1I",
  "body": "S. Immler (CRESST/GSFC/UMD), S. D. Barthelmy (GSFC),\nW. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester),\nS. Campana (INAF-OAB), V. D'Elia (ASDC), P. A. Evans (U Leicester),\nJ. M. Gelbord (PSU), O. Godet (U Leicester), C. Gronwall (PSU),\nC. Guidorzi (U Ferrara), S. T. Holland (CRESST/USRA/GSFC),\nE. A. Hoversten (PSU), O. M. Littlejohns (U Leicester),\nF. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester),\nJ. P. Osborne (U Leicester), C. Pagani (U Leicester),\nK. L. Page (U Leicester), D. M. Palmer (LANL), T. A. Pritchard (PSU),\nA. Rowlinson (U Leicester), 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 13:34:10 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 100901A (trigger=433065).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 27.245, +22.744, which is \n   RA(J2000)  =  01h 48m 59s\n   Dec(J2000) = +22d 44' 39\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a single symmetric\npeak structure with a duration of about 10 sec.  The peak count rate\nwas ~800 counts/sec (15-350 keV), at ~1 sec after T_zero. \n\nThe XRT began observing the field at 13:36:51.0 UT, 160.6 seconds after\nthe BAT trigger. Using promptly downlinked data we find an uncatalogued\nX-ray source with an enhanced position: RA, Dec 27.2642, 22.7584 which\nis equivalent to:\n   RA(J2000)  = 01h 49m 3.41s\n   Dec(J2000) = +22d 45' 30.1\"\nwith an uncertainty of 3.0 arcseconds (radius, 90% containment). This\nlocation is 82 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\n7.08e+20 cm^-2 (Kalberla et al. 2005). \n\nUVOT took a finding chart exposure of 150 seconds with the White\nfilter  starting 147 seconds after the BAT trigger. There is a\ncandidate afterglow in  the rapidly available 2.7'x2.7' sub-image at \n  RA(J2000)  =\t01:49:03.42 =  27.26424 \n  DEC(J2000) = +22:45:30.8  =  22.75856  with a 90%-confidence error\nradius of about 0.81 arc sec. This position is 0.6  arc sec. from the\ncenter of the XRT-Enhanced error circle. The estimated magnitude is\n19.67 with a 1-sigma error of about  0.18. No correction has been made\nfor the expected extinction corresponding to E(B-V) of 0.10. \n\nBurst Advocate for this burst is S. Immler (immler 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": 11159,
  "createdOn": 1283349655000,
  "email": "scott@milkyway.gsfc.nasa.gov",
  "subject": "GRB 100901A: Swift detection of a burst with an optical afterglow",
  "submitter": "Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>",
  "eventId": "GRB 100901A"
}