{
  "bibcode": "2011GCN.12308....1Z",
  "body": "B.-B. Zhang (PSU) and D. Grupe (PSU) reports on behalf of the Swift-XRT\nteam:\n\n\nSwift began a target of opportunity observation of the IPN-detected\nburst: GRB110825A (Hurley et al. et al. GCN Circ. 12307) on August 26,\n2011 at 01:05 UT, approximately 22.7 hours after the burst was detected\nby IPN. Swift data for these observations utilize Target ID 20183.\n\nWe have analysed 2.9 ks of XRT data for this burst, from 81.3 ks to\n94.0 ks after the IPN trigger. The data are entirely in Photon Counting\n(PC) mode. An X-ray source is detected within the XRT field-of-view.\nThe refined XRT position is RA, Dec = 44.79846, +15.42733 which is\nequivalent to:\n\nRA (J2000): 02 59 11.63\nDec(J2000): +15 25 38.4\n\nwith an uncertainty of 3.9 arcsec (radius, 90% confidence). This\nposition is 346 arcsec from the IPN position and about 180 arcsec from\nthe edge of IPN error box (see\nhttp://www.personal.psu.edu/buz12/IPN_ERRORBOX_VS_XRT_GRB110825A.png). \nWe cannot determine at the present time whether the source is fading.\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 1.8 (+0.8, -0.4). The\nbest-fitting absorption column is consistent with the Galactic value of\n9.9 x 10^20 cm^-2 (Kalberla et al. 2005). The count rate for the X-ray\nsource is about 0.01 count/sec, which is relatively bright when\ncomparing to other GRB's X-ray afterglow at t-T0=10^5 seconds. The\ncounts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum  is 3.9 x 10^-11 (4.7 x 10^-11) erg cm^-2\ncount^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     0 (+1.7, -0) x 10^21 cm^-2\nGalactic foreground: 9.9 x 10^20 cm^-2\nExcess significance: <1.6 sigma\nPhoton index:\t     1.8 (+0.8, -0.4)\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00020183.\n\n\nNo source was found from UVOT data within the XRT error circle.\nPreliminary 3-sigma up-limits are : \n\nFilter\t     EXPOSURE\t    Mag\n---------------------------------------------------\n    v\t &    579 &   >19.19  \n    u\t &    1365 &  >20.79 \nwhite\t &    895.63 &\t >21.40\n---------------------------------------------------\n\n\nWe notice that there is no known source at the X-ray source position in\nSimbad or the NED. We also notice that the RASS data for this position\nwere not deep enough to detect a source of this flux (0.01 count/sec).\n\nWe have scheduled further Swift TOO for this target. \n\nThis circular is an official product of the Swift-XRT team.\n\n\nBurst Advocate for this burst is B.-B. Zhang (bbzhang AT psu.edu).\nPlease contact the BA by email if you require additional information\nregarding Swift followup of this burst. In extremely urgent cases,\nafter\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": 12308,
  "createdOn": 1314394160000,
  "email": "bbzhang@psu.edu",
  "subject": "GRB110825A: Swift target of opportunity observation",
  "submitter": "Binbin Zhang at PSU  <bbzhang@psu.edu>",
  "eventId": "GRB 110825A"
}