{
  "bibcode": "2007GCN..6421....1G",
  "body": "C. Guidorzi, P. Romano (Univ Bicocca&INAF-OAB), A. Moretti (INAF-OAB),\nS.D. Vergani (DIAS-DCU) report on behalf of the Swift team:\n\nWe have analysed the first two orbits of GRB 070518 (Guidorzi\net al., GCN Circ. 6415) with total observing times of 186 s in\nWindowed Timing mode and 4.2 ks in Photon Counting mode in the Swift XRT.\nThe Photon Counting mode image provides a refined XRT\nposition at RA,DEC(J200) = 254.19800, +55.29444 which is\n\nRA(J2000)  = 16h 56m 47.52s\nDec(J2000) = +55d 17' 40.0\"\n\nwith an uncertainty of 3.9 arcsec (radius, 90% containment).\nThis is  2.5 arcsec from the initial X-ray position,\n2.8 arcsec from the UVOT position (GCN Circ. 6415)\nand 57 arcsec from the BAT refined position (Krimm et al., GCN Circ. 6417).\n\nThe XRT light curve exhibits an initial flaring behaviour up to\n~T+200 s, after which a steep decay (4.7 � 0.4) follows after the\nlast flare, with a break at T+460 (+/- 40) s to a shallower\ndecay (1.11 � 0.13) up to T+11ks.\n\nWe extracted two spectra from the WT data during the flaring\nactivity, due to a strong spectral evolution.\nThe first spectrum, from 77 s to 158 s, can be fit with an\nabsorbed power law with a photon index of 2.3+/-0.1 and\ncolumn density of (9.6+/-1.6)E20 cm^-2 significantly in excess\nof the Galactic value (2.2E20 cm^-2; Dickey & Lockman, 1990).\nThe second spectrum, from 165 to 253 s, has a photon index\nof 2.9+/-0.1 and same column density as that of the first spectrum.\n\nThe absorbed (unabsorbed) 0.3-10.0keV flux for the first spectrum\nis 5.1E-10 (7.2E-10) ergs cm^-2 s^-1.\n\nAssuming the source continues to decay at the same rate, we predict\nan XRT count rate of 6.3E-4 counts/s at T+24 hours, which corresponds\nto an observed (unabsorbed) flux of 2.0E-14 (2.8E-14) ergs cm^-2 s^-1.\n\nThis circular is an official product of the Swift XRT team.",
  "circularId": 6421,
  "createdOn": 1179561058000,
  "email": "cristiano.guidorzi@brera.inaf.it",
  "subject": "GRB 070518: Swift-XRT refined analysis",
  "submitter": "Cristiano Guidorzi at INAF-OAB  <cristiano.guidorzi@brera.inaf.it>",
  "eventId": "GRB 070518"
}