{
  "bibcode": "2009GCN..9734....1M",
  "body": "V. Mangano, B. Sbarufatti (INAF IASF Pa)\nreport on beahalf the Swift XRT Team:\n\n\nWe have analysed 9.8 ks of XRT data for GRB 090728 (Mangano et al. GCN\nCirc. 9725), from 116.9 s to 53.1 ks after the BAT trigger. The data\ncomprise 55.3 s in Windowed Timing (WT) mode from T+116.9 s to T+172.2\ns, with  the remainder in Photon Counting (PC) mode. The enhanced XRT\nposition for this burst was given by Osborne et al. (GCN. Circ 9729).\n\nThe 0.3-10 keV XRT light curve is well modeled by a doubly broken\npower law with initial decay slope -5.5 � 0.5, first break at\nT+204 � 10 s, plateau phase slope -0.11 � 0.14, second break\nat T+1.8 � 1.2 ks and final slope -1.7 � 0.1.\nDecaying at the present rate the source will reach a level of\n2e-4 counts/s on July 30 at 14:45 UT (48 h after the trigger).\n\nWe extracted the average WT spectrum of the early decay phase (55.3 s\nexposure), and the average PC spectra of the plateau phase (866 s\nexposure, from T+174 s to T+1071 s) and the final decay phase (7.4 ks\nexposure, from T+4383 s to T+18.4 ks). The three spectra are well fitted\nby an absorbed power law model with NH consistent with the Galactic\nvalue of 7.35e20 cm-2 (Kalberla et al. 2005) and photon indices of\n2.4 � 0.4, 1.8 � 0.2, and 2.0 � 0.3, respectively.\nThe average 0.3-10 keV observed [unabsorbed] fluxes are\n1.6e-10 [2.9e-10] erg cm-2 s-1, 2.7e-11 [3.0e-11] erg cm-2 s-1,\nand 1.5e-12 [2.3e-12] erg cm-2 s-1, respectively.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00358574.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 9734,
  "createdOn": 1248881200000,
  "email": "vanessa@ifc.inaf.it",
  "subject": "GRB 090728: Swift XRT refined analysis",
  "submitter": "Vanessa Mangano at INAF-IASFPA  <vanessa@ifc.inaf.it>",
  "eventId": "GRB 090728"
}