{
  "bibcode": "2009GCN..9451....1M",
  "body": "Mangano V., Sbarufatti B. (INAF-IASFPA), J. K. Cannizzo (NASA/UMBC)\nreport on behalf of the Swift XRT Team:\n\nWe have analyzed the first five orbits of Swift-XRT data of\nGRB 090530 (trigger 353567; Cannizzo, et al., GCN Circ. 9438),\nconsisting of 22 s in Windowed Timing (WT) mode from T+81 to T+103 s and\n9 ks in Photon Counting (PC) mode from T+105 s to T+24.4 ks.\n\nThe best position for the X-ray afterglow is the XRT UVOT-enhanced\nposition: RA, Dec = 179.41846, +26.59341 which is equivalent to:\n\nRA (J2000): 11h 57m 40.43s\nDec (J2000): +26d 35' 36.3\"\n\nwith an uncertainty of 1.5 arcsec (radius, 90% confidence), as given\nby Beardmore, et al., GCN Circ 9445.\n\nThe 0.3-10 keV X-ray light curve is best fitted by a broken powerlaw\nwith early decay index of about -5.7, late decay index -0.60+/-0.04\nand a break at about 140 s after the trigger. In the first orbit\na small amplitude flare is detected at T+300 s. Flaring activity\nis also visible along the later decay.\nIf decaying at the present rate, the predicted rate after 24h from the\ntrigger is 2.0e-2 counts/s. However, we remark that a second break\nfollowed by a steepening of the lightcurve is possibly expected.\nThe issue will be clarified with following Swift observations that\nwill resume on Sunday May 31st.\n\nThe average initial WT spectrum (covering the initial steep decay)\ncan be modeled as an absorbed power-law with index 2.3 (+0.5-0.4),\nabsorbing column NH < 11E20 cm-2 (three sigma upper limit) and\nobserved(unabsorbed) average flux in the 0.3-10 keV energy range of\n2.9(3.6)E-10 ergs cm-2 s-1.\nThe average PC spectrum (roughly covering the flatter part of the\nafterglow)\nis best fitted by an absorbed power-law with index 2.00+/-0.15\nThe absorbing column is NH = (8.2 -2.9+3.6)E20 cm-2 in excess with\nrespect to the Galactic value of 1.78E+20 cm-2 (Kalberla et al. 2005).\nThe average observed(unabsorbed) flux is 4.0(4.9)E-12 ergs cm-2 s-1.\nThe count-rate to flux conversion factor is 5.4E-11.\nAll quoted errors are at 90% confidence level.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00353567.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 9451,
  "createdOn": 1243717764000,
  "email": "vanessa@ifc.inaf.it",
  "subject": "GRB090530: Swift XRT refined analysis",
  "submitter": "Vanessa Mangano at INAF-IASFPA  <vanessa@ifc.inaf.it>",
  "eventId": "GRB 090530"
}