{
  "bibcode": "2007GCN..6779....1S",
  "body": "Giulia Stratta (ASDC), Matteo Perri (ASDC) and David\nBurrows (PSU) report, on behalf of the Swift XRT team:\n\nWe have analyzed the first 9 orbits of Swift-XRT\ndata on GRB 070911 (GCN 6777, Krimm et al.) for a\ntotal of 6.8 ks of exposure taken in Photon Counting\nmode starting 14.5 hours after the burst.\nThis is the first BAT GRB after Swift safe-hold recovery.\nSwift-XRT detected an uncatalogued, fading source\nat the following coordinates\nRA,Dec 25.8094,-33.4842 which is\n\n  RA(J2000)  = 01h 43m 14.26s\n  Dec(J2000) = -33d 29' 03.1\"\n\nwith an estimated error radius of 6 arcseconds\n(90% confidence). This error radius has been increased\nto take into account the uncertainties in the pointing\ncalibration during Swift's reactivation phase.\nThis position is 0.5' from the BAT refined position\n(GCN 6778, Palmer et al.). We note however that XRT position\nuncertanties are currently being re-validated.\n\nThe 0.3-10 keV X-ray light curve from T0+14.5 h to T0+27.3 h\ncan be fit with a simple power law model.\nThe best fit decay index is alpha=-1.5+/-0.2\n\nThe 0.3-10.0 keV X-ray spectrum with 6.8 ks of integration\ntime, is well fit by an absorbed power law with a\nphoton index of 2.2 +/- 0.3 and a total column density of\nNH=(1.3+/-0.5)e21 cm**-2 (chi2/dof=0.8/6).\nThe Galactic column density in the direction of the source\nis 2.4e20 cm**-2 (Dickey & Lockmann 1990).\nThe 0.3-10 keV observed flux is 1.9e-12 erg cm**-2 s**-1\n(unabsorbed: 2.8e-12 erg cm**-2 s**-1).\nWe note that the XRT CCD is now operating with a raised\nsubstrate voltage, and thus has a different gain.\nThe new gain is not yet well calibrated, and so our spectral\nresults are only preliminary.\n\nAssuming the X-ray emission continues to decline at the same\nrate, we predict a 0.3-10 keV count rates of 0.02 cts/s 2 days\nafter the burst trigger, that corresponds to a flux of\n1.3e-12 erg cm**-2 s**-1.\n\nThis is an official product of the Swift XRT team.",
  "circularId": 6779,
  "createdOn": 1189617712000,
  "email": "capalbi@asdc.asi.it",
  "subject": "GRB 070911: Swift XRT refined analysis",
  "submitter": "Milvia Capalbi at ISAC/ASDC  <capalbi@asdc.asi.it>",
  "eventId": "GRB 070911"
}