GCN Circular 7490
Dirk Grupe and Peter Brown (PSU) report on behalf of the Swift-XRT team: The Swift-XRT started observing GRB 080319D (trigger=306793, Brown et al. GCN 7453) at 17:07:37 UT, 148 seconds after the BAT trigger. The astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue) is: RA, Dec = 99.47254, +23.94275 which is equivalent to: RA (J2000): 06 37 53.41 Dec (J2000): +23 56 33.9 with an uncertainty of 1.7 arcsec (radius, 90% confidence). The 0.3-10 keV X-ray light curve starts with three flares up to 20 counts/s. The afterglow decays very fast and started to flatten at about 1000 s after the burst. The light curves shows another break at about 5 ks after the burst and is currently decaying with a decay slope of 1.3. The spectrum of the PC data can be well fit by an absorbed single powerlaw with photon index 2.12 � 0.27 and column density of (3.8 � 1.4)e21 cm-2. This is in excess of the Galactic column density of 2.17e21 cm-2 in this direction. Using this spectrum we estimated a count rate to flux conversion of 1 count/s converts to 6.28e-11 ergs/cm2/s. If the underlying powerlaw decay continues as is, we predict an XRT count rate of 1.6e-3 counts/s at T+24 hours and 6.5e-4 counts/s at T+48 hours after the burst, or 1.0e-13 ergs/s/cm2 and 4.1e-14 ergs/s/cm2, respectively. This circular is an official product of the Swift-XRT team.