GCN Circular 7014

J. Racusin (PSU) reports on behalf of the Swift-XRT Team:

We have analysed the first 2 orbits of Swift-XRT data obtained for GRB
071028 (Racusin et al. GCN Circ. 7012
Not found
 
 
), totaling 61 s of Windowed Timing
(WT) data and 2.9 ks of Photon Counting (PC) data.

Using 399 s of overlapping XRT Photon Counting mode and UVOT V-band data,
we find an astrometrically corrected X-ray position (using the XRT-UVOT
alignment and matching UVOT field sources to the USNO-B1 catalogue): RA,
Dec = 119.81936, 21.48482 which is equivalent to:

RA (J2000):  07 59 16.65
Dec (J2000): +21 29 05.4

with an uncertainty of 1.9 arcsec (radius, 90% confidence).  This is 6.5
arcsec from the previous XRT position (GCN Circ. 7012
Not found
 
 
), and 51 arcsec from
the refined BAT position (Cummings et al., GCN Circ. 7013
Not found
 
 
).

The bright X-ray light-curve can be fit by a broken power-law, with an
initial steep decay index of 3.3 +/- 0.4 followed by a flatter decay index
of 1.1 +/- 0.3 after a break at 475 +/- 150 seconds.

The WT data (124-182 seconds) can be modeled as an absorbed power-law,
with photon index of 1.9 +/- 0.2 and a total absorbing column of NH = (5.9
+/- 5.6)e20 cm^-2, consistent with the Galactic value of 5.1e20 cm^-2. The
0.3-10 keV observed (unabsorbed) flux during this time is 3.1e-10
(3.6e-10) erg cm^-2 s^-1.

Assuming the source continues to decay with the same decay index of 1.1,
we predict an XRT count rate of 5.5e-4 counts/s at T+24 hours, which
corresponds to an 0.3-10.0 keV observed flux of 2.3e-14 ergs cm^-2 s^-1.

This circular is an official product of the Swift-XRT team.