TITLE:   GCN CIRCULAR
NUMBER:  4287
SUBJECT: GRB051117A : XRT refined analysis
DATE:    05/11/17 19:32:08 GMT
FROM:    Michael Goad at U Leicester  <mrg@star.le.ac.uk>

M. Goad, K. Page, D. Burrows (PSU), K. Hurley, (Berkeley), M. Chester (PSU)
report on behalf of the Swift XRT team.

From analysis of 2.3 ks of Photon Counting mode data of GRB051117A (Band et
al., GCN 4280) we obtain a refined XRT position of RA: 15h 13m 33.8s, Dec:+30d
52m 13.3s (J2000) with an uncertainty of 3.4 arcsec (90% containment). This
includes the latest XRT boresight correction. This refined position is 41
arcsec from the BAT on-board position and 3.4 arcsec from the UVOT position
quoted in GCN 4280.

We have also analysed 1.77 ks of XRT Windowed Timing mode observations
starting 113 s after the BAT trigger. The XRT lightcurve displays multiple
flares with a peak count rate of approximately 180 ct/s occurring 134 s after
the BAT trigger. The early underlying decay slope of the XRT lightcurve is a
powerlaw with slope ~1.1+/-0.1.

The XRT WT mode 0.2-10 keV spectrum is well represented by an absorbed
powerlaw with photon index 2.23+/-0.02 with a mean unabsorbed flux of 2.6E-09
ergs/cm2/s (between 113 s and 5.2 ks after the burst). We find evidence for
excess NH above the Galactic value of 2.0e21 cm^-2.