[vsnet-grb-info 2644] GRB060111 : XRT refined analysis

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4481
SUBJECT: GRB060111 : XRT refined analysis
DATE:    06/01/11 13:23:02 GMT
FROM:    Michael Goad at U Leicester  <mrg at star.le.ac.uk>

M.R. Goad, A.P. Beardmore, K. Page (U. Leicester), D. Burrows (PSU), R. Fink
(GSFC), M. Ajello (MPE) report on behalf of the Swift XRT team.

>From analysis of 2.5 ks of Photon Counting mode data of GRB060111 (Zane et
al., GCN 4479) starting in the 2nd orbit of observations, we obtain a refined
XRT position of RA: 18h 24m 49.0s, Dec:+37d 36m 16.1s (J2000) with an
uncertainty of 3.6 arcsec (90% containment). This includes the latest XRT
boresight correction. This refined position is 25.1 arcsec from the BAT
on-board position and 5 arcsec from the XRT on-board position quoted in GCN
4479.

We have also analysed 400 s of XRT Windowed Timing mode observations starting
78 s after the BAT trigger. The XRT lightcurve displays 3 large flares with a
peak count rate of approximately 150 ct/s occurring 280 s after the BAT
trigger. The light-curve has an underlying powerlaw decay of slope -1.3.

The XRT WT mode 0.3-10 keV spectrum is well represented by an absorbed
powerlaw with photon index 2.35 +/-0.04 with a mean unabsorbed flux of 2.5e-9
ergs/cm2/s. We find evidence for excess NH of 2.4e21 cm^-2.

The predicted 0.3-10 keV unabsorbed flux 24 hours after the BAT trigger is
1.2e-13 ergs/cm2/s