TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4952
SUBJECT: GRB060403: XRT refined analysis
DATE:    06/04/04 12:43:28 GMT
FROM:    Vanessa Mangano at INAF-IASFPA  <vanessa@ifc.inaf.it>

T. Mineo, V. Mangano, V. La Parola, G. Cusumano (INAF-IASFPA),
J. Kennea (PSU), P.T. Boyd (NASA/GSFC), D.N. Burrows (PSU)
report on behalf of the Swift XRT team:

We analyzed the Swift XRT data of GRB 060403 (Boyd et al. GCN 4945).
The observation started 52 s after the BAT trigger in Windowed Timing (WT)
mode because before slewing to the GRB position, XRT was observing
SGR1900+14 in manual state. The instrument then switched to auto state,
taking the initial image frame for on board centroiding 222 s after the
trigger, as reported in GCN 4945.
The data we report on consisted of 5.5 ks exposure in WT mode
and 15 ks exposure in Photon Counting (PC) mode.

The 0.2-10 keV light curve shows a clear power law decay with
slope -1.49+/-0.04.

The average WT spectrum accumulated during the first orbit (from 52 s
to 300 s after the trigger) is well fitted by a power law with photon
index 1.61+/-0.22, absorbed at lower energies by a column of
(8.1+/-2.1) x 10^21 cm^-2, higher than the galactic value (4.9 x 10^21
cm^-2).
The 0.2-10 keV unabsorbed flux is 1.61 x 10^-11 ergs cm^-2 s^-1.
If the burst continues decaying at the current rate we
estimate an XRT count rate of 1 x 10^-4 counts/s at T+48hr,
which corresponds to an unabsorbed 0.2-10 keV flux
of 1x 10^-14 ergs cm^-2 s^-1.

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