TITLE:   GCN CIRCULAR
NUMBER:  7357
SUBJECT: GRB080303: Swift XRT refined analysis
DATE:    08/03/03 16:49:21 GMT
FROM:    Jirong Mao at INAF-OAB  <jirong.mao@brera.inaf.it>

GRB080303: Swift XRT refined analysis

J. Mao (INAF-OAB), A. Moretti (INAF-OAB), T. Sakamoto (NASA/UMBC),
C. Guidorzi (Univ. Bicocca & INAF-OAB) report on behalf of the Swift-XRT 
team:

We have analysed the Swift-XRT data obtained for
BAT GRB 080303 (trigger #304549, Sakamoto, et al., GCN Circ. 7351).
The data consist of 105 s in Windowed Timing (WT) mode, starting 80 s
after the BAT trigger and 206 s in Photon Counting (PC) mode.
The UVOT-enhanced XRT position was given in Evans et al. (GCN Circ. 7356).

The light-curve shows a simple power-law with a slope of alpha=1.65 ± 0.05.

The spectrum formed from all the WT data can be modeled with a power-law 
of photon index
Gamma = 1.88 ± 0.12, with an absorbing column of NH = (1.32 ± 0.03)e21 
cm^-2 (in excess
with respect to the Galactic value of 8.97e20 cm^-2). The spectrum 
formed from the PC data
can be modeled with a power-law of photon index Gamma = 1.81 ± 0.17, 
with an absorbing
column of NH = (5.72 ± 4.77)e20 cm^-2.

If the light-curve continues to decay with a slope of 1.65, the 
afterglow at 24 hour will be with
an expected count rate of 1.5e-4 count s^-1. This corresponds to an 
observed (unabsorbed) flux
of 7E-15(9e-15) erg cm-2 s-1.

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