TITLE:   GCN CIRCULAR
NUMBER:  10467
SUBJECT: GRB 100302A: Swift-XRT refined analysis
DATE:    10/03/03 17:09:17 GMT
FROM:    Valerio D'Elia at INAF-OAR  <delia@oa-roma.inaf.it>

V. D'Elia, M. Perri (ASDC) and J.R. Cummings (NASA/UMBC) report
on behalf of the Swift-XRT team:

We have analysed the first 3 orbits of Swift-XRT data obtained from
GRB 100302A (trigger 414592; Cummings, et al., GCN Circ. 10458)
from 125 s to 28.8 ks after the BAT trigger.

The best position of the X-ray afterglow is the UVOT enhanced XRT
position given in Goad et al. (GCN Circ. 10460).

The 0.3-10 keV light curve shows a multiple peak structure, with
three main spikes at about T+200, T+250 and T+400s, followed by a
fast decay with index 3.35+-0.3 and by a break at 1ks. Later time
data are fitted by a second power law with a decay index of
0.26+-0.12.

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.28 (-0.15, +0.17). The
best-fitting absorption column is 1.1 (-0.20, +0.17) x 10^21 cm^-2, in
excess of the Galactic value of 1.9 x 10^20 cm^-2 (Kalberla et al.
2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum is 3.3 x 10^-11 (4.7 x 10^-11) erg
cm^-2 count^-1.

If the light curve continues to decay with a power-law decay index of
0.26, the count rate at T+24 hours will be 0.01 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.3 x
10^-13 (4.7 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00414592.

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