[vsnet-grb-info 7324] GRB 090205: Swift-XRT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8891
SUBJECT: GRB 090205: Swift-XRT refined analysis
DATE:    09/02/06 15:58:50 GMT
FROM:    Matteo Perri at ISAC/ASDC  <perri at asdc.asi.it>

M. Perri and G. Stratta (ASDC) report on behalf of the Swift XRT team:

We have analyzed the first 13.5 ks of Swift-XRT data of the BAT GRB
090205 (Perri et al., GCN Circ. 8884). The data, starting at 2009-02-05
23:04:55 UT and ending at 2009-02-06 09:10:33 UT, is all taken in
Photon Counting (PC) mode.

The best XRT position is the UVOT-enhanced position reported by
Evans et al. (GCN Circ. 8885).

In the time interval T+94s-T+580 s the X-ray light curve can be modeled by
a simple power law with a decay index alpha_1= 1.4 ± 0.3 (90% confidence)
followed by a re-brightening around T+1 ks. After the re-brightnening,
from T+5 ks up to T+30 ks, the light curve decays with a power law
index alpha_2= 0.9 ± 0.2.

The X-ray spectrum is well fit by an absorbed power-law model
with a photon index of 2.0 (+/-0.2) and a column density consistent
with the Galactic one in the direction of the source (7.7e20 cm**-2,
Kalberla et al. 2005). The estimated 3-sigma (2-sigma) upper limit on the
intrinsic column density at z=4.6 (Thoene et al., GCN Circ. 8889) is
4.1e22cm**-2 (2.8e22cm**-2).

Assuming the X-ray emission continues to decline at the same rate, we
predict a 0.3-10 keV XRT count rate of 6e-3 count/s at T+24hr, which
corresponds to an observed 0.3-10 keV flux of ~2e-13 erg/cm**2/s.

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