TITLE:   GCN CIRCULAR
NUMBER:  9580
SUBJECT: GRB 090625B: Swift-XRT refined analysis
DATE:    09/06/26 11:44:10 GMT
FROM:    Jirong Mao at INAF-OAB  <jirong.mao@brera.inaf.it>

J. Mao, R. Margutti (INAF-OAB) and C. Guidorzi (U. Ferrara) report
on behalf of the Swift-XRT team:

We have analyzed the first three orbit data (6.9 ks exposure) of the
Swift ToO observation of the INTEGRAL burst GRB 090625B (Gotz, GCN
Circ. 9572).

Swift-XRT observations started at 14:30:13 UT (Mao et al. GCN Circ. 9573),
4ks from trigger.

The source is fading with a best fit simple power law model index
of alpha= 0.6+/- 0.3, confirming its nature of X-ray afterglow.

A spectrum extracted from PC mode data can be modelled with an
absorbed power-law, with Gamma = 3.3 +1.1/-0.8 and NH = (3.7
+2.2/-1.7)x1021 cm^-2. The Galactic column in this direction is
2.1 x 1020 cm-2 (Kalberla et al. 2005).

The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 2.8 x 10-11 (1.8 x 10-10) erg cm-2 count-1.

If the light curve continues to decay with a power-law decay index of 0.6,
the count rate at T+24 hours will be 6.3x10-3 count s-1, corresponding to
an observed (unabsorbed) 0.3-10 keV flux of 1.8x10-13 (1.1x10-12) erg 
cm-2 s-1.

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

[GCN OPS NOTE(26jun09): Per author's request, "Cristiano" was replaced
with "Guidorzi".]