GCN Circular 8405
Subject
GRB 081024: Swift-XRT refined analysis
Date
2008-10-24T20:31:08Z (16 years ago)
From
Matteo Perri at ISAC/ASDC <perri@asdc.asi.it>
G. Stratta (ASDC) reports on behalf of the Swift-XRT team:
We have analysed the first orbit of the XRT data obtained for
GRB 081024 (Stratta et al., GCN Circ. 8398). From T+78 s to T+105 s
after the burst, data were collected in Windowed Timing mode and
then XRT switched to Photon Counting mode. The Enhanced Swift-XRT
position was given by Beardmore et al. in GCN Circ. 8403.
The 0.3-10 keV flux from T+78 s to T+355 s shows a very steep decay with
a possible small re-brightening between ~T+145 s to ~T+205 s. Excluding
the re-brightening and assuming a power law decay, the best fit decay
index is alpha = 3.7 (+0.8,-0.5).
The spectrum of the WT data, with an integration time of 27s, can
be modelled with a power-law model with photon index of 1.6 (+0.6,- 0.3).
The total absorbing equivalent hydrogen column density is consistent
with the Galactic one NH = 7.71E+21 cm^-2 (Kalberla et al. 2005). The
observed (unabsorbed) 0.3-10 keV flux is 4.1(6.1)E-10 erg/cm^-2 s^-1
No source counts are detected after the first orbit, likely due to
the very steep flux decay.
This is an official product of the Swift-XRT team.