GCN Circular 8543
Subject
GRB 081121: Swift-XRT refined analysis
Event
Date
2008-11-22T11:43:57Z (17 years ago)
From
Olivier Godet at U.of Leicester <og19@star.le.ac.uk>
O. Godet (U Leicester) and S. Oates (UCL-MSSL) on behalf the Swift-XRT
team:
The Swift-XRT started observing the field of GRB 081121 (trigger number
335105, Oates et al., GCN Circ. 8537) at 2008-11-21 20:35:32 UT, 2.8 ks
after the trigger. The best XRT position is the UVOT-enhanced position
reported by Goad et al. (GCN Circ. 8541). This position is consistent with
the optical positions reported by the Swift-UVOT and ROTSE III (Oates et
al., GCN Circ. 8538; Yuan et al., GCN Circ. 8536).
The X-ray light curve presently spans 4.2 ks of photon counting (PC) mode
data from T+2.8 ks to T+16 ks. The light curve shows an initial decay with
a slope of 1.11 +0.06/-0.05 up to at least ~T+17 ks, followed by a steep
decay up to ~T+20 ks and then a flatter decay with a slope of 0.25
+0.62/-0.13.
The PC X-ray spectrum from the same interval can be well fit by an absorbed
power-law with a photon index of 1.99 +0.10/-0.09 and a column density of
(9.7 +2.2/-2.0) x 10^20 cm^-2 (the Galactic value is 4.0 x 10^20 cm^-2 in
the direction of the burst). The observed 0.3-10.0 keV flux is (7.1
+/-0.4) x 10^-11 erg cm^-2 s^-1 which corresponds to an unabsorbed flux of
(9.0 +0.2/-0.5) x 10^-11 erg cm^-2 s^-1.
If the burst continues on the current plateau phase, the predicted count
rate at T+1 day would be approximately 1.2 x 10^-1 count s^-1.
This is an official product of the Swift-XRT team.