GCN Circular 7608
Subject
GRB 080413B: Swift XRT refined analysis
Event
Date
2008-04-13T18:55:01Z (18 years ago)
From
Eleonora Troja at INAF-IASFPA <nora@ifc.inaf.it>
E. Troja (U. Leicester/INAF-IASFPa) and M. Stamatikos (NASA/ORAU)
report on behalf of the Swift-XRT team:
We have analysed 9.9 ks of Swift XRT data for GRB 080413B (Stamatikos et
al. GCN Circ. 7598), from T0+134 s to T0+20.1 ks.
The data set consists of 376 s exposure in Windowed Timing (WT) mode
followed by 9.5 ks exposure in Photon Counting (PC) mode.
By using orbits 2-4 of PC data [from T0+6.0 ks to T0+20.1 ks]
in order to avoid pile-up effects, we derive an XRT refined position
RA (2000) = 21h 44m 34.43s = 326.1435 d
Dec (2000) = -19d 58' 52.9" = -19.9814 d
with an uncertainty of 3.7 arcsec (90% containment). This position
is 3.6 arcsec from the UVOT candidate afterglow (GCN Circ. 7598),
and 3.4 arcsec from the source reported in Kruehler et al. (GCN Circ.
7599).
The X-ray light curve is well fitted by a simple power-law, with a
decay slope of 0.88 +/- 0.06.
A spectrum obtained from the WT mode data, from T0+135 s to T0+511 s,
can be modelled with an absorbed power-law with a photon index of
2.05 +/- 0.10 , and a redshifted absorbing column of (0.32 +/- 0.13)
x 10^22 cm^-2 at a redshift of z=1.1 (Vreeswijk et al. GCN Circ 7601)
in addition to the Galactic column of 3.06 x 10^20 cm^-2 (Kalberla et
al. 2005). The observed (unabsorbed) 0.3-10 keV flux in this spectrum is
1.79 x 10^-10 (2.13 x 10^-10) erg/cm^2/s.
The PC spectrum of the first four orbits, from T0+512 s to T0+20.1 ks,
can be fit by an absorbed power-law model with photon index 1.93 +/-
0.08 and a column density consistent with the WT spectrum.
All the reported errors are at the 90% confidence level.
If the source continues to decay at the present rate, we predict a count
rate of 0.035 count/sec at T0+24 hours, which corresponds to a 0.3-10 keV
observed (unabsorbed) flux of 1.6 x 10^-12 (1.8 x 10^-12) erg/cm^2/s.
This circular is an official product of the Swift-XRT team.