GCN Circular 7208
Subject
GRB 080123: Swift-XRT refined analysis
Date
2008-01-23T17:24:42Z (16 years ago)
From
Boris Sbarufatti at INAF-IASF-Pa <sbarufatti@ifc.inaf.it>
V. Mangano, B. Sbarufatti (INAF-IASF PA), T. N. Ukwatta (GSFC/GWU),
and D. N. Burrows (PSU) report on behalf of the Swift XRT team:
We have analyzed the XRT data collected during the first three
orbits of observation of GRB 080123 (Ukwatta et al., GCN Circ. 7203).
We have 124 s of exposure in WT mode (from T+108 to T+224 s)
and 7.1 ks in PC mode.
The initial XRT on-board position was centered on a cosmic ray hit.
This position was retracted. The XRT position reported in GCN Circ.
7203 was obtained from the first downlinked data, but we note that the
error circle given in this circular erroneously ignored the systematic
component and was therefore much too small. The new, refined position
of the XRT afterglow is
22h 35m 46.6s, -64d 54' 03.8" (J2000)
with an error circle radius of 3.9" (90% confidence).
As reported by Osborne et al. (GCN Circ. 7204), the UVOT-enhanced
astrometric position is RA, Dec = 338.94226, -64.90090 which is
equivalent to:
RA (J2000): 22h 35m 46.1s
Dec (J2000): -64d 54' 03.24"
with an uncertainty of 2.1 arcsec (radius, 90% confidence).
The X-ray light curve of the source shows a doubly broken
power law behaviour, with an initial decay with slope 1.7 +/- 0.2,
a first break at T+203 +/- 10 s, a second decay phase with
slope 6.9 +/- 0.4, a second break at T+436 +/- 250 s
and a third decay phase with slope 1.2 +/- 0.3.
If decaying at this rate the source will be at the level of
9.0e-5 counts/s at T+24 hr.
The WT spectrum is well fitted by an absorbed power law with
photon index 1.64 +/- 0.09, while the PC spectrum can be
fitted by a power law with photon index of 2.1 +/- 0.2.
Both spectra are consistent with an absorption column
of (8.1 +/- 2.4)e20 cm^-2, in excess with respect to the
Galactic absorption along the line of sight (2e20 cm^-2,
Kalberla et al. 2005).
The observed (unabsorbed) flux in the 0.3-10 keV band
is 7.0e-10 (7.9e-10) erg cm^-2 s^-1 for the WT spectrum
and 1.1e-12 (1.4e-12) erg cm^-2 s^-1 for the PC spectrum.
This circular is an official product of the Swift-XRT team.