[vsnet-grb-info 3610] GRB 060813: Swift XRT refined analysis
GCN Circulars
gcncirc at capella.gsfc.nasa.gov
Mon Aug 14 19:19:14 JST 2006
TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 5444
SUBJECT: GRB 060813: Swift XRT refined analysis
DATE: 06/08/14 10:17:51 GMT
FROM: Alberto Moretti at Obs Brera Merate <alberto.moretti at brera.inaf.it>
A. Moretti (INAF-OAB), C. Guidorzi (Univ. Bicocca & INAF-OAB),
P. Romano (INAF-OAB) report on behalf of the Swift-XRT team:
We have analysed the first 4 orbits of Swift-XRT data obtained for GRB
060813 (trigger number 224364). The data consist of 611 s in Windowed
Timing (WT) mode, starting 76 seconds after the BAT trigger and 7 ks
in Photon Counting (PC) mode. Using PC data we obtain a refined
position of:
RA(J2000) = 07 27 35.36
Dec(J2000) = -29 50 54.2
with an estimated uncertainty radius of 3.5 arcsec (90% containment).
This is at 27" from the refined BAT position (Cummings et al., GCN
Circ. 5443).
The light-curve shows a shallow decay with alpha = 0.58+/- 0.05, in
the first part up to a break at time=861+/-180 s. After the break
data show a decline with alpha = 1.10+/- 0.05.
The spectrum formed from all the WT data before the light-curve break
can be modelled with a power-law of photon index Gamma = 1.98 +/-
0.08, with an absorbing column of NH = (4.4 +/- 0.4)e21 cm^-2
marginally consistent with the Galactic value of 3.1e21 cm^-2.
The spectrum formed from the PC data after the light-curve break is
maginally consistent with the pre-break spectrum: it can be modelled
with a power-law of photon index Gamma = 1.80 +/- 0.10, with an
absorbing column of NH = (3.2 +/- 0.5)e21 cm^-2.
Assuming the light-curve continues to decay with alpha ~ 1.10, the
count rate at 24 hours is predicted to be 0.023 count s^-1. This
corresponds to an observed (unabsorbed) flux of 1.4e-12 (1.9e-12)
erg cm^-2 s^-1.
This circular is an official product of the Swift-XRT team.
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