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GCN Circular 8767

GRB 090102: Swift XRT refined analysis
2009-01-02T16:30:08Z (15 years ago)
Vanessa Mangano at INAF-IASFPA <>
V. Mangano, V. La Parola, B. Sbarufatti (INAF-IASF PA)
report of behalf the Swift XRT team:

We have analysed 6 orbits of Swift XRT data of GRB 090102
(Mangano et al. GCN Circ. 8762), consisting of 241 s in WT mode
and 6.7 ks in PC mode.

The XRT observation started 393 s after the trigger.
The XRT light curve is well fitted by a single power-law
with slope -1.32 +/- 0.01, and if decaying at this rate
the source will reach a count rate level of 0.02 counts/s
after one day.

The WT spectrum is well fitted by an absorbed power-law
with photon index 1.7 +/- 0.1, Galactic NH = 4.0e20 cm^-2
(Kalberla et al. 2005) and intrinsic absorption column of
(3.8 +/- 2.0) e21 cm^-2 at the measured redshift z = 1.547
(De Ugarte Postigo et al. GCN Circ. 8766).
The average observed [unabsorbed] flux during the WT observation
is 6.2e-10 [7.2e-10] erg cm^-2 s^-1.

The PC spectrum, extracted from about T+630 s to T+25 ks,
is also well fitted by an absorbed power law with photon
index 1.8 +/- 0.1, Galactic NH = 4.0e20 cm^-2 and
and intrinsic NH = (7.0 +/- 2.0) e21 cm^-2 at z = 1.547.
The average observed [unabsorbed] flux during the PC observation is
2.8e-11 [3.5e-11] erg cm^-2 s^-1.

The rate to flux conversion factor is 1.3e-10 erg cm^-2 counts^-1.

This is an official product of the Swift XRT team.
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