Skip to main content
Testing. You are viewing the public testing version of GCN. For the production version, go to
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

GCN Circular 11074

GRB 100807A: Swift XRT refined analysis
2010-08-08T00:29:22Z (14 years ago)
Dirk Grupe at PSU/Swift-XRT <>
D. Grupe (PSU) reports on behalf of the Swift-XRT team:

We have analyzed 9.7 ks of XRT data for GRB 100807A (Grupe  et al.
GCN Circ. 11067), from 125 s to 24882 s after the  BAT trigger. The
data comprise 36 s in Windowed Timing (WT) mode with the remainder
in Photon Counting (PC) mode. The light curve can be modeled
with  a broken power-law model. After an initial flare the light
curve decays with a slope of 6.4+0.6-1.9. The light curve breaks at
173+/-10s followed by a flatter decay slope of 0.82+/-0.08.

A spectrum formed from the WT mode data can be fitted with an
absorbed power-law with a photon spectral index of 2.12 (+/-0.22).
The best-fitting absorption column is consistent with the Galactic
value of 3.3 x 10^21 cm^-2 (Kalberla et al. 2005). A fit to the pc
mode data is also consistent with the Galactic absorption column
density, but the spectrum is slightly flatter with  a photon index
of 1.79+/-0.37. The counts to observed (unabsorbed) 0.3-10 keV flux
conversion factor deduced from the WT spectrum  is 4.38 x 10^-11
(7.54 x 10^-11) erg cm^-2 count^-1.

If the light curve continues to decay with a power-law decay index
of 0.8, the count rate at T+48 hours will be in the order of
1.3 x 10^-3 count s^-1, corresponding to an observed (unabsorbed)
0.3-10 keV flux of 5.7 x 10^-14 (9.8 x 10^-14) erg cm^-2 s^-1.
Note that we are currently in the plateau phase which is followed by
a steeper decay slope.

The results of the XRT-team automatic analysis are available at

This circular is an official product of the Swift-XRT team.
Looking for U.S. government information and services? Visit