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 10674

GRB 100424A: Swift-XRT refined analysis
2010-04-25T04:13:36Z (14 years ago)
Michael Stroh at PSU/Swift <>
M. C. Stroh, D. Grupe and E. A. Hoversten (PSU) report on behalf of the Swift-XRT team:

We have analysed 641 s of XRT data for GRB 100424A (Hoversten  et al.
GCN Circ. 10667), from 126 s to 769 s after the  BAT trigger. The data
comprise 509 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The light curve can be modelled with a
series of power-law decays. The initial decay index is alpha=0.63
(+/-0.14). At T+288 s the decay steepens to an alpha of 1.41 (+0.27,
-0.19) before breaking again at T+526 s to a final decay with index
alpha=2.8 (+0.9, -0.6).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.26 (+/-0.06). The
best-fitting absorption column is 1.62 (+0.22, -0.21) x 10^21 cm^-2,
in excess of the Galactic value of 2.3 x 10^20 cm^-2 (Kalberla et al.
2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 5.8 x 10^-11 (6.5 x 10^-11) erg
cm^-2 count^-1.

If the light curve continues to decay with a power-law decay index of
2.8, the count rate at T+24 hours will be 5.1 x 10^-6 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.0 x
10^-16 (3.3 x 10^-16) erg cm^-2 s^-1.

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