Skip to main content
Introducing Einstein Probe, Astro Flavored Markdown, and Notices Schema v4.0.0. See news and announcements

GCN Circular 11865

GRB 110402A: Swift-XRT refined Analysis
2011-04-02T11:17:47Z (13 years ago)
Claudio Pagani at U of Leicester <>
C. Pagani (U. Leicester) and T. N. Ukwatta (MSU) report on behalf of
the Swift-XRT team:

We have analysed 6.8 ks of XRT data for GRB 110402A (Ukwatta  et al.
GCN Circ. 11857), from 552 s to 24.7 ks after the  BAT trigger. The
data are entirely in Photon Counting (PC) mode. The enhanced XRT
position for this burst was given by Beardmore et al. (GCN. Circ

The late-time light curve (from T0+6.4 ks) can be modelled with  a
power-law decay with a decay index of alpha=1.3 (+/-0.4).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.31 (+0.25, -0.27). The
best-fitting absorption column is  10.0 (+2.9, -5.6) x 10^20 cm^-2, in
excess of the Galactic value of 1.6 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 3.3 x 10^-11 (4.8 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     10.0 (+2.9, -5.6) x 10^20 cm^-2
Galactic foreground: 1.6 x 10^20 cm^-2
Excess significance: 2.9 sigma
Photon index:	     2.31 (+0.25, -0.27)

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