Skip to main content
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

GCN Circular 12927

GRB 120211A: Swift-XRT refined Analysis
2012-02-12T00:11:04Z (12 years ago)
Phil Evans at U of Leicester <>
V. Mangano (INAF-IASFPA), D.N. Burrows (PSU), J.A. Kennea (PSU), M.C.
Stroh (PSU), C. Pagani (U. Leicester), A.P. Beardmore (U. Leicester),
P.A. Evans (U. Leicester), A. Melandri (INAF-OAB), B. Sbarufatti
(INAF-OAB/PSU) and E. Sonbas report on behalf of the Swift-XRT team:

We have analysed 6.4 ks of XRT data for GRB 120211A (Sonbas  et al. GCN
Circ. 12920), from 133 s to 13.2 ks after the  BAT trigger. The data
are entirely in Photon Counting (PC) mode. The enhanced XRT position
for this burst was given by Goad et al. (GCN. Circ 12922).

The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=1.47 (+0.33, -0.22). At T+1267 s  the
decay flattens to an alpha of -0.14 (+0.20, -1.36) before breaking
again at T+11.0 ks to a final decay with index alpha=6.6 (+1.4, -4.1).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.29 (+0.21, -0.20). The
best-fitting absorption column is  6.5 (+6.5, -4.8) x 10^20 cm^-2,
consistent with the Galactic value of 1.7 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 5.4 x 10^-11 (5.8 x
10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     6.5 (+6.5, -4.8) x 10^20 cm^-2
Galactic foreground: 1.7 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.29 (+0.21, -0.20)

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