TITLE:   GCN CIRCULAR
NUMBER:  14555
SUBJECT: GRB 130502B: Swift-XRT refined Analysis
DATE:    13/05/04 13:30:51 GMT
FROM:    Andrea Melandri at INAF-OAB  <andrea.melandri@brera.inaf.it>

A. Melandri (INAF-OAB) and S. Immler (NASA/CRESST/GSFC) report on  
behalf of the Swift-XRT team:

We have analysed  8.3 ks of XRT data for the Fermi/LAT-detected burst:  
GRB 130502B (Kocevski  et al. GCN Circ. 14532), from 55.1 ks to 101.8  
ks after the Fermi/LAT trigger.

The object dectected in the first 3.4 ks of XRT data (Melandri &  
Immler GCN Circ. 14540) is now clearly fading. The light curve can be  
modelled with  a power-law decay with a decay index of alpha=1.52  
(+/-0.25).

A spectrum formed from the PC mode data can be fitted with an absorbed  
power-law with a photon spectral index of 1.89 (+/-0.20). The best- 
fitting absorption column is  1.73 (+0.78, -0.71) x 10^21 cm^-2, in  
addition to the Galactic value of 1.1 x 10^21 cm^-2 (Kalberla et al.  
2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion  
factor deduced from this spectrum  is 4.3 x 10^-11 (6.3 x 10^-11) erg  
cm^-2 count^-1.

A summary of the PC-mode spectrum is thus:
Galactic foreground:    1.1 x 10^21 cm^-2
Intrinsic column:         1.73 (+0.78, -0.71) x 10^20 cm^-2
Photon index:	         1.89 (+0.21, -0.20)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00020266.

This circular is an official product of the Swift-XRT team.