GCN Circular 14300

J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), C. Pagani (U.
Leicester), B. Sbarufatti (INAF-OAB/PSU), G. Stratta (ASDC), P.
D'Avanzo (INAF-OAB), J.A. Kennea (PSU), M.C. Stroh (PSU), D.N. Burrows
(PSU) and B.P. Gompertz report on behalf of the Swift-XRT team:

We have analysed 9.1 ks of XRT data for GRB 130313A (Gompertz  et al.
GCN Circ. 14293
Not found
 
 
),  from 85 s to 18.7 ks after the  BAT trigger. The
data are entirely in Photon Counting (PC) mode. The refined XRT
position is RA, Dec = 236.41004, -0.36897 which is equivalent to:

RA (J2000): 15 45 38.41
Dec(J2000): -00 22 08.3

with an uncertainty of 4.8 arcsec (radius, 90% confidence). We cannot
determine at the present time whether the source is fading.

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.6 (+3.4, -4.0). The
best-fitting absorption column is  consistent with the Galactic value
of 5.9 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 7.0 x 10^-11 (7.8 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     0 (+1.7, -0) x 10^23 cm^-2
Galactic foreground: 5.9 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.6 (+3.4, -4.0)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00550906.

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