GCN Circular 10342

B. Sbarufatti, R. Margutti (INAF/OAB) and M. De Pasquale (UCL-MSSL)  
report on behalf of the Swift-XRT team:

We have analysed 5.5 ks of XRT data for GRB 100117A (De Pasquale et  
al. GCN Circ. 10336
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 ), from 69 s to 18.9 ks after the BAT trigger. The  
data comprise 180 s in Windowed Timing (WT) mode with the remainder in  
Photon Counting (PC) mode.

The best position is the SPER UVOT enhanced position: RA,Dec =  
11.2690, -1.5949
(degrees) which is equivalent to:
RA (J2000) = 00 45 4.56
Dec (J2000) = -01 35 41.7

with an uncertainty of 2.4 arcsec (radius, 90% containment).
This location is 50.8 arcseconds from the BAT ground position, inside  
the BAT
error circle.

After the initial flaring activity the light curve can be modeled with  
a power-law decay with a decay index of alpha=3.5 (+/-0.2). The  
afterglow is not detected after the first snapshot of data (ending 500  
s after the trigger), with an upper limit of 5E-3 count/sec at ~12 ks  
after the trigger

The spectrum formed from the WT mode data can be fitted with an  
absorbed power-law with a photon spectral index	of 1.6 (+/-0.13). The  
best-fitting absorption column is 1.2 (+/-0.4) x 10^21 cm^-2, in  
excess of the Galactic value of 2.7 x 10^20 cm^-2 (Kalberla et al.  
2005). The observed (unabsorbed) 0.3-10 keV flux is 4.14 (4.84) x  
10^-10 erg cm^-2 s^-1.

The spectrum formed from the PC mode data can be fitted with an  
absorbed power-law with a photon spectral index	of 2.3 (-0.5+0.6). The  
best-fitting absorption column is 1.1 (+1.3-0.9) x 10^21 cm^-2,  
slightly in excess of the Galactic value of 2.7 x 10^20 cm^-2  
(Kalberla et al. 2005). The observed (unabsorbed) 0.3-10 keV flux is  
2.40 (3.54) x 10^-12 erg cm^-2 s^-1.

The count-rate to flux conversion factor is 6.0E-11 erg cm^-2 count^-1.

The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00382941 
.

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