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GCN Circular 8725

GRB 081224: Swift-XRT observation
2008-12-25T10:17:22Z (16 years ago)
Kim Page at U.of Leicester <>
K.L. Page and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT 

Swift performed a Target of Opportunity follow-up observation of the Fermi 
GBM and LAT burst GRB 081224 (Wilson-Hodge et al., GCN Circ. 8723), 
starting 18 ks after the trigger. 

There is a faint X-ray source (~6.7x10^-3 count s^-1) within the XRT field 
of view, detected in the 3.6 ks of data collected so far. Using 1193 s of 
XRT Photon Counting mode data and 1 UVOT image, we find an astrometrically 
corrected X-ray position (using the XRT-UVOT alignment and matching UVOT 
field sources to the USNO-B1 catalogue): RA, Dec = 213.1494, 74.1999, 
which is equivalent to:

RA (J2000):   14 12 35.85
Dec (J2000): +74 11 59.5

with an uncertainty of 3.4 arcsec (radius, 90% confidence).

However, we note that the uncertainty on the LAT position (36 arcmin) is 
larger than the XRT field of view, so Swift has not observed the complete 
error circle. We also cannot say whether the XRT source is fading at this 

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