GCN Circular 11547

G. Stratta (ASDC), V. D'Elia (ASDC), P.A. Evans and M.R. Goad (U. Leicester)
report on behalf of the Swift-XRT team:

Swift began a target of opportunity observation of GRB 110107A
on January 8, 2011 at 15:07 UT, approximately 17.8 hours
after the burst detected by Fermi. The GRB was deteced during a Swift
slew with BAT event capture. Swift data for these
observations utilize Target ID 20157.

The XRT began observing the field at 15:12:43 UT, 64.8 ks after the
Fermi trigger.

Using 2517 s of XRT Photon Counting mode data and 1 UVOT
images, 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 =
299.90910, 41.91400 which is equivalent to:

RA (J2000): �19 59 38.20
Dec (J2000): +41 54 50.3

with an uncertainty of 3.6 arcsec (radius, 90% confidence).
This position is 1.7 arcminutes distant from the BAT position.

This position may be improved as more data are received. �The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

The count rate level is (1.2+/-0.2)10^-2 counts/s.
We cannot state if the source is fading at this stage and
we need to wait for more data.

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

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