GCN Circular 8828

GRB 090118: Swift-XRT observations

B.A. Rowlinson and K.L. Page (U. Leicester) report on behalf of the
Swift-XRT team:
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Swift-XRT began a 6 ks follow-up ToO observation of the likely BAT
Slew Survey GRB 090118 (Copete et al., GCN Circ. 8825
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 ) 25.3 ks after the
start of the slew during which the burst was detected. No X-ray source
is detected within the 3.69 arcmin error circle, with a 3-sigma upper
limit
of 5.8x10^-3 count s^-1.
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However, there is a source just outside the 90% error circle, at a
position of RA, Dec = 49.8276, 18.4148, which is equivalent to:
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RA (J2000) = 03 19 18.62
Dec (J2000) = +18 24 53.3
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with an uncertainty of 7.1 arcsec (radius, 90% confidence). This is a
distance of 260.9 arcsec from the BATSS position.This source has a
count rate of (9.0 +/- 2.2)x10^-3 count s^-1 in the first 1.6 ks of data
and appears to be fading to a count rate of (5.0 +/- 1.4)x10^-3 count
s^-1 in the last 4.2 ks of data.

A spectrum extracted for this source can be fitted with a power-law of
spectral index Gamma = 5.9 (+1.8, -1.4) with an absorbing column density
of 4.6 (+3.1, -2.2) x 10^21 cm^-2, in excess of/consistent with the
Galactic column in this direction of 8.9x10^20 cm^-2.

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