[AAVSO-HEN] GRB 090118: Swift-XRT observations

[grb at aavso.org]

The following is a GCN Circular circulated via the AAVSO network.
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TITLE:   GCN CIRCULAR
NUMBER:  8828
SUBJECT: GRB 090118: Swift-XRT observations
DATE:    09/01/19 17:41:00 GMT
FROM:    Antonia Rowlinson at U.of Leicester  <bar7 at star.le.ac.uk>

GRB 090118: Swift-XRT observations

B.A. Rowlinson and K.L. Page (U. Leicester) report on behalf of the
Swift-XRT team:
 
Swift-XRT began a 6 ks follow-up ToO observation of the likely BAT
Slew Survey GRB 090118 (Copete et al., GCN Circ. 8825) 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.
 
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:
 
RA (J2000) = 03 19 18.62
Dec (J2000) = +18 24 53.3
 
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.