[vsnet-grb-info 5250] GRB 071018: Swift-XRT observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6943
SUBJECT: GRB 071018: Swift-XRT observation
DATE:    07/10/19 16:28:50 GMT
FROM:    Andy Beardmore at U Leicester  <apb at star.le.ac.uk>

A.P. Beardmore, K.L. Page, P.A. Evans, R.L.C. Starling, J.P. Osborne
(U. Leicester) and  H.A Krimm (GSFC/USRA) report on behalf of the
Swift-XRT team:

The Swift-XRT began observing the field of the BAT GRB 071018 
(trigger #294645) at 2007-10-19T00:36, 57 ks after the trigger.
A photon counting mode image containing an exposure time of 4.0 ks
reveals two faint uncatalogued sources:

Source 1 is at RA, Dec (J2000) = 164.51244, 53.82275, which is

RA(J2000)  =  10 58 02.99
Dec(J2000) = +53 49 21.9

with an estimated uncertainty of 6.4 arcsec (radius, 90 percent 
confidence). This is 4.25 arcmin away from the refined BAT position
of Sato et al. (GCN 6933), but outside the quoted BAT 2.7 arcmin
90 percent error circle. Its estimated count rate is (3.2+/-0.9)e-3 
count s^-1.

Source 2 is at RA, Dec (J2000) = 164.58083, 53.82383, which is

RA(J2000)  =  10 58 19.40
Dec(J2000) = +53 49 25.8

with an estimated uncertainty of 7.9 arcsec (radius, 90 percent
confidence). This is 2.37 arcmin away from the refined BAT position
and within its error circle. Its estimated count rate is (2.0+/-0.8)e-3 
count s^-1.

At this stage we cannot tell whether either source is fading and
therefore associated with the GRB. Further observations are
planned by Swift over the weekend.

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