GCN Circular 15361

P. D'Avanzo, A. Melandri, M. G. Bernardini (INAF-OAB), P. A. Evans (U. Leicester)
report on behalf of the Swift-XRT team:

We have analysed 2.8 ks of XRT data for the Fermi/LAT-detected burst:
GRB 131018B (Vianello et al., GCN 15357
Not found
 
 
; Zhang, GCN 15360
Not found
 
 
),  from 83.1
ks to 95.2 ks after the  Fermi/LAT trigger. The data are entirely in
Photon Counting (PC) mode.  An uncatalogued X-ray source is detected
within the Fermi/LAT error circle. The refined XRT position is RA, Dec
= 304.53693, +23.18759 which is equivalent to:

RA (J2000): 20 18 08.86
Dec(J2000): +23 11 15.3

with an uncertainty of 4.9 arcsec (radius, 90% confidence). This
position is 514 arcsec from the Fermi/LAT position.  We cannot
determine at the present time whether the source is fading.


We note the presence of two further sources within the LAT error box.

Source #2 has the following position RA, Dec = 304.41156, +23.16636
which is equivalent to:

RA (J2000): 20 17 38.77
Dec(J2000): +23 09 58.9

with an uncertainty of 5.4 arcsec (radius, 90% confidence). 

Source #3 has the following position RA, Dec = 304.52361 +23.06517
which is equivalent to:

RA (J2000): 20 18 05.67
Dec(J2000): +23 03 54.6

with an uncertainty of 6.0 arcsec (radius, 90% confidence). 

Both sources are present in the Swift-XRT point source catalogue
(D'Elia et al. 2013; A&A 551, A142) and are likely not related with GRB
131018B. 


The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00020308.

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

[GCN OPS NOTE(22oct13): Per author's reuqest, the affiliations of the authors
was corrected.]