TITLE:   GCN CIRCULAR
NUMBER:  30547
SUBJECT: GRB 210724A: Corrected Swift-XRT enhanced position
DATE:    21/07/29 15:25:48 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P.A. Evans (U. Leicester) and P. D'Avanzo (INAF-OAB) report on behalf of 
the Swift-XRT team.

The XRT position of GRB 210724A reported in GCN Circ. 30515 was 11" from 
the position of the optical candidate found by de Ugarte Postigo et al. 
(GCN Circ. 30511). Unusually, this position underwent significant 
variation during the normal revisions after each data downlink. 
Investigation has revealed a rare local minimum issue during the first 
XRT image, which has now been fixed.

The best XRT position is RA, Dec = 227.41461, -6.29070 which is 
equivalent to:

RA (J2000): 15h 09m 39.51s
Dec(J2000): -06d 17' 26.5"

with an uncertainty of 3.0 arcsec (radius, 90% confidence). This 
position is 1.1" from the optical position of de Ugarte Postigo et al.

We apologise for the confusion caused by this rare glitch, which 
coincided with the author's vacation (Murphy et al).

As ever, the most recent version of the position can be found online at:
https://www.swift.ac.uk/xrt_positions/01061482/


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