TITLE:   GCN CIRCULAR
NUMBER:  9525
SUBJECT: Swift XRT observations of GRB 090531A 
DATE:    09/06/18 16:21:56 GMT
FROM:    Boris Sbarufatti at INAF-IASF-Pa  <sbarufatti@ifc.inaf.it>

B. Sbarufatti, V. Mangano (INAF-IASFPA) on behalf of the Swift-XRT team.

The XRT onboard Swift observed the field of GRB 090531A on 2009 June  
10 and 2009 June 17, after it came outside the Moon observing  
contstraint, for a total exposure of 35.5 ks in Photon Counting mode.

Three significant sources are detected inside the initial BAT error  
circle (Stamatikos, et al., GCN circ. 9454). Two of them, detected at  
a level of 1.2E-3 counts/s and 9.0E-4 counts/s, are compatible with a  
stable count-rate and are found outside the BAT refined error circle  
(Sakamoto, et al., GCN circ. 9460). The third source, detected at a  
level of 6.5E-4 counts/s is too faint to estimate if it is fading or  
not, and it is found just inside the BAT refined error circle, at a  
distance of 64.8 arcsec from the BAT refined position. Its coordinates  
are RA,Dec = 178.65539, +7.81671 which is:

RA(J2000)  =  11h 54m 37.29s
Dec(J2000) = +07d 49' 00.2"

with an uncertainty of 4.8 arcsec (radius, 90% confidence).

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