[vsnet-grb-info 13590] Swift Trigger 558631: AAO optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  14919
SUBJECT: Swift Trigger 558631:  AAO optical observations
DATE:    13/06/22 13:42:50 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen at iki.rssi.ru>

A. Volnova (IKI), R.Inasaridze (AAO), O. Kvaratskhelia (AAO), V. 
Ayvazian(AAO), Yu. Krugly (IA KhNU),  I. Molotov (KIAM), A. Pozanenko 
(IKI)  report on behalf of  larger GRB follow-up collaboration:

Following trigger Swift #558631 (Barlow et al., GCN 14917) we imaged the 
region of the trigger with   starting on June 21 (UT) 19:54:46. We 
obtained 50 unfiltered images of 50 s exposure. We investigated  a 
combined image (mid time after the Swift trigger 0.75693 days) and 
within BAT error circle (Barlow et al., GCN 14917) found one bright 
source which is not catalogued in USNO-B1.0 but barely visible in DSS2 
Red image. Coordinates of the source is (J2000) 18:07:13.13 -22:17:14.4. 
It is apparent that the source is not coincident with known X-ray source 
SAX_J1806.5-221. Brightness of the source is 17.09 +/- 0.03 calibrating 
against nearby USNO-B1.0 stars (R2).

At present time it is not clear if the source is related to the Swift 
#558631 trigger. The source also can be a new cataclysmic variable with 
magnitude of the outburst of ~3m.

A finding cahart can be found in
http://grb.rssi.ru/Swift_558631/Swift_558631_chart.png