GCN Circular 6586

Gary Melady (University College Dublin), John French (UCD),
Petr Kubanek (GACE Valencia), Martin Jelinek (IAA CSIC Granada)

report on behalf of the Watcher collaboration:

The Watcher 40cm robotic telescope, located at Boyden Observatory,
South Africa, responded to Swift Trigger 283320 (GRB 070628, Holland et al. 
GCN 6584
Not found
 
 
). when the dome opened at 15:17:29 UT, 36.43 minutes after the
trigger. However the bright evening sky rendered the earliest images
unusable. 

An unfiltered 60s exposure taken under twilight conditions at 16:12:48 UT, 
91.76 minutes after the Swift trigger, showed no new source in the UVOT 
error box (as reported by Gronwall et al., GCN 6585
Not found
 
 
) down to an R-band 
limiting magnitude of approx 16.2 (in comparison to USNO-B1).

We combined 27 subsequent 60s exposures to create a 1620s unfiltered image with 
an exposure mid-time of 16:28:05 (108.05 minutes after the trigger). The later 
images were taken at high air mass as the target was setting. This shows no new 
source in the error box down to an R-band limiting magnitude of approx 17.2.

The target set at our location at 18:20 UT so no further observations will be made.

This message may be cited.