[vsnet-grb-info 4854] GRB 070628: Watcher Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6586
SUBJECT: GRB 070628: Watcher Observations
DATE:    07/06/28 21:56:11 GMT
FROM:    Gary Melady at UCD  <gmelady at bermuda.ucd.ie>

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). 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) 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.

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