GCN Circular 6603

S. Karpov, G. Beskin (Special Astrophysical Observatory of Russian Academy of
   Sciences, Russia), S. Bondar, E. Ivanov, E. Katkova (Research Institute for 
Precision Instrumentation, Russia), A. Pozanenko (Space Research Institute, Russia)

report on behalf of the FAVOR team:

The field of GRB 070704 (Sakamoto et al, GCN 6594
Not found
 
 
) has been observed by the
FAVOR (FAst Variability Optical Registrator) wide-field fast camera (15 cm
diameter, 16x21 deg FOV) located in Russia, North Caucasus, near 6-m telescope
since UT 20:05:17 (40 seconds before BAT trigger, 25 seconds after actual burst
onset), during the event and for 20 minutes after it with 7.5 frames per second
acquisition rate (0.128 s frame exposure). The event occured on the edge of CCD
detector and has been affected by the image distortion. The authomatic data
reduction and transient detection pipeline, based on the inspection of each
pixel statistical properties in time, has not detected any transient event at
the XRT position of the source with the limiting magnitude of 10.8 (3-sigma) in
the unfiltered light close to V on a single frame.

We performed additional study of the data on T-40s - T+142s time interval
(i.e. prior to Swift/UVOT observations). Combining the sets of 100 consecutive
images we obtained an upper limit of 13.0 m (3-sigma) on the optical emission
over this time span with temporal resolution of 12.8 s.

The message may be cited.