TITLE: GCN CIRCULAR NUMBER: 6603 SUBJECT: GRB070704: FAVOR optical observations DATE: 07/07/06 17:34:41 GMT FROM: Sergey Karpov at SAO RAS 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) 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.