TITLE: GCN CIRCULAR NUMBER: 16022 SUBJECT: GRB 140320C: Mini-GWAC prompt observation DATE: 14/03/21 14:03:44 GMT FROM: L.P. Xin at NAOC J. Y. Wei, L. P. Xin, Y. L. Qiu, J. S. Deng, J. Wang, X. H. Han, C. Wu, H. L. Huang, X. M. Meng, Y. F. Xuan and Y. Xu on behalf of EAFON report: Mini-GWAC system is located at Xinglong observatory, National Astronomical Observatories, China, including 6 mounts and 12 Canon 85/f1.2 cameras. Each mount is equipped with 2 cameras. For each camera, the Apogee U9000X CCD was used, which gives about 400 square degree of FOV. The total field of view of this system is about 5000 sq.deg. The field of INTERGRAL GRB 140320C (Mereghetti et al. GCN 16007) was monitored by Mini-GWAC system continuously during about 2 hrs before and 4 hrs after the burst. The exposure time for each frame is 10 sec. No any new optical counterpart in single frame was detected down to the 5 sigma upper limit of 13.1 mag calibrated by nearby USNO B1.0 R2 mag, at the epoch of prompt emission phase. Combining 5 frames after the burst trigger initially with total exposure time of 50 sec gives a 5 sigma upper limit of 13.7 mag. This message may be cited.