L. P. Xin, J. Y. Wei, Y. L. Qiu, E. W. Liang, X. H. Han,
Y. Xu, L. Huang, Y. G. Yang, X. M. Meng, H. B. Cai,
J. Wang, C. Wu, J. S. Deng and H. L. Li report:
The field of SWIFT GRB 160104A (Melandri et al. GCN 18815)
was monitored by Mini-GWAC system continuously
during about 1.5 hrs before and 1 hrs after the burst trigger time.
The exposure time for each frame is 10 sec.
No any new optical counterpart (Guidorzi et al., GCN 18816;
Saito GCN 18817; Xin et al., GCN 18823) in single frame
was detected down to the 5 sigma upper limit of 12.3 mag
during our observations, calibrated by nearby USNO B1.0 R2 mag,
at the epoch of prompt emission phase.
Combining 5 frames during and after the burst trigger initially with a total
exposure time of 50 sec gives a 5 sigma upper limit of 12.8 mag.
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.
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