In the long-term multi-frequency monitoring program of the microquasars with RATAN-600 we discovered the giant flare from X-ray binary Cyg X-3 on 13 September 2016 .
It happened after 2000 days of the ’ quiescent state ’ of the source passed after the former giant flare ( \sim 18 Jy ) in March 2011 .
We have found that during this quiet period the hard X-ray flux ( Swift/BAT , 15-50 keV ) and radio flux ( RATAN-600 , 11 GHz ) have been strongly anti-correlated .
Both radio flares occurred after transitions of the microquasar to a ’ hypersoft ’ X-ray state that occurred in February 2011 and in the end of August 2016 .
The giant flare was predicted by us in the first ATel ( Trushkin et al .
( 2016 ) ) .
Indeed after dramatic decrease of the hard X-ray Swift 15-50 keV flux and RATAN 4-11 GHz fluxes ( a ’ quenched state ’ ) a small flare ( 0.7 Jy at 4-11 GHz ) developed on MJD 57632 and then on MJD 57644.5 almost simultaneously with X-rays radio flux rose from 0.01 to 15 Jy at 4.6 GHz during few days .
The rise of the flaring flux is well fitted by a exponential law that could be a initial phase of the relativistic electrons generation by internal shock waves in the jets .
Initially spectra were optically thick at frequencies lower 2 GHz and optically thin at frequencies higher 8 GHz with typical spectral index about -0.5 .
After maximum of the flare radio fluxes at all frequencies faded out with exponential law .