Study of the Microquasar Cygnus X-3 with the RATAN-600 Radio Telescope in Multi-Azimuth Observing Mode

We have been carrying out daily observations of bright microquasars at 1.2–20 GHz with the Northern sector of the RATAN-600 radio telescope for more than ten years. During the 2019–2021 observations we detected bright flares, which we call giant flares because fluxes reach record levels—above 20 Jy—during these events. In this paper we report the results of intraday variations of the microquasar Cygnus X-3 in multi-azimuth observations made with the ‘‘Southern sector with a flat-sheet reflector’’ during giant flares of Cygnus X-3. These were the first such observations made simultaneously at several frequencies on a short time scale (10 minutes). Observational data consists of 31 measurement made within 2.7 hours of the culmination of the object. We are the first to discover the evolution of the spectrum of the flare emission of Cygnus X-3 on a time scale comparable to the orbital period of the binary. The measurement data allowed us to determine the temporal and spectral parameters of radio emission, which are typical for synchrotron flare emission in relativistic jets. Evolution of the radio emission of X-ray binaries on short time scales is a key to understanding the formation of jet outbursts in the process of mass accretion of the matter of the donor star onto the relativistic object.