1994A&A...286..181V

We report on the detection of flare and quiescent emission from the RS CVn system II Peg at 360 and 609 MHz. The radio flare at 360 MHz lasted for half an hour and showed strong, spikelike variability on time scales probably shorter than the instrumental time resolution of one minute. The emission is coherent and must occur at or near the local plasma frequency in the source. Electron cyclotron maser emission can be excluded because of the low magnetic field strengths required at this observing frequency. Plasma emission by a moving exciter (beam or shock) can be excluded on base of the available spectral information. Plasma maser emission originating in a collection of double layers is consistent with the available spectral information. We discuss the role of free-free opacity which can dramatically lower the observed brightness temperature and influence the shape of the observed spectrum. The flare at 609 MHz was only observed during the decay phase. This flare has the typical characteristics of the incoherent radio flares previously observed in RS CVn systems except for an unusual high percentage of circular polarization (90%) which on a timescale of a few hours decreases to approximately 50%. We discuss the most likely emission mechanisms but are not able to provide a definite conclusion concerning the nature of the emission at 609 MHz.