1995A&A...295..123S

During simultaneous observations of four flare stars between the Stephanion Observatory (optical-U or Bband) and Effelsberg (radio-2695MHz), several strong optical flares were detected without counterpart at radio wavelengths (at a level >60mJy). This result suggests that the optical and radio flares are produced by different mechanisms. The radio flares reported in the past from these and other flare stars may be related to the recently detected phenomenon of short time optical variability. Some reported radio flares could also be attributed to the existence of other radio sources which happen to be in the primary beam of the radio telescopes. Mapping the area around seven well known flare stars has revealed in fact the existence of several strong radio sources in their vicinity. Most of these sources appear to be extragalactic.