The radio corona of AR Lacertae

Abstract

We present multifrequency VLA and VLBA observations at 8.4 GHz of the RS CVn system {AR Lac}, that were performed in autumn 1997 simultaneously with X-ray observations obtained from Rodonòet al. (\cite{Rodono}). Our VLBA data indicate a resolved source with dimension close to the system separation, while the study of the flux density curve reveals a small amplitude outside of the eclipse variability. The derived five-frequencies spectra, combined with the size information from VLBA data, are compared with gyrosynchrotron emission from a two component structured source. A comparison with the results of the X-ray observations allow us to exclude the possibility that a thermal gyrosynchrotron is responsible for the radio emission, but it is compatible with the hypothesis of co-spatial X-ray and radio emitting sources.