The radio corona of AR Lacertae

¹ Istituto di Radioastronomia del C.N.R., Stazione VLBI di Noto, CP 141 Noto, Italy
² Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania, Italy
³ Dipartimento di Fisica e Astronomia, Università di Catania, Via S. Sofia 78, 95123 Catania, Italy
⁴ Owens Valley Radio Observatory, California Institute of Technology, Big Pine, CA 93513, USA

Corresponding author: C. Trigilio, trigilio@ira.noto.cnr.it

Received: 12 December 2000
Accepted: 12 April 2001

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 Rodonò et al. ([CITE]). 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.