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Issue A&A
Volume 373, Number 1, July I 2001
Page(s) 181 - 189
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20010566



A&A 373, 181-189 (2001)
DOI: 10.1051/0004-6361:20010566

The radio corona of AR Lacertae

C. Trigilio1, C. S. Buemi1, G. Umana1, M. Rodonò2, 3, P. Leto1, A. J. Beasley4 and I. Pagano2

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

(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. (1999). 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.


Key words: stars: coronae -- radio continuum: stars -- stars: binaries: close -- stars: individual: AR Lac -- stars: binaries: general -- techniques: interferometric

Offprint request: C. Trigilio, trigilio@ira.noto.cnr.it

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© ESO 2001


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