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Astron. Astrophys. 359, 1035-1041 (2000)

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VLA observation of dMe stars

G. Leto *  1, I. Pagano[FORMULA]  1, J.L. Linsky 2, M. Rodonò 1,3 and G. Umana 4

1 Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania, Italy
2 JILA, University of Colorado and NIST, Boulder CO, 80309-0440, USA
3 Dipartimento di Fisica e Astronomia, Università di Catania, Via S. Sofia 78, 95123 Catania, Italy
4 Istituto di Radioastronomia C.N.R., Stazione VLBI, 96017 Noto (SR), Italy

Received 14 January 2000 / Accepted 25 May 2000

Abstract

We present new VLA radio observations of a sample of dMe stars in X, U, K, and Q bands (from 8.4 to 43 GHz) obtained during an observing campaign in 1996 April-June. The aim of the project was to determine the spectral energy distributions of late-type dwarf flare stars to investigate the possible existence of an inversion of the spectrum slope at frequencies higher than 8 GHz. We also tried to constrain the possible emission mechanism at radio frequencies. We have detections in X band (8.4 GHz), for three sources (UV Cet, V 1054 Oph, and EV Lac), while all of our other measurements are upper limits. We discuss how the weak radio emission of some sources (e.g. AU Mic) and the coronal plasma properties deduced from X-ray observations constrain the coronal magnetic field properties.

Key words: stars: activity – stars: coronae – stars: late-type – stars: variables: general – radio continuum: stars

* Visiting Astronomer at JILA, University of Colorado, Boulder CO, 80309-0440 USA

Send offprint requests to: G. Leto (gleto@ct.astro.it)

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© European Southern Observatory (ESO) 2000

Online publication: July 13, 2000
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