Properties of Stellar Magnetospheres Deduced from Radio Observations of Close Binaries
Recent observations of circular polarization and angular size of nonthermal radio emission from close binary systems (mainly of the RS CVn class) provide strong constraints on possible models for the emission region. The ‘non-flare’ observations are consistent with gyrosynchrotron emission from an extended coronal region associated with a single active star. The radio data are consistent with helmet structure magnetic field geometries containing trapped plasma in large torus shaped regions. Detailed numerical models must include the effects of stellar winds, refraction in the stellar atmosphere, rapid rotation of the active star, and accurate numerical approximations for the emissivity and absorption coefficient for gyro-synchrotron emission at low harmonic numbers.
Over the past five years, a large corpus of rich, detailed radio observations of single and multiple stellar systems has been published. These observations have been made possible largely through the high flux and spatial sensitivity of the VLA and Mklll VLB arrays. The radio data, when combined with X-ray observations from the HEAO and EXOSAT space telescopes, have provided our first detailed look at the extended coronae of stars other than the sun. Although observations at both wavelengths have been made of a large variety of stars (Dulk 1985), in this paper we will be concerned only with close, late-type binaries principally of the RS CVn class (Hall, 1981), because we believe the observations of this class provide the clearest description of the irrespective coronae.
KeywordsCircular Polarization Dead Zone Stellar Wind Close Binary System Active Star
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