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    On the Coronal Activity of the RS CVn-Type Binaries
    (1999) Demircan, Osman; Ak, Hasan
    We re-analysed the behaviour of coronal activity of the RS CVn-type binaries as a function of stellar and orbital parameters. Highly significant correlations were found between the x-ray luminosity Lx and the stellar radius R, the Roche lobe filling fraction ?, and the Alfven radius RA. The correlations of Lx with the mass M, the absolute magnitude Mv, the surface gravity g, the Roche lobe filling fraction ?, and the Alfven radius RA are likely to be due to correlations of these quantities with the stellar radius R. Surprisingly, no correlation of Lx on the color (B-V), the rotation velocity Vrot, and the Rossby number RO is observed. However, significant correlations were found between the mean surface x-ray flux Fx = Lx/R2c + R2h with the orbital period Porb, the rotation velocity Vrot, the Rossby number RO. The activity-radius (and radius dependent parameters: ?, M, g, MV,and RA) correlations are mostly disappear when the mean surface flux Fx is used as the activity measure. We think the radius R (infact the surface area 4?R2) in Lx - R correlation represents the filling area S of the active regions on the stellar surface. The Lx thus increases with increasing surface area 4?R2 (in fact with increasing S). Slightly decreasing trend of the surface flux with the evolution off the main sequence (age or R2) can be understood in terms of the decreasing filling fraction (S/4?R2) of the active regions with age.