** Authors:**
OSMAN DEMİRCAN, HASAN AK

** Abstract: **
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 L_x and the stellar radius R, the Roche lobe filling
fraction \Gamma, and the Alfven radius RA. The correlations of L_x
with the mass M, the absolute magnitude M_V, the surface gravity g,
the Roche lobe filling fraction \Gamma, and the Alfven radius RA are
likely to be due to correlations of these quantities with the stellar
radius R. Surprisingly, no correlation of L_x on the color (B-V), the
rotation velocity V_{rot}, and the Rossby number RO is observed.
However, significant correlations were found between the mean surface
x-ray flux F_x=L_x/R_c^2+R_h^2 with the orbital period P_{orb}, the
rotation velocity V_{rot}, the Rossby number RO. The activity-radius
(and radius dependent parameters: \Gamma, M, g, M_V, and RA)
correlations are mostly disappear when the mean surface flux F_x is
used as the activity measure. We think the radius R (infact the
surface area 4 \pi R^2) in L_x-R correlation represents the filling
area S of the active regions on the stellar surface. The L_x thus
increases with increasing surface area 4 \pi R^2 (in fact with
increasing S). Slightly decreasing trend of the surface flux with the
evolution off the main sequence (age or R^2) can be understood in
terms of the decreasing filling fraction (S/4 \pi R^2) of the active
regions with age.

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