X-ray emission is an important tracer of stellar magnetic activity. We carried out a systematic correlation analysis for the X-ray luminosity $\log L_{ \rm X}$, bolometric luminosity $\log L_{ \rm bol}$, and X-ray activity level $\log(L_{ \textrm{ X}}$/$L_{ \textrm{ bol}})$ versus the binary parameters including orbital period $P$, Rossby number $R_{ \rm O}$, effective temperature $T_{ \rm eff}$, metallicity [Fe/H] and the surface gravity $\log g$, and the stellar mass $M$ \& radius $R$, by assembling a large sample of semi-detached (EB-type) binaries with X-ray emission (EBXs). The fact that both $\log L_{ \rm X}$ and $\log L_{ \rm bol}$ change in accordance with $\log P$ indicates that X-ray emission originates from the convection zone, while $\log L_{ \rm X}$ is proportional to the convection zone area. We found that EBXs with main-sequence components exhibit an upward and then a downward trend in both the $\log T_{ \rm eff}$-$\log L_{ \textrm{ X}}$ and $M$-$\log L_{ \textrm{ X}}$ relations, which is different from the monotonically decreasing trend shown by EBXs containing sub-giant and giant components. The magnetic activity level is negatively correlated with $\log T_{ \rm eff}$ and stellar mass. Based on the magnetic dynamo model, the variations in the size and thickness of the surface convection zones can explain the observed relations. EBXs with main-sequence components have similar $R_{ \rm O}$-$\log(L_{ \textrm{ X}}/L_{ \textrm{ bol}})$ relationship to that of the binaries in the clusters as Praesepe and Hyade. We compared the X-ray radiation properties of EBXs with those of the X-ray-emitting contact binaries and found that EBXs have broader value ranges for $\log L_{ \rm X}$ and $\log(L_{ \textrm{ X}}$/$L_{ \textrm{ bol}})$.
Categories: astro-ph.SR astro-ph.HE