The X-ray Emission Reveals the Coronal Activities of Semi-detached Binaries

X-ray emission is an important tracer of stellar magnetic activity. We carried out a systematic correlation analysis for the X-ray luminosity $\log L_{\mathrm{X}}$, bolometric luminosity $\log L_{\mathrm{b}\mathrm{o}\mathrm{l}}$, and X-ray activity level $\log (L_{\text{X}}$/$L_{\text{bol}})$ versus the binary parameters including orbital period $P$, Rossby number $R_{\mathrm{O}}$, effective temperature $T_{\mathrm{e}\mathrm{f}\mathrm{f}}$, 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 $\log L_{\mathrm{X}}$ and $\log L_{\mathrm{b}\mathrm{o}\mathrm{l}}$ change in accordance with $\log P$ indicates that X-ray emission originates from the convection zone, while $\log L_{\mathrm{X}}$ 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 $\log T_{\mathrm{e}\mathrm{f}\mathrm{f}}$-$\log L_{\text{X}}$ and $M$-$\log L_{\text{X}}$ 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 $\log T_{\mathrm{e}\mathrm{f}\mathrm{f}}$ 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 $R_{\mathrm{O}}$-$\log (L_{\text{X}}\mathrm{/}{L}_{\text{bol}})$ 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 $\log L_{\mathrm{X}}$ and $\log (L_{\text{X}}$/$L_{\text{bol}})$.