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_ X, bolometric luminosity log L_ bol, and X-ray activity level log(L_X/L_bol) versus the binary parameters including orbital period P, Rossby number R_ O, effective temperature T_ 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_ X and log L_ bol change in accordance with log P indicates that X-ray emission originates from the convection zone, while log L_ 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_ eff-log L_X and M-log L_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_ 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_ O-log(L_X/L_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_ X and log(L_X/L_bol).