Normalized distributions of three spectral parameters (log T_eff, [Fe/H], and log g) of EWXs, and their relationships with log L_X and log(L_X/L_bol). Upper panels: normalized distributions of the binary temperature (1–1), metallicity [Fe/H] (2–1), and surface gravity log g (3–1). The red and black broken lines represent the EW-type binaries collected by Qian et al. (2017) and our Spec-EWX sample, respectively. Middle panels: relationships between log L_X and the binary temperature (1–2), metallicity [Fe/H] (2–2), and surface gravity log g (3–2). Lower panels: relationships between log(L_X/L_bol) and the binary temperature (1–3), metallicity [Fe/H] (2–3), and surface gravity log g (3–3). Solid black lines are the least-squares linear fits and the light black dashed lines represent the 95% uncertainty ranges.