Comparison of the observed Fe He|$\alpha$|-|$z/$|He|$\alpha$|-w and Ly|$\alpha$||$/$|He|$\alpha$|-w intensity ratios and AtomDB plasma models. The observed intensity ratios and their |$1\sigma$| uncertainty ranges are indicated with red transparent regions in the panels (a) and (b). (a) Comparison with the CIE model with various electron temperatures (⁠|$kT_{\rm e}$|⁠). The upper and lower panels show the He|$\alpha$|-|$z/$|He|$\alpha$|-w intensity ratio and ion fractions, respectively. (b) Comparison with the overionized plasma model (rnei with |$kT_{\rm e} = 1.6\:$|keV) with various initial temperatures (⁠|$kT_{\rm init}$|⁠). The upper and lower panels show the He|$\alpha$|-|$z/$|He|$\alpha$|-w and Ly|$\alpha$||$/$|He|$\alpha$|-w ratios as a function of recombination timescale, respectively. (c) |$1\sigma$| uncertainty ranges of |$kT_{\rm e}$| and present ionization temperature which satisfy the observed He|$\alpha$|-|$z/$|He|$\alpha$|-w (red) and Ly|$\alpha$||$/$|He|$\alpha$|-w (blue) ratios. (d) |$1\sigma$| confidence region of the recombination timescale and initial ionization temperature (⁠|$kT_{\rm init}$|⁠) (red) which satisfy both the observed He|$\alpha$|-|$z/$|He|$\alpha$|-w and Ly|$\alpha$||$/$|He|$\alpha$|-w ratios. The background color scale in panels (c) and (d) shows the He|$\alpha$|-|$z/$|He|$\alpha$|-w intensity ratio.