Determinations of temperature and density for solar-like Stars using Si   XI soft X-ray emission lines
  We study temperature and density sensitivities of ratios of Si XI soft X-ray emission lines, in the wavelength range of 43--54\AA . The typical temperature of the formation of the analyzed lines is around 1.6~MK, which makes this analysis complementary to the analysis of He-like triplets being sensitive to hotter plasma. We present theoretical calculations and compare them with ratios obtained from high-resolution X-ray spectra of five solar-like stars: Procyon, $\alpha$ Cen A$&$B, $\epsilon$ Eri, and Capella. We find that our results are in good agreement with results obtained by other authors through different diagnostics, namely the analysis of density- and temperature-sensitive He-like triplet lines. We further estimate the coronal pressure and filling factors from Si~XI lines in this study. 
G. Y. Liang, G. Zhao