Equivalent width of the He I λ10830 feature vs. the ratio of soft X-ray luminosity to bolometric luminosity for dwarf stars in the studies of Zarro & Zirin (1986) and Takeda & Takada-Hidai (2011). Stellar spectral class is denoted: F7-G8 (open circles), K (filled circles). Stars with [Fe/H]  < −0.4 are marked by open triangles. The metal-poor stars from the XMM-Newton program reported here are marked by a star symbol along with an arrow indicating an upper limit. The range of ﹩{L}_{{\rm{X}}}/{L}_{{\rm{bol}}}﹩ for the Sun in the ROSAT/PSPC band (Ayres 2014) is shown by the dashed line bounded by the letter S. The equivalent width at solar maximum and minimum is taken from the study of Livingston (1992), who finds a variation from ∼40 mÅ at solar minimum to ∼80 mÅ at solar maximum.