The Baade-Wesselink method and the distances to RR Lyrae Stars. VIII - Comparisons with other techniques and implications for globular cluster distances and ages

All techniques that derive M(V) or M(bol) as a function of Fe/H for RR Lyrae variables are summarized. Recent results from main-sequence fitting are revised to account for metallicity-dependent errors in B - V from model isochrones; M(V)(RR) is found to vary as 0.12(Fe/H). The equilibrium temperature scale is redefined for RR Lyrae stars, and the period-shift analyses for RR Lyrae stars in globular clusters and in the field are readdressed. All methods agree that, within the errors, M(V)(RR) varies as 0.15(Fe/H) and M(bol)(RR) varies as 0.19(Fe/H). If O/Fe = 0.3, the Galaxy's age may be as high as 20 +/-3 Gyr, and the most metal-poor clusters are on average older than the more metal-rich ones. If O/Fe varies as -0.4(Fe/H), the Galaxy's age is about 14 +/-2 Gyr, and the cluster's ages do not correlate with metallicity. Regardless of the oxygen abundance, there is a significant range in ages among the intermediate-metallicity clusters.