Temperature mass, and luminosity of RR Lyrae stars as functions of metallicity at the blue fundamental edge. II

The observed Oosterhoff period-metallicity effect of d log P/d([Fe/H]) = − 0.122 at the blue fundamental edge (BFE) of the instability strip can be reconciled with predictions from the canonical HB models if the observed period shift is not only a luminosity shift but a temperature shift as well. If so, predictions from models should not be made at constant temperature but at a temperature that varies with [Fe/H]. The sense is that low metallicity RR Lyraes have lower temperatures than those of higher metallicity by Δ log T e = 0.012 ± 0.006 per dex in [Fe/H], determined from observations of field RR Lyraes