  The pulsational method to estimate the absolute magnitudes of RR Lyrae stars
is updated with new data on field-star metallicities by Layden, a new
calibration of the (B-V)_0-temperature correlation from recent atmospheric
models by Bell and Tripicco, and new mass estimates by Bono et al. New linear
and non-linear calibrations of M_V(RR)=f([Fe/H]) are derived that depend on the
nature of the adopted envelope in a diagram of log period versus metallicity
fitted to the shortest period field variables in each metallicity range,
together with the stated assumptions on the colour of the stars at that
envelope. These new cali- brations are compared with a recent non-linear
calibration by Caputo et al. The theoretical luminosity zero points for each of
the three new calibrations derived here agree with each other to within 0.1 mag
over the metallicity range of -1.0>[Fe/H]>-2.0. Comparison with the empirical
absolute magnitude calibra- tion of M_V(RR)=+0.52 at [Fe/H]=-1.5 by Clementini
at al. from RR Lyraes in LMC also shows agreement at the 0.05 mag level at the
stated metallicity. Our final compromise pulsational calibration is,
M_V(RR)=0.82 + 0.20([Fe/H]) with the caveat that the true relation is likely to
be non-linear at the 0.1 mag level for [Fe/H] values between -0.5 and -2.0,
hence with variable dM_V/d([Fe/H]) slopes that cover the range from 0 to 0.6
for different metallicities. (...)
