Involved people at OAB: Bragaglia, Clementini, Di Fabrizio.
The luminosity, the luminosity-metallicity and mass-metallicity
dependence for RR Lyrae variables in the bar of the Large
Magellanic Cloud and their role in measuring distances to the LMC
are being investigated, in collaboration with Carretta and Gratton (OAPD),
Maceroni (OAR), Marconi (OAN) and Castelli (CNR-TS).
B and V light curves have been obtained for 128 RR Lyraes
and low resolution spectra at minimum light have been obtained for
7 double-mode pulsators in the sample.
metal abundance have been estimated for the 7 RRd's. The average
metallicity of the sample is 
dex and the
mass metallicity relation they define closely resembles the one followed
by the Galactic globular clusters double mode pulsators, thus
leaving no room for significant differences in mass between field
and cluster variables (Bragaglia et al. 2000, AJ, submitted).
The global pulsational properties of the sample as well as a very accurate
estimate of the average apparent luminosity
of the LMC variables has been obtained from the photometric data :
mag. This value is in very good agreement with the
average luminosity of the LMC globular cluster RR Lyraes.
An independent estimate of the LMC reddening was obtained from the
colors of the edges of instability strip defined by the
RR Lyrae in our sample 
mag. This value is in perfect
agreement with reddening estimates obtained by Cepheids in the same region.
These new average apparent luminosity and reddening values
allow us to reconcile the short and long distance moduli of the
LMC on a common value of 
[Clementini et al. (2000, AJ,
submitted); Carretta et al. (2000, ApJ, 533, 215); Di Fabrizio et al.
(2000, A&A, submitted)].
We have just applied for observing time to measure the metallicities of
the entire sample of detected RR Lyraes using the method. This will
allow us to directly determine the slope of the luminosity-metallicity
relation for RR Lyrae stars.