We use theoretical models to establish a tight relationship for the absolute magnitudes of RR Lyrae stars as a function of their periods and Strömgren pseudo-color c _ { 0 } \equiv ( u - v ) _ { 0 } - ( v - b ) _ { 0 } .
Applying this to RR Lyr , and comparing the result with the predicted average absolute magnitude for stars of similar metallicity from the same models , yields an overluminosity of 0.064 \pm 0.013 mag in Strömgren y ( and thus similarly in V ) for RR Lyr .
Based on a revised value for RR Lyr ’ s trigonometric parallax , and on a newly derived reddening value of E ( \bv ) = 0.015 \pm 0.020 , we provide a corrected relationship between average absolute magnitude and metallicity for RR Lyrae stars that takes RR Lyr ’ s evolutionary status fully into account for the first time .
Applying this relationship to the LMC , we derive a revised true distance modulus of ( m - M ) _ { 0 } = 18.44 \pm 0.11 .