DISTANCES AND LUMINOSITIES FOR RR LYRAE STARS IN M-5 AND M-92 FROM A BAADE-WESSELINK ANALYSIS

We present an improved fitting procedure for the surface-brightness va riant of the Baade-Wesselink method and absolute magnitudes and distan ces to two RR Lyrae stars in M 5 and two in M 92. The new statistical method has been developed to more objectively match the spectroscopic and photometric angular diameter variations, which is necessary to suc cessfully cope with the lower precision in the K band photometry for t he faint cluster variables vs. the bright field RR Lyraes previously s tudied. Within the uncertainties we do not detect a significant differ ence between the cluster and field RR Lyrae stars. The distances to M 5 and M 92 are estimated to be 14.(m)37 +/- 0.18 and 14.(m)60 +/- 0.26 respectively. Our results suggest that previous age estimates for M 9 2 and other metal-poor clusters may be too large although the current uncertainties prevents us from firmly establishing this.