M5 RR Lyr and HB VI light curves

The results for RRab and RRc stars should be considered independent since they come from different calibrations and zero points. Absolute magnitudes, radii and masses are also reported for individual RR Lyrae stars. The distance to the cluster was also calculated by alternative methods like the Period-Luminosity relation of SX Phe and the luminosity of the stars at the tip of the red giant branch, and we obtained the results 7.7+/-0.4 and 7.2-7.5kpc respectively.

The distribution of RR Lyrae stars in the instability strip is discussed and compared with other clusters in connection with the Oosterhoff and horizontal branch type. The Oosterhoff type II clusters systematically show a RRab-RRc segregation about the instability strip first-overtone red edge, while the Oosterhoff type I clusters may or may not display this feature. A group of RR Lyrae stars is identified in an advanced evolutionary stage, and two of them are likely binaries with unseen companions.