A search for double-mode RR Lyrae stars in M3

Photometric observations obtained between 1895 and 1962 are used to systematically search for double mode RR Lyrae (RRd) stars in M3. Of the 46 stars considered, only V68 and V87 (both of which were previously identified as double-mode pulsators) are shown to be certain RRd variables. Masses of 0.52 + or - 0.005 solar masses for V68 and 0.55 + or - 0.015 solar masses for V87 are obtained, confirming the suggestion that RRd stars in Oosterhoff Type I systems are systematically 20 percent less massive, and correspondingly less luminous, than RRd stars in Oosterhoff Type II systems. Although evidence is found for cycle-to-cycle light variations, no significant long-term amplitude changes were noted.