A Double‐Mode RR Lyrae Star with a Strong Fundamental‐Mode Component

NSVS 5222076, a 13th magnitude star in the Northern Sky Variability Survey, was identified by L. Oaster as a possible new double‐mode RR Lyrae star. We confirm the double‐mode nature of NSVS 5222076, supplementing the survey data with new V‐band photometry. NSVS 5222076 has a fundamental‐mode period (P0) of 0.4940 days and a first‐overtone period (P1) of about 0.3668 days, giving a period ratio of P1/P0 = 0.743. In most double‐mode RR Lyrae stars, the amplitude of the first‐overtone mode's pulsation is greater than that of the fundamental‐mode pulsation. That is not true for this star. Its fundamental‐mode light curve has an amplitude twice as large as that of the first‐overtone mode, a ratio very rarely seen even among the double‐mode RR Lyrae stars that have relatively strong fundamental‐mode pulsation. Data from the literature are used to discuss the location in the Petersen diagram of double‐mode RR Lyrae stars having strong fundamental‐mode pulsation. Such stars tend to occur toward the short‐period end of the Petersen diagram, and NSVS 5222076 is no exception to this rule.