A double-mode RR Lyrae star with a strong fundamental-mode component.
OASTER L., SMITH H.A. and KINEMUCHI K.
Abstract (from CDS):
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.