On the modulation of RR Lyrae stars in the globular cluster M3

Abstract

A new, extended time-series photometry of M3 RR Lyrae stars has revealed that four of the ten double-mode stars show large-amplitude Blazhko modulation of both radial modes. The first, detailed analysis of the peculiar behavior of the unique, Blazhko RRd stars is given. While the P1/P0 period ratio is normal, and the overtone mode is dominant in the other RRd stars of the cluster, the period ratio is anomalous and the fundamental mode has a larger (or similar) mean amplitude than the overtone has in Blazhko RRd stars. The modulations of the fundamental and overtone modes are synchronized only in one of the Blazhko RRd stars. No evidence of any connection between the modulations of the modes in the other three stars is found. The Blazhko modulation accounts, at least partly, for the previously reported amplitude and period changes of these stars. Contrary to the $\sim 50$ Blazhko statistics of RRab and RRd stars, Blazhko modulation occurs only in 10 of the overtone variables in M3. Four of the five Blazhko RRc stars are bright, evolved objects, and one has a similar period and brightness as Blazhko RRd stars have. The regions of the instability strip with high and low occurrence rate of the Blazhko modulation overlap with the regions populated by first- and second-generation stars according to theoretical and observational studies, raising up the possibility that the Blazhko modulation occurs preferentially in first-generation RR Lyrae stars.

6 pages, 4 figures, accepted for publication in ApJL

References in corpus (8)

• The fraction of second generation stars in Globular Clusters from the analysis of the Horizontal Branch
• Optical and Near-Infrared UBVRIJHK Photometry for the RR Lyrae stars in the Nearby Globular Cluster M4 (NGC 6121)
• Frequency analysis of Cepheids in the Large Magellanic Cloud. New types of classical Cepheid pulsators
• Long time-scale behavior of the Blazhko effect from rectified Kepler data
• MOST photometry of the RRd Lyrae variable AQ Leo: Two radial modes, 32 combination frequencies, and beyond
• Constraints on Helium Enhancement in the Globular Cluster M3 (NGC 5272): The Horizontal Branch Test
• Multicolour CCD photometry of the variable stars in globular cluster M3
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• Discovery of a new group of double-periodic RR Lyrae stars in the OGLE-IV photometry
• Peculiar double-periodic pulsation in RR Lyrae stars of the OGLE collection. I. Long-period stars with dominant radial fundamental mode
• Peculiar double-periodic pulsation in RR Lyrae stars of the OGLE collection. II. Short-period stars with dominant radial fundamental mode
• Revisiting the Kepler non-Blazhko RR Lyrae sample: Cycle-to-cyle variations and additional modes
• A double-modulation effect detected in a double-mode high-amplitude $\delta$ Scuti star: KIC 10284901
• Frequency analysis of the first-overtone RR Lyrae stars based on the Extended Aperture Photometry from the K2 data
• The SuperWASP catalogue of 4963 RR Lyr stars: identification of 983 Blazhko effect candidates
• The SERMON project: 48 new field Blazhko stars and an investigation of modulation-period distribution
• First Overtone Cepheids of the OGLE Magellanic Cloud Collection -- beyond radial modes
• Possible evidence of hydrogen emission in the first-overtone and multi-mode RR Lyrae variables
• Two Different Weak Modulations in ab-type RR Lyrae Variable V838 Cyg, and Potential Influence of Metal Abundance on Blazhko Modulation
• On the incidence rate of RR Lyrae stars with non-radial modes
• Caught in the Act: Observations of the Double-mode RR Lyrae V338 Boo During the Disappearance of a Pulsation Mode