Two Different Weak Modulations in ab-type RR Lyrae Variable V838 Cyg, and Potential Influence of Metal Abundance on Blazhko Modulation

Abstract

Noting the weakest modulation and relatively high metal abundance of the ab-type RR Lyrae star V838 Cyg, we collected the photometric data of this star from several sky surveys to carry out an in-depth analysis. The O-C diagram shows that the pulsation period of V838 Cyg increases linearly over a long timescale. In a reanalysis of the high-precision Kepler data, we confirmed the modulation with a period of 59.45\pm0.07 days found by Benko et al., (2014), and also found an additional weak modulation with a longer period (840\pm21 days). After a series of analyses, we incline to the view that the mechanisms causing the two modulations are different: the former is more similar to the typical Blazhko effect, while the mechanism leading to the latter may be an extrinsic factor. We also collected and compared the modulation and physical parameters of other Blazhko RR Lyrae stars from several works in the literature, and find that there is a potential negative correlation between the modulation amplitude (or upper limit of amplitude) and the metal abundance. We infer that the relatively high metal abundance will promote convection in the outer stellar atmosphere, and then inhibit those factors (turbulence, shock wave, etc.) that may cause Blazhko modulation. Future observations and research work can be carried out with reference to this viewpoint. We also introduce the moire effects that appear in the Kepler long-cadence light curves and their possible interference in the previous analyses.

arXiv comment22 pages, 12 figures

References in corpus (49)

• The Transiting Exoplanet Survey Satellite
• The Man Behind the Curtain: X-rays Drive the UV through NIR Variability in the 2013 AGN Outburst in NGC 2617
• Kepler Mission Design, Realized Photometric Performance, and Early Science
• Achieving better than 1 minute accuracy in the Heliocentric and Barycentric Julian Dates
• Rotation Periods of 34,030 Kepler Main-Sequence Stars: The Full Autocorrelation Sample
• The ASAS-SN Catalog of Variable Stars I: The Serendipitous Survey
• The first WASP public data release
• Triple-Star Candidates Among the Kepler Binaries
• Metal Abundances, Radial Velocities and other Physical Characteristics for the RR Lyrae Stars in the Kepler Field
• FM stars: A Fourier view of pulsating binary stars, a new technique for measuring radial velocities photometrically
• Does Kepler unveil the mystery of the Blazhko effect? First detection of period doubling in Kepler Blazhko RR Lyrae stars
• First Kepler results on RR Lyrae stars
• The Konkoly Blazhko Survey: Is light-curve modulation a common property of RRab stars?
• Flavours of variability: 29 RR Lyrae stars observed with Kepler
• The Anticorrelated Nature of the Primary and Secondary Eclipse Timing Variations for the Kepler Contact Binaries
• On the Blazhko Effect in RR Lyrae Stars
• Short period eclipsing binary candidates identified using SuperWASP
• Fourier analysis of non-Blazhko ab-type RR Lyrae stars observed with the Kepler space telescope
• Period doubling bifurcation and high-order resonances in RR Lyrae hydrodynamical models
• Spectroscopic Comparison of Metal-Rich RRab Stars of the Galactic Field with Their Metal-Poor Counterparts
• Stellar evolution through the ages: period variations in galactic RRab stars as derived from the GEOS database and TAROT telescopes
• Long time-scale behavior of the Blazhko effect from rectified Kepler data
• SuperWASP observations of pulsating Am stars
• Blazhko RR Lyrae light curves as modulated signals
• Period and light curve fluctuations of the Kepler Cepheid V1154 Cyg
• On the use of field RR Lyrae as Galactic probes: I. The Oosterhoff dichotomy based on fundamental variables
• RR Lyrae stars in Galactic globular clusters. VI. The Period-Amplitude relation
• Asteroseismology of KIC 11754974: a high-amplitude SX Phe pulsator in a 343-day binary system
• Variability of M giant stars based on Kepler photometry: general characteristics
• The Kepler Cepheid V1154 Cyg revisited: light curve modulation and detection of granulation
• Metallicity of Galactic RR Lyrae from Optical and Infrared Light Curves: I. Period-Fourier-Metallicity Relations for Fundamental Mode RR Lyrae
• Probing the galactic halo with RR Lyrae stars I: The catalog
• Long-term variability of T Tauri stars using WASP
• Cyclic variations in O-C diagrams of field RR Lyrae stars as a result of LiTE
• Blazhko effect in the Galactic bulge fundamental mode RR~Lyrae stars I: Incidence rate and differences between modulated and non-modulated stars
• On the use of field RR Lyrae as Galactic probes: IV. New insights into and around the Oosterhoff dichotomy
• Multiple Populations in Globular Clusters and the Origin of the Oosterhoff Period Groups
• Bright Blazhko RRab Lyrae stars observed by ASAS and the SuperWASP surveys
• On the modulation of RR Lyrae stars in the globular cluster M3
• Blazhko effect in the Galactic bulge fundamental mode RR Lyrae stars II: Modulation shapes, amplitudes and periods
• The all-sky GEOS RR Lyr survey with the TAROT telescopes. Analysis of the Blazhko effect
• Magnetic, chemically peculiar (CP2) stars in the SuperWASP survey
• Metallicity of Galactic RR Lyrae from Optical and Infrared Light Curves: II. Period-Fourier-Metallicity Relations for First Overtone RR Lyrae
• Are all RR Lyrae stars modulated?
• Revisiting the Kepler non-Blazhko RR Lyrae sample: Cycle-to-cyle variations and additional modes
• The Blazhko effect and additional excited modes in RR Lyrae stars
• Amplitude Fine-Structure in the Cepheid P-L Relation I: Amplitude Distribution Across the RR Lyrae Instability Strip Mapped Using the Accessibility Restriction Imposed by the Horizontal Branch
• Reanalysis of c-type RR Lyrae Variable BE Dor, Period Modulations and Possible Mechanism
• Is the Blazhko effect the beating of a near-resonant double-mode pulsation?

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