Four 'Peculiar' RRd Stars Observed by K2

Abstract

Four stars pulsating simultaneously with a dominant period $P_D$$\in$(0.28,0.39) d and an {\it additional} period $P_A$$\in$(0.20,0.27) d have been identified from among the more than 3000 RR Lyrae stars observed by the Kepler space telescope during NASA's K2 Mission. All four stars are located in the direction of the Galactic Bulge and have period ratios, $P_A$/$P_D$, significantly smaller than those of most double-mode RR Lyrae (RRd) stars: $P_A$/$P_D$$\in$(0.694,0.710) vs. $P_1$/$P_0$$\in$(0.726,0.748). Three of the stars are faint ($<$$V$$>$=18--20 mag) and distant and are among the `peculiar' RRd (pRRd) stars discovered by Prudil et al. (2017); the fourth star, EPIC 216764000 (=V1125 Sgr), is a newly discovered pRRd star several magnitudes brighter than the other three stars. In this paper the high-precision long-cadence K2 photometry is analyzed in detail and used to study the cycle-to-cycle light variations. The pulsational characteristics of pRRd stars are compared with those of `classical' and `anomalous' RRd (cRRd, aRRd) stars. The conclusion by Prudil et al. that pRRd stars form a separate group of double-mode pulsators and are not simply very-short-period cRRd stars is confirmed. V1127 Aql and AH Cam are identified as other probable members of the class of pRRd stars.

arXiv comment23 pages, 16 figures

References in corpus (60)

• Gaia Data Release 2. Summary of the contents and survey properties
• The K2 Mission: Characterization and Early results
• The WASP Project and the SuperWASP Cameras
• Kepler Presearch Data Conditioning II - A Bayesian Approach to Systematic Error Correction
• The Pan-STARRS1 Surveys
• The first WASP public data release
• The K2 Ecliptic Plane Input Catalog (EPIC) and Stellar Classifications of 138,600 Targets in Campaigns 1-8
• EVEREST: Pixel Level Decorrelation of K2 Light curves
• SigSpec - I. Frequency- and Phase-Resolved Significance in Fourier Space
• Metal Abundances, Radial Velocities and other Physical Characteristics for the RR Lyrae Stars in the Kepler Field
• The MACHO Project LMC Variable Star Inventory. IX. Frequency Analysis of the First Overtone RR Lyrae Stars and the Indication for Nonradial Pulsations
• The Konkoly Blazhko Survey: Is light-curve modulation a common property of RRab stars?
• Flavours of variability: 29 RR Lyrae stars observed with Kepler
• Analysis of RR Lyrae Stars in the Northern Sky Variability Survey
• K2P${}^2$ $-$ A photometry pipeline for the K2 mission
• The ACS LCID Project. I. Short-Period Variables in the Isolated Dwarf Spheroidal Galaxies Cetus & Tucana
• Fourier analysis of non-Blazhko ab-type RR Lyrae stars observed with the Kepler space telescope
• Nonlinear Beat Cepheid and RR Lyrae Models
• Kepler photometry of RRc stars: peculiar double-mode pulsations and period doubling
• The MACHO Project LMC Variable Star Inventory IV: Multimode RR Lyrae Stars, Distance to the LMC and Age of the Oldest Stars
• Spectroscopic Comparison of Metal-Rich RRab Stars of the Galactic Field with Their Metal-Poor Counterparts
• 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
• Stellar evolution through the ages: period variations in galactic RRab stars as derived from the GEOS database and TAROT telescopes
• MOST photometry of the RRd Lyrae variable AQ Leo: Two radial modes, 32 combination frequencies, and beyond
• Multiperiodic Galactic field RR Lyrae stars in the ASAS catalog
• The Metallicity Dependence of the Fourier Components of RR Lyrae Light Curves is the Oosterhoff/Arp/Preston Period Ratio Effect in Disguise
• RR Lyrae stars in the Sagittarius dwarf galaxy: Period analysis
• Automated Nonlinear Stellar Pulsation Calculations: Applications to RR Lyrae stars. The Slope of the Fundamental Blue Edge and the First RRd Model Survey
• Revisiting CoRoT RR Lyrae stars: detection of period doubling and temporal variation of additional frequencies
• Overtone and multi-mode RR Lyrae stars in the globular cluster M3
• Image-Subtraction Photometry of the Globular Cluster M3: identification of new double-mode RR Lyrae stars
• Anomalous Double-Mode RR Lyrae Stars in the Magellanic Clouds
• An RR Lyrae family portrait: 33 stars observed in Pisces with K2-E2
• Blazhko-type modulation in the double-mode RR Lyrae stars of the OGLE Galactic bulge collection
• Double-mode radial-non-radial RR Lyrae stars in the OGLE photometry of the Galactic bulge
• The OGLE Collection of Variable Stars. Classical, Type II, and Anomalous Cepheids toward the Galactic Center
• On the double-mode RR Lyrae variables of the Sculptor dwarf galaxy
• Photometric and radial-velocity time-series of RR Lyrae stars in M3: analysis of single-mode variables
• Double-mode radial-non-radial RR Lyrae stars. OGLE-IV photometry of two high cadence fields in the Galactic bulge
• A Mid-infrared Study of RR Lyrae Stars with the WISE All-Sky Data Release
• Blazhko modulation in the infrared
• The census of non-radial pulsation in first-overtone RR Lyrae stars of the OGLE Galactic bulge collection
• Peculiar double-periodic pulsation in RR Lyrae stars of the OGLE collection. I. Long-period stars with dominant radial fundamental mode
• The all-sky GEOS RR Lyr survey with the TAROT telescopes. Analysis of the Blazhko effect
• Peculiar double-periodic pulsation in RR Lyrae stars of the OGLE collection. II. Short-period stars with dominant radial fundamental mode
• EPIC 201585823, a rare triple-mode RR Lyrae star discovered in K2 mission data
• The chemical composition of the Small Magellanic Cloud
• Extended Aperture Photometry of K2 RR Lyrae stars
• Are all RR Lyrae stars modulated?
• Blazhko Effect in the first overtone RR Lyrae stars of the OGLE Galactic bulge collection
• Evolution of Horizontal Branch Stars in Globular Clusters: The Interesting Case of V79 in M3
• Metal-Rich RRc stars in the Carnegie RR Lyrae Survey
• RR Lyrae stars in NGC 6362
• Over 78 000 RR Lyrae Stars in the Galactic Bulge and Disk from the OGLE Survey
• The SuperWASP catalogue of 4963 RR Lyr stars: identification of 983 Blazhko effect candidates
• Multi-Mode Oscillations in Classical Cepheids and RR Lyrae-Type Stars
• Concluding Henrietta Leavitt's Work on Classical Cepheids in the Magellanic System and Other Updates of the OGLE Collection of Variable Stars
• K2P${}^2$: Reduced data from campaigns 0-4 of the K2 mission
• On the Cepheid Metallicity Dichotomy

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