First observations of W Virginis stars with K2: detection of period doubling

Abstract

We present the first analysis of W Vir stars observed by the Kepler space telescope in the K2 mission. Clear cycle-to-cycle variation were detected in the light curves of KT Sco and the globular cluster member M80-V1. While the variations in the former star seems to be irregular on the short time scale of the K2 data, the latter appears to experience period doubling in its pulsation. Ground-based colour data confirmed that both stars are W Vir-type pulsators, while a comparison with historical photometric time-series data revealed drastic period changes in both stars. For comparison we reexamine ground-based observations of W Vir, the prototype of the class, and conclude that it shows period doubling instead of mode beating. These results support the notion that nonlinear dynamics plays an important role in the pulsation of W Virginis-type stars.

8 pages, 7 figures, accepted for publication in MNRAS

References in corpus (8)

• The Dartmouth Stellar Evolution Database
• The K2 Mission: Characterization and Early results
• Achieving better than 1 minute accuracy in the Heliocentric and Barycentric Julian Dates
• The Catalina Surveys Periodic Variable Star Catalog
• The first WASP public data release
• The period-luminosity relation for type II Cepheids in globular clusters
• Multicolor photometry of the Type II Cepheid prototype W Virginis
• Intriguing triple-mode RR Lyrae star with period doubling

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• Zwicky Transient Facility and Globular Clusters: The Period-Luminosity and Period-Wesenheit Relations for Type II Cepheids
• An absolute calibration of the near-infrared Period-Luminosity Relations of Type II Cepheids in the Milky Way and in the Large Magellanic Cloud
• V473 Lyr, a modulated, period-doubled Cepheid, and U TrA, a double-mode Cepheid observed by MOST
• To Grow Old and Peculiar: A Survey of Anomalous Variable Stars in M80 and Age Determination using K2 and Gaia
• Type II and anomalous Cepheids in the Kepler K2 mission
• Connections between the cycle-to-cycle light curve and O-C variations of the non-Blazhko RR Lyrae stars