Extended Aperture Photometry of K2 RR Lyrae stars

Abstract

The \textit{Kepler} space telescope observed thousands of RR Lyrae stars in the K2 mission. In this paper we present our photometric solutions using extended apertures in order to conserve the flux of the stars to the highest possible extent. With this method we are able to avoid most of the problems that RR Lyrae light curves produced by other pipelines suffer from. For post-processing we apply the K2SC pipeline to our light curves. We provide the EAP (Extended Aperture Photometry) of 432 RR Lyrae stars observed in campaigns 3, 4, 5, and 6. We also provide subclass classifications based on Fourier parameters. We investigated in particular the presence of the Blazhko effect in the stars, and found it to be 44.7\% among the RRab stars, in agreement with results from independent samples. We found that the amplitude and phase modulation in the Blazhko stars may behave rather differently, at least over the length of a K2 Campaign. We also identified four anomalous Cepheid candidates in the sample one of which is potentially the first Blazhko-modulated member of its class.

arXiv comment20 pages, 13 figures, accepted in ApJS, light curves available at https://konkoly.hu/KIK/data_en.html

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• Blazhko effect in the Galactic bulge fundamental mode RR Lyrae stars II: Modulation shapes, amplitudes and periods
• Studies of RR Lyrae Variables in Binary Systems. I.: Evidence of a Trimodal Companion Mass Distribution
• Asteroseismology of RR Lyrae stars with non-radial modes
• Frequency analysis of the first-overtone RR Lyrae stars based on the Extended Aperture Photometry from the K2 data
• Automated Extended Aperture Photometry of K2 variable stars
• Time series analysis of bright TESS RRc stars: Additional modes, phase variations and more
• Four 'Peculiar' RRd Stars Observed by K2
• 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
• Digging Deeper for RR Lyrae Stars with Low Modulation Amplitudes
• Matching seismic masses for RR Lyrae-type and oscillating red horizontal-branch stars in M4
• Periodic Variable Stars Modulated by Time-Varying Parameters
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