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RR Lyrae Stars in the Globular Cluster M4
Charles Kuehn (University of Northern Colorado), Pawel Moskalik (Copernicus Astronomical Center), Jason Drury (University of Sydney)
Observations by Kepler/K2 have revolutionized the study of RR Lyrae stars by allowing DETECTION OF phenomena, such as additional modes and period doubling, which had not previously been seen from the ground. During campaign 2, K2 observed the globular cluster M4, providing the first opportunity to study a SIZEABLE group of RR Lyrae that belong to a single population; the other RR Lyrae that have been observed from space are field stars in the galactic halo and thus belong to an assortment of populations. In this poster we present the results from our study of the RR Lyrae in M4 from K2 photometry. We have identified additional, low amplitude pulsation modes in both observed RRc stars. In 3 RRab stars we have found the Blazhko effect with periods of 16.6 days, 22.4 days and 44.5 days.