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Analysis of a subdwarf B pulsator observed during Campaign 2 of K2
Laura Ketzer (Missouri State University), A.S. Baran (Krakow Pedagogical University), M.D. Reed (Missouri State University), J.H. Telting (Nordic Opitical Telescope), P. Nemeth (KU Leuven)
We present an analysis of the pulsating subdwarf B (sdB) star EPIC 203948264, observed during Campaign 2 of the extended Kepler mission. A time series analysis of the short cadence data set has revealed a rich g-mode pulsation spectrum with 16 independent pulsation periods between 0.5 and 2.8 hours. Most of the pulsations fit the asymptotic period sequences for ell=1 or 2, with average period spacings of 261.34+/-0.78 and 151.18+/-0.34 s, respectively. The pulsation amplitudes are below 0.77 ppt and vary over time. Radial velocity measurements give no indication for binarity in this star. We did not find rotationally induced pulsation multiplets, which indicates that the rotation period of the star is longer than about 45 days, which would make the data too short to resolve multiplets. By characterizing the various pulsation modes present in pulsating sdB stars, and by examining the time-dependence of pulsation amplitudes, we can constrain structural models of the interiors of sdB stars. This is a promising approach to enhancing our understanding of blue horizontal branch stars.