Date of Graduation

Spring 2018

Degree

Master of Natural and Applied Science in Physics

Department

Physics, Astronomy, and Materials Science

Committee Chair

Michael Reed

Keywords

subdwarf stars, oscillations, asteroseismology, Kepler, open cluster

Subject Categories

Astrophysics and Astronomy

Abstract

Using their entire Kepler data sets, I performed asteroseismic analyses and comparisons of three gravity (g-) mode pulsating subdwarf B (sdB) stars in the open cluster NGC 6791. I constructed light curves with a combination of long and short cadence data to span quarters 1 (Q01) through Q17 of KIC 2569576 (B3), KIC 2438324 (B4), and KIC 2437937 (B5). Rotationally induced g-mode frequency splittings were observed in each star allowing us to calculate rotation periods of 64.5 ± 8.2, 9.21 ± 0.18, and 91.3 ± 14.1 days for B3, B4, and B5, respectively. Using the observed ratio of the azimuthal multiplet components, I also constrained the inclination of the pulsation axis of each star and found that while B4 (76° < i < 84°) has an inclination close to equator-on, B3 (i < 62°) and B5 (8° < i < 30°) have inclinations which overlap with the preferred inclination of the cluster (20° < i < 30°). Asymptotic period spacings were determined in each star, and mode trapping was observed in one region of B3's asymptotic l = 1 sequence. From the full data sets of all three sdB stars, I detected a combined total of 65 pulsation frequencies of which I was able to identify 88% as l ≤ 2 modes. Using these results and the cluster characteristics which include a common age, progenitor mass, and preferred inclinations for the sdB stars in NGC 6791, I discuss the comparison of B3, B4, and B5 to the known population of

Copyright

© Joshua William Kern

Open Access

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