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Variable stars change in brightness over regular or semiregular periods of time. Causes of variability include pulsation (changes in size) or the presence of a companion star or planet that eclipses part of the stellar surface. We examine period changes of the bright variable stars Alpha Orionis (Betelgeuse) and Beta Lyrae using data from the American Association of Variable Star Observers (AAVSO). Periods were analyzed by applying Fourier and weighted wavelet z-transforms to the light curves of each star over a 30-year time span. Our analyses showed that both the short and long secondary periods of Betelgeuse changed with time. The long period decreased at a nearly constant rate, and the short period increased in sudden “jumps” before suddenly decreasing. The period of Beta Lyrae had only small variations surrounding the expected period, with the exception of a sudden 3-day decrease which immediately increased back to the expected period again. The AAVSO database contains contributions from amateur and student observers: our ultimate goal is to use an older DSLR to contribute to the AAVSO database of bright variable stars.

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Period Analyses of Variable Stars Alpha Orionis and Beta Lyrae



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