Pulsating Variable Stars

This REU summer project dealt mainly with analyzing data and determining the periods of certain types of pulsating variable stars called RR Lyraes and Cepheids. Pulsating variables periodically change in brightness over a certain amount of time for reasons having to do with the internal structure of the star itself. Dr. Horace Smith has been studying such variables in our neighboring galaxy, the Small Magellanic Cloud, for years. His studies have concentrated on surveying the different types of variables and determining periods for many fainter ones, which could be used by other studies to better determine the distance to the SMC, and thus to more distant galaxies. This study was able to contribute the discovery of one long period variable to his survey of a region of sky in the Northeast arm of the SMC. In addition to reducing some of the last data for Smith’s SMC survey, this project involved observing a variable RR Lyrae star, XZ Cygnae, with a relatively long period of about 57.3 days imposed upon a much shorter primary period. XZ Cygnae exhibits the Blazhko effect, which is responsible for causing this long period variation. Although the cause of the Blazhko effect is not understood at this point, a better determination of the current Blazhko period could help to test one of the theories. Sufficient data has not been collected as of the end of this summer to either support or contest this theory, but observations of XZ Cygnae will be continued into the fall, so that more data will be available.