Analysis and Fourier Decomposition of RR Lyrae Variables in the Globular Cluster IC4499

Indianapolis, IN

Using several hundred images collected with the Southeastern Association for Research in Astronomy (SARA) 0.6-meter telescope located at Cerro Tololo, Chile, we analyzed the variable stars of the globular star cluster IC4499. The images were examined using a method called difference image analysis (DIA). DIA compares each image to a reference image then produces a light curve of each variable star it finds. Given the crowded stellar fields found in globular clusters, DIA is by far the best method for producing high-quality light curves. Once produced the light curves were analyzed using Fourier decomposition. This method allowed us to determine the physical characteristics of the variable stars found within the cluster. These characteristics include the temperature, radius, stellar mass, and composition of the variable stars. In my talk I will present the results of this study. Understanding variable stars such as RR Lyrae stars provides astronomers with important tests of stellar evolution theory and for testing stellar pulsation theory. Thus, these variable stars provide information about each cluster that would otherwise not be directly accessible from studies of the non-variable cluster stars.