Student: Paige Leeseberg, Undergraduate Student in Physics, Iowa State University
Research Mentor: Dr. Massimo Marengo
The Calibration of the Period-Luminosity Relation of RR Lyrae in Globular Clusters
I have been working under Professor Marengo with his research on star clusters since the fall of 2019 at Iowa State University. This project consists of processing and analyzing images of globular clusters in the Galactic halo and the Large Magellanic Cloud taken by the NASA Spitzer Space Telescope. The goal of the project is to use variable stars in these clusters as “yardsticks” to measure the Hubble Constant, which describes the rate of expansion of the universe. The specific stars that we are looking for are RR Lyrae. We can use RR Lyrae as yardsticks because of the period-luminosity relation for stars in the infrared. Each cluster has been observed for a minimum of 12 epochs, and this allows us to measure the brightness variation of the variables. When making the mosaics I use a program called MOPEX which splices together the individual image from each epoch to get a single image. With 47 clusters to analyze with at least 10 images apiece (5 dithers for 2 for two fields of view), this takes time and patience. The next step in this project is to measure the light curve of the stars in these clusters to identify the RR Lyrae stars. For this part of the project, I am using a program called DAOPHOT which specifically measures photometry. All the analysis that I am doing is through Python.