Color Photometry and Pulsation Periods of RR Lyrae Stars in the Globular Cluster NGC 3201
Volume 52 number 2 (2024)
- Maiya Qiu
- Stanford Online High School, Redwood City, CA 94063; maiyaq6487@gmail.com
- Nicholas Peh
- Stanford Online High School, Redwood City, CA 94063; nicholaspeh27@yahoo.com
- Eden (Songxiao) Li
- Stanford Online High School, Redwood City, CA 94063; lisongxiao7@gmail.com
- Kalée Tock
- Stanford Online High School, Redwood City, CA 94063; kaleeg@stanford.edu
Abstract
We selected the RR Lyrae stars V6, V26, V51, and V66 in the globular cluster NGC 3201 for analysis in B, V, SR, and SI filters. These four stars are Blažko candidates due to their modulating period or amplitude. We found possible Blažko candidacy for V66 by comparing past literature and archival data with our images, finding the best period changing from 0.6675 d in 2021 to 0.6667 d in 2024. V6, V26, and V51 do not appear to have clearly modulating periods between studies from 2021 and 2024; however, for these stars, we present an update to the Clement catalog periods which were taken from older observations. Light curves were fitted using point spread function photometry, which was found to produce significantly cleaner light curves compared to those created by source extractor photometry. We also present the amplitudes of the target stars and situate them in their stellar environments using a Color Magnitude Diagram (CMD) and Bailey diagram of the NGC 3201 cluster. Isochrone fits used the software Astromancer, whose metallicity output was converted from [M/H] to [Fe/H] for comparison with past literature. The resulting metallicity was lower than expected although the uncertainty range here does not necessitate a recategorization from the Oosterhoff dichotomy Type I to Type II.