Identifying RR Lyrae variable stars in the NoirLab Source Catalog with template fitting

Abstract

RR Lyrae are periodic variable stars generally with periods between 5 hours and 1 day. They can be used as standard candles for accurate distance measurements and thus are useful for studying the structure of the Milky Way and its stellar clusters. The second data release of the NoirLab Source Catalog is a large collection of 68 billion time-series measurements of 3.9 billion objects. To process this large volume of data, we designed a computer software package in Python called Leavitt to automate the detection process and measure their properties including period, magnitude, epoch of maximum brightness and amplitude of their pulsations by fitting their light curves to templates. In addition to identifying RR Lyrae, it is expected that Leavitt can be extended to identify similar variable stars such as Cepheids in the same dataset. Distances were calculated for the initial catalog of RR Lyrae candidates using parameters measured with this script.