Thesis Committee: Henry Everitt, Steve Danford, John Kolena, Ronen Plesser, Calvin Howell (exofficio non-voting member)
ABSTRACT: Globular Cluster M14 is variable rich, with 93 previously identified variable stars, including 5 known Population II Cepheids, 54 RR Lyrae, and 6 red irregular variables (Clement 2001, Wehlau 1994). Periods have been found for 61 of these 90 variables using photographic photometry derived from plates and techniques outlined in Wehlau & Froelich (1994), where magnitude measurements were obtained via iris photometry and eye estimates, and periods were found using the periodogram method of Wehlau & Leung (1964). With the advent of the charge coupled device and the Image Subtraction Method (ISM) of Alard & Lupton (1998) and the method begun by Strader et al (2002), M14 is further surveyed for variables, especially around the crowded cluster core, where few variables have previously been located. Using the above techniques, periods have been verified for 33 previously identified variables. Also, periods have been determined for 5 previously identified variables lacking period assignment, as well as 68 new variables, most of which are RR Lyrae. This paper outlines the method used to locate variable stars in M14, and the results. It also presents background information on variable stars and globular clusters in general.
Here is the thesis in PDF: cjacobs_thesis.pdf (about 1.8 MBytes)