I have been working on a project to study the variability of four oxygen-rich proto-planetary nebulae; by their IRAS catalogue names, they are 18095+2704, 19386+0155, 19475+3119, and 17436+5003. Proto-planetary nebulae (PPNe) are evolved stellar objects that are in the process of losing their outer layers and in transition from an asymptotic giant branch star to a planetary nebula. Oxygen-rich PPNe, specifically, have a higher oxygen content in their nebula than they do carbon, and this occurs mainly in lower mass stars. This project includes combining our data from the Valpo Observatory with other published data, analyzing light curves of brightness versus time and looking for patterns, and performing period analysis using a sophisticated period search program called Period04. I began this project in the summer of 2010, and I have successfully analyzed all four of the objects. Over the 16-year observing interval, all of the objects show clear cyclical variations (due to internal pulsation), with periods of 114, 102, 41, and 47 days (in order as listed above); there is also evidence that suggests additional beat periods. Three of the objects show a long-term increase in brightness from anywhere between 5 and 30 percent, while 19475+3119 shows no long-term increase in brightness.
Shaw, Kristie, "The Study of Variability in Four Oxygen-Rich Proto-Planetary Nebulae" (2012). Celebration of Undergraduate Scholarship. Paper 166