Presentation #204.07 in the session Pulsating Variable Stars — iPoster Session.
In this project, we analyzed the light curves of 5 carbon-rich proto-planetary nebulae (PPNe) with the goal of improving their periods and investigating period change. PPNe are stars late in their evolution, in transition between the asymptotic giant branch stage and the planetary nebulae stage. They are known to pulsate, and some have been found to have multiple periods to their pulsation. The goal of this research is to find these periods so that we may better understand the internal properties of PPNe. Our earlier study (Hrivnak et al. 2010, ApJ, 709, 1042) found all five of our stars to vary periodically. New light curves were obtained at the Valparaiso University Observatory (2008–2018) in the V and R filters, and we made use of data from the All-Sky Automated Survey for Supernovae (2014–2021) in the V and g filters. These new light curves were analyzed individually and in various combinations to search for periods using Period04. Periods were found for all five of these stars. For three of them, a second period was found. The periods for these stars range between 30 and 240 days. None of the stars show evidence for long-term (multi-year) periods which might have been evidence for binarity. This research is supported by an NSF grant (1413660).