Presentation #204.06 in the session Pulsating Variable Stars — iPoster Session.
Protoplanetary-nebula (PPNe) are stars in the stage of stellar evolution that falls between the asymptotic giant branch and planetary nebula (PNe) stages. Most PPNe display cyclical variations in their brightness due to pulsations. In an earlier study of 12 carbon-rich PPNe, periods were found for all of the objects, ranging from 38 to 153 days (Hrivnak et al. 2010, ApJ 709, 1042). In this present study, we have analyzed newer and more precise data for 6 of these objects. Observations were obtained at the Valparaiso University Observatory (2008 to 2018) in the V and r filters. In addition, we have used observations from the All-Sky Automated Survey for Supernova (ASAS-SN; 2016 to 2021) first in the V and then in the g filter. While these later cover shorter intervals of time, they have much denser coverage. These datasets separately and in combinations were analyzed using PERIOD04. Primary and secondary periods were found for each object. The results of the primary periods are generally similar to those of the earlier study. We also investigated possible period changes. This research is supported by a grant from the National Science Foundation (1413660).