Searching for Periodicity in Proto-Planetary Nebulae

Faculty Sponsor

Bruce Hrivnak


Astronomy, Physics, Stellar Evolution

Presentation Type

Oral Presentation

Symposium Date

Spring 4-29-2021


Our research revolved around analyzing how the brightness of proto-planetary nebulae (PPNe) vary over time. The overall goal was to analyze their light curves for periodicity and to find what the periods are if they exist. PPNe are low mass stars in transition from the red giant and Asymptotic Giant Branch (AGB) phase to the planetary nebula phase of a star’s life cycle. This transition is known to last only a few thousand years. Similar to AGB stars, PPNe pulsate causing them to periodically vary in brightness. However, we do not have as much data on PPNe nor do we have as good of an understanding of the mechanics of their pulsation. To analyze our PPNe candidates for periodicity, we gathered data from the All-Sky Automated Survey for Supernovae (ASAS-SN). We then used these data to construct light curves for each of our candidates. After eliminating the data of poorer quality, we analyzed them using a program called Period04, which uses a Fourier transform to search for periods and allowed us to fit sine curves to the data. We studied a sample of 18 PPNe candidates located in the southern celestial hemisphere. Most of them were found to have periods ranging from around 20 - 120 days, with several PPNe having multiple periods. Several PPNe also had long-term (multi-year) trends to their brightness variations. Our results can be used to better understand the structure and evolution of stars in this phase of their life cycle. This research was supported by a grant from NASA through the Indiana Space Grant Consortium.

Biographical Information about Author(s)

Sean Egan and Peyton Grimm are both Sophomore Physics majors at Valparaiso University. Both are highly interested in Astronomy. During the summer of 2020, they received an internship under professor Hrivnak to study proto-planetary nebulae. They are looking forward to seeking out new experiences and research in the field of Astronomy. Sean Egan and Peyton Grimm both plan on obtaining their PhDs later in life.

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