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Stars on the Verge: Analyzing Long-term Photometry of Galactic Red Supergiant SN-II Progenitors

Presentation #204.11 in the session Pulsating Variable Stars — iPoster Session.

Published onJun 29, 2022
Stars on the Verge: Analyzing Long-term Photometry of Galactic Red Supergiant SN-II Progenitors

Red supergiant (RSG) stars are evolved, luminous, moderately massive stars nearing the end of their lives. RSGs are the common progenitors of Type II core-collapse supernovae. As a result, RSGs are crucial keys to astrophysics because during both their supergiant phase and death they process and eject heavier elements into the interstellar medium as well as heating it. These stars are known for slow semi-regular light variations, generally attributed to pulsations, with semi-regular variability likely also caused by large convection cells and large spots. RSGs generally vary with two dominant periods (see Kiss et al. 2006), typically a short period of a few hundred days, and long period up to several years. This semi-regularity permits measurement and analysis of their periods of these light variations, as well as how these periods change over time.

Analysis of a sample of 21 RSGs was undertaken using the Peranso-3 period program suite. The period analyses were performed on observations often dating back over a century, obtained mostly via the American Association of Variable Star Observers (AAVSO) and the British Astronomical Association (BAA) and the Harvard Astronomical Photographic Plate Archive. The CLEANest software was used to initially determine the dominant periods for each star. Where warranted, the Weighted Wavelet Z-Transform (WWZ) program was used to study the evolution of the light variations and periods over time. The calculated dominant periods and period changes for each star were compared with the star’s physical properties (e.g., L/Lo, MK, Mass, Teff, age…) to investigate possible relationships. The initial results are presented and discussed with focus on some of more interesting stars in the sample such as Betelgeuse and Antares.

This research is supported by a Villanova Undergraduate Research Fellowship (VURF) which we gratefully acknowledge. We also thank the countless observers (past and present — most of which are amateur astronomers) who carried out the observations and to the AASVO and BAA for archiving these important archival datasets.

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