A Long-Term Study of 89 Her: a Pulsating Binary Star
Dr. Bruce Hrivnak
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Arts and Sciences
Since 1994, the astronomy research group at Valparaiso University has been studying the light curves of stars that have evolved beyond the Red Giant stage. For one of these stars, 89 Her, a semi-regular pulsating binary star, we have been collecting brightness data from 1994 to the present time using red (R), visible (V) and blue (B) filters. The intent is to look for periodicity in the data and determining any major periods. Additionally, we included earlier V and B data published by Fernie in order to expand the dataset. We also looked for periodicity in radial velocity data obtained for us in Canada combined with earlier data published by Waters. These periods can be used to determine various properties of the star. From the brightness data in the R and V filters, I have determined one period of approximately 283 days in V and R, a second period of 76.6 days in R and 65 days in the V, and a third period of 67 days in the V. From the radial velocity data, I have determined one dominant period of 290 days and two additional periods of 65 days and 61 days. The longer period of approximately 283 days is thought to be due to light variation arising from interactions with a binary companion. The shorter periods ranging from 60-80 days are due to the pulsation of the main star. This research is supported by grants from the NSF and from NASA through the Indiana Space Grant Consortium.
Morrissey, Christopher C., "A Long-Term Study of 89 Her: a Pulsating Binary Star" (2015). Fall Interdisciplinary Research Symposium. 40.