RU Psc: Exploring a Period Shifting, Variable Star

12/06/2019 - 3:30pm to 5:00pm
Speaker(s) / Presenter(s): 
Ron Wilhelm (UK)
Type of Event (for grouping events):

Radially pulsating variable stars found in the instability strip on the H-R Diagram have been known for over a century now. For these stars, the principle mechanism causing pulsation has also been understood for many decades. There remain, however, two pulsation characteristics that have never been fully explained. These are the well-studied, Blazhko Effect and the period shifting variable stars. The former effect causes periodic changes to the maximum brightness of the variable, while the later causes the pulsation period to increase and decrease in a random fashion. Period shifting has not been studied in detail to date and is often assumed to be a by-product of the Blazhko Effect. The period shifting effect has been seen often in large variable star surveys where the period shifting occurs for anywhere between 10 to 30% of the variables surveyed.

I will present light curve results and Fourier analysis of high precision data taken at the MacAdam Student Observatory at the University of Kentucky as well as nine years of data taken at by the Kilodegree Extremely Little Telescope (KELT).   Results show intermittent, non-harmonic frequencies which arise in the KELT data, year-to-year period shifts and a correlation between the size of the compression hump and temporal time delays in maximum light.  I will also present preliminary results from our spectroscopic monitoring program which involves McDonald Observatory and the National Astronomical Observatories of China (NAOC).  This data will allow us to compare radial velocity curves to simultaneous light curves taken from the Transiting Exoplanet Survey Satellite (TESS).  Our ultimate goal is to obtain clues into the underlying physics which is driving the period shift mechanism. 

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