Study of the Pulsations of the Semiregular Variable Stars

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AST 0307281Buchler, J. RobertIrregularly pulsating stars stretch from the so-called W Vir type stars through the RV Tau and Semi-regular stars all the way into the long period Mira variable star region. In this project, a thorough, novel analysis of observational lightcurve data and a systematic numerical modeling survey of the pulsational properties of these stars is underway. These bright variable stars are playing an increasingly important role in the observational study of star clusters and dwarf galaxies where standard candles such as classical Cepheid variables may be rare. The goal is to extract unique, quantitative information from the irregular lightcurves. A test is also planned of the hypothesis that a single resonant mechanism is at the heart of the irregular pulsations of these stars. Further, the study will shed new light on the uncertain evolutionary status of these stars. New observational data, novel methods of analysis adapted from nonlinear dynamics, and progress in numerical convective hydrocodes lend this study a timely status.The project has a broader impact, because the techniques being developed are very useful in other research areas as well, ranging from astronomy to nonlinear dynamics to medicine. Thus two of the codes are being made user-friendly and publicly accessible: TIFRAN, the time-frequency analysis, that has medical applications as a diagnostic tool for speech disorders, otolaryngology and neurology among other things, and FLOWRECON, the flow reconstruction from a time-series with wide applications in nonlinear dynamics research. A popular website on radially and nonradially pulsating stars with audio and video is being constructed with the help of two undergraduate students. The teaching of the large undergraduate noncalculus physics class provides the investigator with the opportunity to bring astrophysics, and this research in particular, to the classroom.