Exploring multimode pulsation in classical cepheid stars

Abstract

The objective of this research project is to put forth a mechanism for why certain Cepheids develop multimode pulsation. This was accomplished using computer simulations to model a classical Cepheid star which exhibits these pulsation patterns. The majority of classical Cepheids, important distance candles in astronomy, pulsate in either the fundamental or first overtone. However, a small but significant minority appear to display a frequency modulated with a higher overtone. There is no currently accepted hypothesis as to why. This research project used a combination of software suites to simulate stellar evolution, and energy, density, and material flow within the star. A 7 solar mass model began displaying clear pulsation, and Fourier analysis of the luminosity data also suggests higher overtones are present. This model also displays gravity waves and spherical harmonics within the star which may provide clues as to why this behaviour develops. Still, several discrepancies exist between predicted behaviour and modeled behaviour