Project I

Modulated variability: a new window into stellar pulsations

Richard Anderson

(email advisors)

Unravel the hydrodynamics of stellar pulsations & the structure of stellar atmospheres using high-precision spectroscopy of Cepheid stars!

How can we study the structure of stars in real time? The answer: by investigating how stars vary as a function of time. Cepheids are pulsating supergiant stars whose impressive light variations have important applications as cosmic distance tracers and laboratories for stellar astrophysics. Cepheids change in size by more than a Solar radius in the course of just one week. These violent pulsations induce strong velocity gradients that are accompanied by strange spectral line asymmetries, line splitting, and other interesting features that tell us about the hydrodynamics of stellar atmospheres.

Recently, we discovered that Cepheid variability patterns change over time in an unexpected fashion. Such modulated variability challenges our understanding of Cepheids and may be useful for unraveling the structure and evolution of stars generally. Questions we need to answer include: How regular are the pulsations? What kind of modulations are there? What physical processes affect the way stars oscillate?

In this project, you will work with time series of high-resolution optical spectra of Cepheids to elucidate the mysteries of modulated variability. By modeling different spectral line profiles using multiple components, you will trace the temporal changes in the spectral line shape and atmospheric velocity gradients. In the process, you will learn about the physics of stars and their pulsations, gain experience in programming using python, and work with the highest-quality spectral data of pulsating stars. Finally, we anticipate your results to contribute significantly to a future publication. We look forward to working with you this Summer!

#variablestars  #radialvelocities  #python  #Dopplertomography

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