Pulsating stars as probes of stellar astrophysics
and calibrators for the cosmic distance ladder
(page under construction, Dec 2018)
My research focuses on the evolution of stars and the cosmos. Specifically, I work to improve cosmic distance measurements in order to measure the current expansion rate of the Universe with maximum accuracy. In so doing, I hope to contribute to an understanding of dark energy, which makes up 75% of the Universe's energy density and accelerates its expansion. At the same time, I am very interested in the physics of stars, their variability and evolution with time. In particular, I investigate how rotation and interactions in binary star systems can impact the way stars evolve. A better understanding of these processes gives us a firmer grip on the lifetimes and ages of stars, on their luminosities, and the availability of the building blocks of life (carbon, nitrogen, and oxygen) in galaxies.
To these ends, I investigate the astrophysical properties and distance applications of classical Cepheid variable stars using observational and theory-based approaches. These stars are uniquely suited for my research, because they are at once cosmic yardsticks and sensitive stellar laboratories. Some of the objects I have investigated are even visible to the naked eye, such as the prototype δ Cephei and the North Star, Polaris.
Calibrating the Cosmic Distance Scale
Highly accurate extragalactic distances are required to measure the expansion rate of the Universe and understand dark energy. My work seeks to reduce bias and increase the accuracy of such distances.
The figure shows bias due to stellar association (Anderson & Riess 2017).
Rotation and stellar evolution
Evolved pulsating stars are sensitive laboratories for state-of-the-art theoretical models, in particular to investigate the effects of rotation on stellar evolution. The figure illustrates the age discrepancy for Polaris (the North Star) and its companion (Anderson 2018).
High-precision velocimetry of pulsating stars
This technique is revealing new aspects of pulsations and their interactions with stellar atmospheres, see Anderson (2017) for a review. The figure shows cross-correlation functions of l Carinae (Anderson 2016).
Gaia, Binaries, Modulations, Asteroseismology, etc.
Stay tuned for more information to come...