• Asteroseismology of the evolved star Procyon (with Bedding et al.): The evolved star Procyon is in a very interesting stage of its evolution, near the end of core hydrogen burning. Accurate measurement of a substantial number of oscillation frequencies will provide strong constraints on the evolution of intermediate- mass stars in this phase, including the effects of the convective core and possibly convective overshoot and/or rotational mixing. We will obtain time- series radial velocity observations of Procyon using the Coude spectrograph and I2 cell on McDonald Observatory's 2.7-m telescope. These observations will be conducted as part of a multi-site campaign to resolve unambiguously the individual oscillation frequencies in this star, and to determine its age and internal structure.

• Magnetic Activity Cycles of Southern Sun-like Stars (with Henry, Knölker & Soderblom): The solar magnetic activity cycle is responsible for periodic episodes of severe space weather, which can perturb satellite orbits, interfere with communications systems, and bring down power grids. Much progress has recently been made in forecasting the strength and timing of this 11-year cycle, using a predictive flux-transport dynamo model. We can strengthen the foundation of this model by extending it to match observations of similar magnetic activity cycles in other Sun-like stars, which exhibit variations in their Ca II H and K emission on time scales from 2.5 to 25 years. This broad range of cycle periods is thought to reflect differences in the rotational properties and the depth of the surface convection zone for stars with various masses and ages. Asteroseismology is now yielding direct measurements of these quantities for individual stars, but the most promising asteroseismic targets are in the southern sky (α Cen A, α Cen B, β Hyi), while the existing activity cycle survey is confined to the north. We have proposed to initiate a long-term survey of Ca II H and K emission for a sample of 92 southern Sun-like stars to measure their magnetic activity cycles and rotational properties, providing independent tests of solar dynamo models.

Computational

• Asteroseismology of Sun-like Stars (with Christensen-Dalsgaard & Brown): Asteroseismology provides a unique opportunity to probe the internal structure of pulsating stars, by matching the observed oscillation frequencies with stellar models. Several current and planned satellite missions will soon yield observations of revolutionary quality for dozens of pulsating stars. Deriving reliable seismological constraints from these data will require a significant improvement in our analysis methods. I propose to calibrate the structure and evolution of Sun-like stars by undertaking a massive computational exploration of seismological models, to fit existing observations and forthcoming space-based data. This work will make use of a proven analysis method, based on a parallel genetic algorithm, that I developed for white dwarf asteroseismology.

• A Deeper Understanding of White Dwarf Interiors: A detailed record of the physical processes that operate during post-main-sequence evolution is contained in the internal chemical structure of white dwarfs. Global pulsations allow us to probe the stellar interior through asteroseismology, revealing the signatures of prior nuclear burning, mixing, and diffusion in these stars. I review the rapid evolution of structural models for helium-atmosphere variable (DBV) white dwarfs over the past five years, and I present a new series of model-fits using recent observations to illustrate the relative importance of various interior structures. By incorporating physically motivated C/O profiles into double-layered envelope models for the first time, I finally identify an optimal asteroseismic model that agrees with both diffusion theory and the expected nuclear burning history of the progenitor. I discuss the implications of this fundamental result, and I evaluate the prospects for continued progress in the future.

Theoretical

• Asteroseismic Signatures of Stellar Magnetic Activity Cycles (with Dziembowski, Judge & Snow): Observations of stellar activity cycles provide an opportunity to study magnetic dynamos under many different physical conditions. Space-based asteroseismology missions will soon yield useful constraints on the interior conditions that nurture such magnetic cycles, and will be sensitive enough to detect shifts in the oscillation frequencies due to the magnetic variations. We derive a method for predicting these shifts from changes in the Mg II activity index by scaling from solar data. We demonstrate this technique on the solar-type subgiant beta Hyi, using archival International Ultraviolet Explorer spectra and two epochs of ground-based asteroseismic observations. We find qualitative evidence of the expected frequency shifts and predict the optimal timing for future asteroseismic observations of this star.

• The Future of Computational Asteroseismology (invited review): The history of stellar seismology suggests that observation and theory often take turns advancing our understanding. The recent tripling of the sample of pulsating white dwarfs generated by the Sloan Digital Sky Survey represents a giant leap on the observational side. The time is ripe for a comparable advance on the theoretical side. There are basically two ways we can improve our theoretical understanding of pulsating stars: we can improve the fundamental ingredients of the models, or we can explore the existing models in greater computational detail. For pulsating white dwarfs, much progress has recently been made on both fronts: models now exist that connect the interior structure to its complete evolutionary history, while a method using parallel computers for global exploration of relatively simple models has also been developed. Future advances in theoretical white dwarf asteroseismology will emerge by combining these two approaches, yielding unprecedented insight into the physics of diffusion, nuclear burning, and mixing.