The Beginnings and Ends of Double White Dwarfs

I’m in Copenhagen, Denmark for a conference I organized on The Beginnings and Ends of Double White Dwarfs. I’m giving a talk entitled The Long-Lived Remnants of Massive WD Mergers.

Ninth Meeting on Hot Subdwarfs and Related Objects

I’m in Hendaye, France for the Ninth Meeting on Hot Subdwarfs and Related Objects. I’m giving a talk entitled The Formation and Evolution of R Coronae Borealis Stars. I also presented a poster entitled Helium star donors to thermonuclear supernovae discussing work led by Sunny Wong.

Sunny Wong wins Steck Award

Sunny Wong, an undergraduate working with me, received the Steck Family Award for the Finest Senior Thesis at UC Santa Cruz for his thesis “Evolution of Helium Star - White Dwarf Binaries Leading up to Thermonuclear Supernovae”. This work is also described in his first author paper of the same name.

Electron-Capture-Initiated Stellar Collapse

I’m in Leiden, NL at the Lorentz Center for a workshop I helped organize on Electron-Capture-Initiated Stellar Collapse.

Modules for Experiments in Stellar Astrophysics (MESA): Pulsating Variable Stars, Rotation, Convective Boundaries, and Energy Conservation

The Astrophysical Journal Supplement Series, Volume 243, Issue 1, article id. 10, 44 pp

Bill Paxton, R. Smolec, Josiah Schwab, A. Gautschy, Lars Bildsten, Matteo Cantiello, Aaron Dotter, R. Farmer, Jared A. Goldberg, Adam S. Jermyn, S.M. Kanbur, Pablo Marchant, Anne Thoul, Richard H. D. Townsend, William M. Wolf, Michael Zhang, F.X. Timmes

We update the capabilities of the open-knowledge software instrument Modules for Experiments in Stellar Astrophysics (MESA). RSP is a new functionality in MESAstar that models the non-linear radial stellar pulsations that characterize RR Lyrae, Cepheids, and other classes of variable stars. We significantly enhance numerical energy conservation capabilities, including during mass changes. For example, this enables calculations through the He flash that conserve energy to better than 0.001 %. To improve the modeling of rotating stars in MESA, we introduce a new approach to modifying the pressure and temperature equations of stellar structure, and a formulation of the projection effects of gravity darkening. A new scheme for tracking convective boundaries yields reliable values of the convective-core mass, and allows the natural emergence of adiabatic semiconvection regions during both core hydrogen- and helium-burning phases. We quantify the parallel performance of MESA on current generation multicore architectures and demonstrate improvements in the computational efficiency of radiative levitation. We report updates to the equation of state and nuclear reaction physics modules. We briefly discuss the current treatment of fallback in core-collapse supernova models and the thermodynamic evolution of supernova explosions. We close by discussing the new MESA Testhub software infrastructure to enhance source-code development.