Weekly Update Sep 2 2016, 07:36

I've let madstar lapse for a while. What have I been up to? Here's an update of my activity for the week ending September 2, 2016:

• Re-worked simulations of wave angular momentum in slowly-pulsating B (SPB) stars. Originally, I was appyling the wave torque through a prescribed dOmega/dt. However, if the moment of inertia of the star changes during the torquing process, then it's not guaranteed that the total angular momentum of the star remain zero (as it should, for wave transport). So, it's better to apply the torque through a prescribed dj/dt — and that's what I'm doing, using MESA's other_torque hook. Hopefully, this is the final tweak to the simulations, and I can get the project written up quickly.

• Cooked up and canned batches of sungold tomato relish (recipe here) and habanero/ghost pepper jelly (recipe here; replace jalapeños with habaneros, one ghost pepper and yellow bell peppers). Both damn tasty!

• Visited the Learning Games Network on Science Drive, to discuss the upcoming test of their At Play in the Cosmos game. I'm teaching two sections of Astronomy 103 this semester (400 students total), and we'll be trying out the game as a tool to learn introductory astronomy.

New MESA movies Oct 8 2013, 09:06

Yesterday I uploaded a new set of stellar evolution movies, based on models calculated using MESA. Although still a work-in-progress, these are a big improvement on my old EZ-Web movies, and I hope eventually to build up a complete library showing stars' evolution from cradle to grave.

Dispatches from the Code Front Sep 19 2013, 10:41

I thought I'd post some news on the code development front. So, in brief:

• GYRE is now up to version 2.1.1. A recent improvements is the ability to write text-format output files (by popular demand from MESA Summer School participants!).
• The instrument paper discussing GYRE (Townsend & Teitler 2013) is working its way through MNRAS's publication system. It should be out in a week or two; a preprint is available here.
• The MESA Software Development Kit has seen a few recent updates, which address missing library issues on Linux platforms.
• Nick Hill has a cool working prototype of a code suite for doing spectroscopic modeling on GPUs. This incorporates the GRASSY spectral synthesis code I've been working on, plus the new GLaDOS code Nick wrote, which uses OpenGL to model astrophysical surfaces (e.g., stellar photospheres).
• Chris Bard is making excellent progress on a new arbitrary-field rigid field hydrodynamics (ARFHD) code, and we should be seeing results soon. The code is a generalization of the RFHD code described in Townsend et al. (2007) to allow non-dipole field topologies.
• EZ-Web now supports writing output files in CGS units rather than the usual SI units (much to the relief of Astronomers everywhere!).

New SDK's all round! Jul 24 2013, 19:17

I've just updated both the MESA SDK and the Mad SDK. Both now use the latest (July 24 2013) trunk version of gcc/gfortran, which includes support for Fortran 2003 finalization (nice!) and a fix to a rather nasty memory leak which was plaguing the MESA-GYRE interface. Also, I've hacked the ODEPACK library bundled with the Mad SDK so that it behaves nicely when used with OpenMP.

GYRE is Here Jun 26 2013, 04:10

As I mentioned the a post below, last month I released the first public version of GYRE, the new oscillation code suite I've been developing with Seth Teitler. From the blurb in the abstract of the paper discussing GYRE:

We present a new oscillation code, GYRE, which solves the stellar pulsation equations (both adiabatic and non-adiabatic) using a novel Magnus Multiple Shooting numerical scheme devised to overcome certain weaknesses of the usual relaxation and shooting schemes appearing in the literature. The code is accurate (up to 6th order in the number of grid points), robust, efficiently makes use of multiple processor cores and/or nodes, and is freely available in source form for use and distribution. We verify the code against analytic solutions and results from other oscillation codes, in all cases finding good agreement. Then, we use the code to explore how the asteroseismic observables of a 1.5 M_☉ star change as it evolves through the red-giant bump.

So, there you have it. Work is now underway to develop GYRE further on a number of fronts, including refinement of the entropy calculation in the non-adiabatic code; inclusion of the Coriolis force due to rotation; and integration into MESA's asteroseismic module. Full source code, documentation and related resources can be found here.