GYRE 5.2 released Apr 26 2018, 21:00

A few days ago, I released version 5.2 of my GYRE oscillation code. This is the sixteenth release of the code, and coincided with the successful launch of NASA's Transiting Exoplanet Survey Satellite (TESS). I'm hoping that GYRE will become the standard tool for analyzing TESS observations of stellar oscillations; certainly, over the past few weeks, I've noticed an uptick in the number of new users at the GYRE Forums, with the total number of registered users now approaching 100. Exciting times are ahead!

So, what's new in version 5.2? Most of the significant changes have taken place deep in GYRE's internals, with much-needed improvements to speed and stability. Users will notice a few bug fixes, but the next big leaps in functionality — new algorithms for finding highly non-adiabatic modes, and the ability to model dynamical tides — will have to to await the release of GYRE 6.0, later in 2018.

MESA IV: Convection, Diffusion and Explosions, Oh My! Oct 20 2017, 16:14

Last week I was out in Santa Barbara, working with other developers on finalizing the 4^th MESA instrument paper (see here, here, and here for the first three instrument papers). My contribution to this 63-page tome center around the correct treatment of convective boundaries. I've been working on this topic since the KITP Massive Stars program in Winter/Spring 2017, when my friend and colleague Anne Thoul got me interested. Since then, Anne and I have developed a new predictive mixing scheme, which fixes previous issues in MESA with the location and growth of convective boundaries.

As well as describing the predictive mixing scheme, the instrument paper introduces new capabilities for treating elemental diffusion under degenerate conditions, and for modeling core-collapse supernovae. The paper was submitted to the Astrophysical Journal earlier this week, and will appear on the arXiv next week.

Compiling ffmpeg on OSX Jun 15 2017, 15:19

While rolling a new release of the MESA SDK, I've finally stumbled on the magical invocations necessary to compile the ffmpeg video encoder/decoder on recent releases (10.10 and beyond) of Mac OSX. The problem lies with headers for various OSX frameworks, which cause the gcc compiler to barf. The solution is to disable usage of these frameworks when configuring ffmpeg; specifically, configure with the following flags:

I've not seen this workaround elsewhere on the web (almost all discussions of ffmpeg on OSX focus on homebrew installation); so, I thought I would post it here in the hope that someone might benefit.

Farewell to KITP Massive Stars May 31 2017, 14:21

Earlier this month I returned from the Massive Stars program at the Kavli Institute for Theoretical Physics. Speaking personally, the program was a huge success; I met many awesome people, got involved in a number of new projects, and decided that I Rather Like the West Coast! Here's a sample of some of the papers which will emerge from this incredible experience:

• Angular momentum transport by heat-driven g-modes in slowly pulsating B stars (with Jacqueline Goldstein and Ellen Zweibel; submitted to MNRAS)
• The Tayler Instability in the Anelastic Approximation (with Jacqueline Goldstein and Ellen Zweibel; to be submitted to MNRAS)
• Super-Eddington stellar winds: unifying radiative-enthalpy vs. flux-driven models (with Stan Owocki and Eliot Quataert; to be submitted to MNRAS)
• A paper on pulsation instabilities in supersoft sources (with Bill Wolf and Lars Bildsten; in preparation)
• A paper on new MESA capabilities (with Anne Thoul and the rest of the MESA team; in preparation)

Now that I'm back in Madison, I'm scrambling to get all these papers out the door — and to push ahead with releasing version 5.0 of GYRE, which is long overdue.

Massive stars come to KITP Feb 26 2017, 18:52

I'm out in Santa Barbara for the next 11 weeks, helping to organize (and participate in) the Massive Stars program occurring at the Kavli Institute for Theoretical Physics. I'm hoping this time away from Madison will give me a chance to reboot mad star and write about some of the cool stuff I've been working on over the past couple of years.

In addition to meeting and working with some of the world's greatest stellar astrophysicists (including my old boss and buddy Stan Owocki), I hope to achieve at least some of the following goals:

• Finish writing the new user guide for GYRE, so I can finally get release 5.0 officially out of the door.
• Create new releases of the MESA SDK (and Mad SDK), amongst other things bringing the gfortran compiler up to date.
• Get my YARG code working again, so I can finish up a project on massive star wind polarization that I started years ago with Nick Mast (now a grad student at Minnesota).
• Complete a too-long-in-the-works paper with Jacqueline Goldstein and Ellen Zweibel, demonstrating that heat-driven g modes can rapidly alter the internal rotation profiles of slowly pulsating B stars.
• Hang out with Bill Paxton (the living one, not the sadly departed one) and other MESA developers, to work on the next release of the code.

By the way, the picture is a jar of my double-trouble habanero jelly. I made a batch last week, and brought it with me. One jar is promised to Frank Timmes, the others will likely be used (in anger!) as prizes for program participants.