[mesa-users] Late AGB evolution

[Falk Herwig]

Jefff, this is a know issue. It becomes worse for stars of higher Z and higher mass (2Msun for Z=Z_sun would maybe already be problematic), and if you are resolving all the details of the TP-AGB mixing processes that produce wonderful things like C stars at the right (low) luminosity, and C13 pockets for the s process and so on. If you turn the hydro terms on you will likely see that MESA would like to do very large radial motions which eventually become even supersonic. My interpretation of this is that the condition of the stellar envelope at this point really becomes non-spherical and hydrodynamic, and that this presents another case of "you should really stop 1D and do 3D instead" - which of course is not practical for some goals. One would need to resort to "stellar engineering tricks" at this point, to see if one can reach whatever the science goals of the project are. For certain science goals there are some ideas around for appropriate "tricks". Help to implement them would be appreciated, but it is not clear that they would solve your problem without knowing what exactly your goal is.

Best, Falk.

On 2014-05-22, at 10:29 PM, Jeff Andrews wrote:

> Hello all,
> 
> I'm working on a project testing how different wind mass loss prescriptions and rates affect the evolution from an AGB star into a white dwarf. I've run into a problem evolving the system through loss of the entire hydrogen envelope. It seems like the solvers have real trouble here - as more hydrogen is removed, the time steps decrease due to "newton iters" until they are too small to continue. This happens well before the star becomes a WD. I've tried everything I can think of to help out the solvers, but the stars still don't become WDs.
> 
> I'm using MESA version 6208 with the current SDK. I'm attaching my inlist to evolve a 4 solar mass star.
> 
> Has anyone tried to do something similar? Any help from the community would be really appreciated.
> 
> -Jeff
> <inlist_4.0M_WD>------------------------------------------------------------------------------
> "Accelerate Dev Cycles with Automated Cross-Browser Testing - For FREE
> Instantly run your Selenium tests across 300+ browser/OS combos.
> Get unparalleled scalability from the best Selenium testing platform available
> Simple to use. Nothing to install. Get started now for free."
> http://p.sf.net/sfu/SauceLabs_______________________________________________
> mesa-users mailing list
> mesa-users at lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/mesa-users

--
Falk Herwig
Dept of Physics & Astronomy, U of Victoria
fherwig at uvic.ca, tel: +1 (250) 721-7743