Re: [mesa-users] very thin shell burning

[Kent B. <kg...@la...>]

This is exactly the kind of thing that has piqued my interest. It looks
like it might be a fruitful topic for research for me.

On Tue, 2011-03-29 at 23:25 -0700, Falk Herwig wrote:
> On 8-Mar-11, at 9:55 AM, Kent Budge wrote:
> 
> > So I'm running some Population III calculations at the lower end of  
> > the
> > mass range, and the very thin shell burning on the giant branch is
> > taking *forever*.
> >
> > What's the latest thinking about mass loss in Population III? I know
> > it's thought to be rather low, but just how rather low?
> 
> I think that really depends on the type of stars. There is common  
> scaling out there in which Mdot ~ sqrt(Z) but that applies only to  
> mass loss processes that are driven by radiation pressure on lines,  
> and if there is no self-enrichment of the surface. For AGB stars both  
> assumptions are wrong, since AGB stars will bring lots of C, O and  
> other metals to the surface. I am not an expert on dust formation, but  
> I think it is not clear that in particular in the C-rich phase for  
> advance AGB stars, even at Pop III you could not have effective dust  
> formation, which would activate the characteristic dust-driven wind  
> mechanism of AGB stars. Observations seem to indicate at least that in  
> the MCs Mdot is not smaller than in the Galaxy.
> 
> >
> > What is the state of the art in modeling very thin shell burning?  
> > Brute
> > force seems, well, like brute force. Are there methods out there that
> > treat it as a front propagation problem?
> >
> 
> In Pop III AGB stars or even very low metallicity AGb stars you will  
> encounter convective-overshoot induced H-flame propagation into the  
> core when the convective envelope gets in touch with the hot CO core.  
> This is not the regular H-shell in AGB stars, but rather a hot dregde- 
> up after thermal pulses. That is a situation where a flame model would  
> be needed, but I believe we have not much right now to base this on.  
> Note that this is a flame across a fuel-mix boundary.
> 
> BEst, Falk.
> 
> > Interested in any information anyone has.
> >
> > -- Kent G. Budge
> > CCS-2, LANL
> >
> >
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> --
> Falk Herwig
> Dept of Physics & Astronomy, U of Victoria
> fh...@uv..., tel: +1 (250) 721-7743
> 
> 
> 
--