[Mesa-users] Stationary model

[Pablo Marchant]

Hi Gio, you will have to be much more specific for us to help. If you don't
provide inlists, run_star_extras, or a minimal description of the evolution
stage and the type of star at which you are trying to do this then we
cannot help you. Also without knowing what you actually want to do we can't
help.

On Tue, Nov 13, 2018 at 8:08 AM <g.mirouh at surrey.ac.uk> wrote:

> Hello everyone,
>
> On 13/11/2018 06:04, Pablo Marchant wrote:
> > Hi,
> >
> > depending on what exactly you're trying to do your message could be
> > interpreted in different ways. Something that might be close to what
> > you're looking, is to fix the composition of the star by setting
> >
> > dxdt_nuc_factor = 0d0
> > mix_factor = 0d0
> >
> > the first option will keep the energy input from nuclear reactions,
> > while ignoring the corresponding changes in composition. The second
> > one will remove composition changes due to mixing. You don't want to
> > turn off nuclear reactions, because if you do that the star will
> > simply lose energy and evolve to higher central temperatures in a
> > Kelvin-Helmholtz timescale. If you use these option, you will freeze
> > the evolution of the star if you are dealing with phases in thermal
> > equilibrium. If the starting model is not in thermal equilibrium, then
> > it's trickier.
>
> Thank you Pablo. I implemented these two commands in my inlist, but my
> model is not fixed: when I force the dx/dt to 0, the core brutally
> expands to find some material to burn... and that's not my aim here.
>

Saying that a core expands brutally is very ambiguous. What is brutal to
you? Are you saying it expands in radius? Does the convective core grow in
mass? I mentioned the conditions under which the options I gave you would
work. From your answer I can't really know if those conditions are
satisfied.


> What I want is simply to completely freeze my model at a given
> composition and have it not change anymore. So yes, as you said, I
> literally want to fix the structure variables in the star. I guess it
> sounds simpler than it is actually...
>

You need to be specific about what you actually want to do with the model.
If you literally want to fix the structure variables then by definition any
alteration you do to it would change nothing. So please be specific about
what you want to do and what is the physical motivation for what you're
trying. At this point I don't even know if we're talking about a low mass
star, a white dwarf, something on the main sequence, or a pre-supernova
model.

Cheers


>
> Thanks a lot to anyone who can help.
>
> --
> Gio.
>
>

-- 
Pablo Marchant Campos
M.Sc on Astrophysics, Universidad Católica de Chile
PhD on Astrophysics, Argelander-Institut für Astronomie, Universität Bonn
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