[Mesa-users] How can I insert mass to the core of the star

[Adam Jermyn]

Hi Bear,

It's not currently possible in MESA to say 'I want the new mass to go in position X'. Everything is set up to put the new mass on the surface.

You can probably implement something like this with a run_star_extras though. What I'm imagining is:

* At the start of a particular step (extras_start_step, I think), you reach into the model and change the composition and temperature profiles.

* You then use EOS calls to find the density which makes the pressure profile the same as it was before your change. You can do this using a call to the routine eosPT_get, which implements a root find to get EOS data (including density) at fixed (T,P).

(2) is important because if you just put some cold matter in a model without matching the pressure you'll get strong shocks. I expect that MESA won't like that and suspect that that's not the physics you're interested in. Because hydrostatic equilibrium kicks in faster than thermal equilibrium I think you're always going to be okay pressure-matching, even if you want the material to be cold.

This may or may not work, but it's the closest I could think of to what you're asking!

Cheers,

-Adam

On Thu, Mar 18, 2021 at 5:42 AM, Bear Ealeal < mesa-users at lists.mesastar.org > wrote:

> 
> Hi,
> I want to simulate destruction of a planet near a core of a giant star,
> for that I need to insert mass not in the envelope. When I insert energy I
> can determine where I do it, is it possible with mass?
> Thank you very much for you help,
> Ealeal
> 
> 
> 
> 
> 
> 
> On Thursday, March 18, 2021, 10:42:46 AM GMT+2, Francis Timmes < fxt44@ mac.
> com ( fxt44 at mac.com ) > wrote:
> 
> 
> 
> 
> hi ealeal,
> 
> what scenario are you attempting to model?
> 
> fxt
> 
> 
> 
> 
> > On Mar 18, 2021, at 12:54 AM, Bear Ealeal via Mesa-users < mesa-users@ lists.
> mesastar. org ( mesa-users at lists.mesastar.org ) > wrote:
> >
> > Dear MESA users,
> >
> > I am interested in inserting mass into a star not from the envelope as
> accretion but into the inner parts\core.
> >
> > The "mass_change"  as far as I understand is the opposite button the
> wind, and hence it accretes mass on the envelope.
> >
> > I want to insert mass into the  inner parts of the star and I would also
> like to control the temperature and composition of this mass.
> >
> > How can I do it in MESA? I will appreciate any help,
> >
> > Thank you,
> >
> > Ealeal
> 
> >
> >
> >
> > _______________________________________________
> > mesa-users@ lists. mesastar. org ( mesa-users at lists.mesastar.org )
> > https:/ / lists. mesastar. org/ mailman/ listinfo/ mesa-users (
> https://lists.mesastar.org/mailman/listinfo/mesa-users )
> 
> >
> 
> 
> 
> 
> _______________________________________________
> mesa-users@ lists. mesastar. org ( mesa-users at lists.mesastar.org )
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> 
> 
>
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