[Mesa-users] Extreme helium stars

amber lauer amber.lauer at tunl.duke.edu
Thu Feb 15 09:53:44 EST 2018


Hi Abdel! I was working with a group at LSU that was doing something
similar to this with RCB's which are in the same family as eHe's and are
thought to be a merger of white dwarfs. We discovered several things,
firstly and most important, that MESA is not presently capable of
duplicating a quick merger. In the general sense (SE is not my primary
occupation) it has a hard time with the incredibly fast mass change and is
unable to converge on a stable model. Depending on the mass of the
accretor, the highest MESA can do is 10e-4 - 10e-2 M_solar/per year, when
what you really need is more like 10e4 M_solar per year for just a short
period of time.

The best path would probably be to evolve the two pre-merger stars
individually in MESA (or even in binary) and then note their composition,
and then use stellar engineering to create the post merger star based on
the information you get from the pre merger stars and what you can deduce
they should look like post merger. In my experience this is a pretty
difficult undertaking, but it may be you can piece it together with some
astro-knowledge and the help of the mailing list.

Does this cover what you were trying to accomplish?

On Wed, Feb 14, 2018 at 10:39 PM, AbdelBassit Abdessamed Senhadji <
sen-abd at hotmail.fr> wrote:

> Thank you for your response !
>
>
> Thank you Evan but I already used make_co_wd in the test suite. What i
> want is starting an evolution between two stars:
>
>
> donor star is a C-O WD   and for its companion: a star with a  helium
> core, i want this conditions in the begining of the evolution. Is it
> possible ?
>
>
> Evan, for the pre-made WD models in : data/star_data/white_dwarf_models.
> We can work with them ? i'm not sure if i understand well.
>
>
> Cheers
>
> Abdel
>
>
> ------------------------------
> *De :* Evan Bauer <ebauer at physics.ucsb.edu>
> *Envoyé :* 14 février 2018 13:26
> *À :* AbdelBassit Abdessamed Senhadji
> *Cc :* mesa-users at lists.mesastar.org
> *Objet :* Re: [Mesa-users] Extreme helium stars
>
> Hi Abdel,
>
> There is a case called make_co_wd in the test suite that produces a C/O WD
> at the end of the run. You can produce WDs with different masses by varying
> the parameter initial_mass in inlist_prepare_to_make_co_wd.
>
> MESA also ships a number of pre-made WD models in the following directory:
> data/star_data/white_dwarf_models
>
> Cheers,
> Evan
>
>
> On Feb 14, 2018, at 10:19 AM, AbdelBassit Abdessamed Senhadji <
> sen-abd at hotmail.fr> wrote:
>
> Dear mesa users:
>
> I am currently using mesa-r10108 and last mesa sdk.
>
> I want to reproduce an EHes (Extreme helium stars ). To do that i want to
> evolve a pair of white dwarfs, one with a carbon-oxygen core and the other
> with a helium core.
>
> My questions is : to reproduce that i have to start the evolution with a
> C-O white dwarf ? if yes, how i can start with a C-O WD using MESA ?
>
>
> Cheers,
> Abdel
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>
>
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>


-- 
Amber Lauer
Postdoctoral Researcher
Triangle University Nuclear Lab
Duke University
amber.lauer at tunl.duke.edu <amber.lauer at duke.edu>
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