[Mesa-users] Extreme helium stars

[AbdelBassit Abdessamed Senhadji]

Thanks Amber !


Exactly what i need.

I want to study the merger of WD but was not sure if mesa can do it. I evolved a simple CO white dwarf as Evan suggested yesterday but was not able to do it in a binary system with another helium core white dwarf.

I will try your suggestion createbtwo pre-merger stars individually and then the post merger and see the resutls.

Thanks
Abdel



________________________________
From: amber lauer <amber.lauer at tunl.duke.edu>
Sent: Thursday, February 15, 2018 9:53:44 AM
To: AbdelBassit Abdessamed Senhadji
Cc: Evan Bauer; mesa-users at lists.mesastar.org
Subject: Re: [Mesa-users] Extreme helium stars

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<mailto: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<mailto:ebauer at physics.ucsb.edu>>
Envoyé : 14 février 2018 13:26
À : AbdelBassit Abdessamed Senhadji
Cc : mesa-users at lists.mesastar.org<mailto: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<mailto: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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--
Amber Lauer
Postdoctoral Researcher
Triangle University Nuclear Lab
Duke University
amber.lauer at tunl.duke.edu<mailto:amber.lauer at duke.edu>
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