[Mesa-users] Binaries and wide orbital separation

[Aaron Dotter]

Hi Amedeo,

Your plot shows that the calculated Roche lobe is more than 25,000 Rsun.
You are unlikely to ever make a model with a radius larger than about 1,000
Rsun and so the initial configuration you are considering will never reach
RLOF.

You can estimate the ratio of (Roche lobe)/(orbital separation) using
Eggleton's formula (
https://ui.adsabs.harvard.edu/abs/1983ApJ...268..368E/abstract).  This may
help you to choose the initial values of your simulations.

Aaron

On Mon, Oct 26, 2020 at 10:55 AM Amedeo Romagnolo via Mesa-users <
mesa-users at lists.mesastar.org> wrote:

> Hi Rob, you are right, sorry for not showing plots.
> I believe it happens during the red giant phase , but I don't get which
> kind of problems it might have encountered...
> Here attached the inlists. I tried to keep them as simple as possible.
>
>
> [image: image.png]
>
>
> Cheers,
>
> Amedeo
>
>
> On Mon, 26 Oct 2020 at 09:48, Rob Farmer <r.j.farmer at uva.nl> wrote:
>
>> Hi,
>> It's hard to say what is happening without seeing both your inlists and
>> any plots you have made to show what is going on.
>>
>> When do you reach the min timestep limit? What is your star doing at this
>> time? Is it at the very start of RLOF? Or is it because your star has
>> encountered problems in the core? Or somewhere else? We can't tell unless
>> you make some plots to explore what is going on.
>>
>> Rob
>>
>>
>> On Mon, 26 Oct 2020 at 08:24, Amedeo Romagnolo via Mesa-users <
>> mesa-users at lists.mesastar.org> wrote:
>>
>>> Hi all,
>>>
>>> I have a problem when simulating the evolution of a binary system.
>>> My goal would be to make the more massive star to go into RLOF, which is
>>> easily doable when I'm not setting a wide orbital separation (like a period
>>> in the order of 10^5 yr). In this case, instead, whatever I do, it seems
>>> that the code stops because a too small timestep has been reached, and
>>> therefore the star's radius has no time to grow enough to go beyond its
>>> Roche Lobe radius.
>>>
>>> Do you have any recommendations in this regard?
>>>
>>> Additionally, just another small question: is there an output in MESA
>>> that shows at the end of the simulation the final total metallicity of the
>>> simulated star?
>>>
>>> Thanks in advance,
>>>
>>> Amedeo
>>>
>>>
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