[Mesa-users] Case B mass transfer at solar metallicity

[Ebraheem Farag]

Hello Debasish,

> There is a mass transfer, but what I was worried about is that during the
mass transfer phase, we should have observed a luminosity dip, but here we
cannot see any significant luminosity dip during mass transfer.

It's there, just not very large on the scale of your hr diagram, since your
initial orbital separation is very large. The decrease in luminosity during
mass-transfer is a result of thermal disequilibrium of the primary (donor).
On the RGB/AGB the thermal timescale of the primary can be as much as ~ 1
order of magnitude lower as compared to the main-sequence. Therefore a
stronger mass-transfer rate, perhaps due to a lower initial orbital
separation, is necessary to bring the star farther out of thermal
equilibrium and induce a large luminosity dip.

Decreasing the initial orbital period 'initial_period_in_days', should
increase size of the luminosity dip in the hr.

-EbF

On Tue, May 30, 2023 at 7:22 AM Debasish Dutta via Mesa-users <
mesa-users at lists.mesastar.org> wrote:

> Hi Ebraheem,
>
> Thank you very much for your reply. There is a mass transfer, but what I
> was worried about is that during the mass transfer phase, we should have
> observed a luminosity dip, but here we cannot see any significant
> luminosity dip during mass transfer. That was what I meant by a weird HR
> diagram.
>
> Regards
> Debasish
> ᐧ
> ᐧ
> On Tue, 30 May 2023 at 18:49, Debasish Dutta <debasishdutta1707 at gmail.com>
> wrote:
>
>> Hi Ebraheem,
>>
>> Thank you very much for your reply. There is a mass transfer; but what I
>> was worried about is that during the mass transfer phase, we should have
>> observed a luminosity dip, but here we cannot see any significant
>> luminosity dip during mass transfer. That was what I meant by a weird HR
>> diagram.
>>
>> Regards
>> Debasish
>> ᐧ
>>
>> On Mon, 29 May 2023 at 13:07, Ebraheem Farag <ekfarag at asu.edu> wrote:
>>
>>> Hello Debasish,
>>>
>>> I'm guessing that by case B mass transfer you mean mass transfer which
>>> occurs while the donor is in or evolving toward the Red Giant branch.
>>> In that case I believe this is exactly what you are observing. You have
>>> a system where M1 (donor) > M2 (BH) when mass transfer begins, as M1
>>> evolves to the RGB, the envelope expands, fills its Roche-lobe and begins
>>> stable mass-transfer resulting in an increase in orbital separation until
>>> the binary completely detaches ( mass-transfer approaches 0). The donor
>>> star (M1) then continues its normal evolution, with wind driven mass-loss
>>> stripping the remaining envelope, leaving as a hot exposed helium core at
>>> helium depletion (a wolf-rayet star).
>>>
>>> Hopefully this answers your question.
>>>
>>> -EbF
>>>
>>> On Sun, May 28, 2023 at 11:18 AM Debasish Dutta via Mesa-users <
>>> mesa-users at lists.mesastar.org> wrote:
>>>
>>>> Hi,
>>>> I am trying to evolve a binary system with a black hole companion. I am
>>>> interested in getting a Case B mass transfer. For lower metallicity models
>>>> (SMC, LMC and Zsun/10), it seems to work well. However, for higher
>>>> metallicity (~solar) massive models, I could not get the Case B mass
>>>> transfer. I was using the initial orbital periods as 70 days for the lower
>>>> metallicity models. In the case of solar metallicity, if I use an extended
>>>> period (~450 days), I get some weird HR diagrams with the mass transfer
>>>> phase almost non-existent. I  have attached my inlists and also a HR
>>>> diagram of a 42 solar mass model at solar metallicity (mass ratio=0.6).
>>>>
>>>> I would be glad if someone could help me regarding this.
>>>>
>>>> Regards
>>>> Debasish
>>>> ᐧ
>>>> _______________________________________________
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