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

[Ebraheem Farag]

Hello Dabasish,

What you're seeing is the result of the input physics, masses, Mass/ratio,
and initial period you've chosen, i.e.all solutions tend to have a minimal
luminosity dip during mass-transfer. Do you need the luminosity to dip?

Aside from changing your initial parameters, an easy way to shortcut this
is, albeit less-physical, is to evolve primary on its own until H-depletion
in star and then load in the saved model to binary with the desired initial
period.

-EbF

On Tue, May 30, 2023 at 11:58 AM Debasish Dutta <debasishdutta1707 at gmail.com>
wrote:

> I forgot to mention in the first email: if I decrease the orbital period,
> I get case A mass transfer. The mass transfer starts when the star is still
> burning hydrogen in its core. So I had to go to a larger orbital period,
> but then I begin to get a mass transfer phase where the luminosity dip is
> small.
> ᐧ
>
> On Tue, 30 May 2023 at 20:14, Ebraheem Farag <ekfarag at asu.edu> wrote:
>
>> 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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