[Mesa-users] Minimum requirement for blue loops for supergiants

[Koushik Sen]

Hi Jeremy,

I ran your inlist in Mesa r10108. I have attached my plot with the mail.

1) You need to set Zbase equal to initial_z in the inlist since you are
using Type2opacities.

2) I ran two models: one with alpha_mlt = 1.73 and the other 1.3. The
models are till the end of He-burning. I do see a blue loop for 1.3 and a
blue hook for 1.73.

It seems to stop due to too many backups high up the Hyashi track.
>

I did not get any problems like this though, the code ran smoothly.

Cheers,
Koushik



>
> On Wed, Apr 10, 2019 at 10:40 AM Koushik Sen <senkoushik1995 at gmail.com>
> wrote:
>
>> Hi Jeremy,
>>
>> I am not an expert on Cepheid variable stars or the instability strip.
>> However, as far as I know, in the stellar models, it is mainly the mixing
>> length parameter that controls the temperature of the Hayashi line
>> (Kippenhahn & Weigert 1990).
>>
>> I could not understand what you meant by very long simulations. You
>> should get blue loops in the core He-burning phase of the stars. So, your
>> stopping condition should be at least till the end of He burning. You can
>> also share the inlists you are using so that we can reproduce your models
>> ourselves.
>>
>> Cheers,
>> Koushik
>>
>> On Wed, 10 Apr 2019 at 16:22, Jeremy Sakstein <sakstein at sas.upenn.edu>
>> wrote:
>>
>>> Thanks Koushik!
>>>
>>> I just tried with alpha_semiconvenction = 10 and so far I am not seeing
>>> any loops. The Hyashi track also seems to be inside the instability strip?
>>> One thing I noticed is that the time-step is very small. Do I need very
>>> long simulations to see these loops?
>>>
>>> Cheers,
>>>
>>> Jeremy
>>>
>>> On Wed, Apr 10, 2019 at 4:31 AM Koushik Sen <senkoushik1995 at gmail.com>
>>> wrote:
>>>
>>>> Hi Jeremy,
>>>>
>>>> You need efficient semi-convection (alpha_semiconvection=1 or higher,
>>>> preferably 10) to get blue loops in this mass range. More efficient
>>>> semiconvection implies more mixing above the He-core, the hydrogen gradient
>>>> gets steeper and steeper H gradients favour more BSGs. The overshooting
>>>> parameter that you are using is fine. The lesser overshooting you use, the
>>>> smaller will be the He core formed, and you'll be more likely to get BSG
>>>> solutions, but even step_overshoot_f_above_burn_h_core=0.11 should be good
>>>> enough if you use alpha_semiconvection = 10. For more details on how
>>>> overshooting and semi-convection affects the evolution of massive stars,
>>>> you can have a look at this paper:
>>>> http://adsabs.harvard.edu/abs/2019arXiv190310423S.
>>>>
>>>> Hope this helps,
>>>>
>>>> Cheers,
>>>> Koushik
>>>>
>>>> On Tue, 9 Apr 2019 at 21:14, Jeremy Sakstein <sakstein at sas.upenn.edu>
>>>> wrote:
>>>>
>>>>> Hi Everyone,
>>>>>
>>>>> I've been trying to get blue loops for supergiant stars (13M and
>>>>> higher) by starting from a preMS model and evolving. My inlist works
>>>>> perfectly for lower mass stars but I don't see the loops for higher masses.
>>>>>
>>>>> I know that these loops are very sensitive to things like overshooting
>>>>> so I was wondering if anyone had an idea of what the minimum controls I
>>>>> need are to see these loops?
>>>>>
>>>>> I am using the default X and Y with initial Z=0.0006. At the moment, I
>>>>> am just turning the Ledoux criterion on and setting
>>>>> alpha_semiconvection=0.1. I tried several different mixing lengths and
>>>>> overshoot fractions (in the range 0.01 to 0.1) but so far I see nothing.
>>>>>
>>>>> I'd be very grateful for any help you can give.
>>>>>
>>>>> Cheers,
>>>>>
>>>>> Jeremy
>>>>> _______________________________________________
>>>>> mesa-users at lists.mesastar.org
>>>>> https://lists.mesastar.org/mailman/listinfo/mesa-users
>>>>>
>>>>>
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