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

[Jeremy Sakstein]

Hi Aaron,

I do indeed have some extra code but the extra control parameter being zero
essentially switches it off.

Cheers,

Jeremy



On Wed, Apr 10, 2019 at 2:14 PM Aaron Dotter <aaron.dotter at gmail.com> wrote:

> Hi Jeremy,
>
> In addition to Koushik's very helpful response, I noticed that you have
>
> use_other_cgrav=.true.
>
> in your inlist.  If you have some other code that we can't see, it may be
> partially responsible for the problems you're encountering.
>
> Cheers,
> Aaron
>
> On Wed, Apr 10, 2019 at 12:33 PM Koushik Sen via Mesa-users <
> mesa-users at lists.mesastar.org> wrote:
>
>> 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
>>>>>>>
>>>>>>> _______________________________________________
>> mesa-users at lists.mesastar.org
>> https://lists.mesastar.org/mailman/listinfo/mesa-users
>>
>>
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