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

[Warrick Ball]

Hi Jeremy,

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

Like Koushik, I also didn't have a problem running your inlist, so it 
sounds like your extra code is influencing MESA's results even when it's 
"essentially switched off".

Cheers,
Warrick


------------
Warrick Ball
Postdoc, School of Physics and Astronomy
University of Birmingham, Edgbaston, Birmingham B15 2TT
W.H.Ball at bham.ac.uk
+44 (0)121 414 4552


On Wed, 10 Apr 2019, Jeremy Sakstein wrote:

> Hi everyone,
> 
> One final question if you don’t mind. I’m trying to go to higher masses and the loops seem to be hit or miss. Does anyone have any intuition for how I should vary the over shooting, semi convection, and
> mixing length parameters as I go up in mass?
> 
> Cheers,
> 
> Jeremy 
> 
> On Wed, Apr 10, 2019 at 2:16 PM Jeremy Sakstein <sakstein at sas.upenn.edu> wrote:
>       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
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