[Mesa-users] Calculating R Parameter (t_HB/t_RGB) in GC by interpolating stellar evolutionary tracks

[Iñigo Muñoz Elorza]

Hi Aaron, all

and many thanks for your answer. Indeed I've been reviewing my analysis an
will have a further systematic look at it. Agree that there's nothing
unusual with models reaching the ZAHB without reaching any specific Teff,
but since I'm trying to replicate the results of previous works using a
different code, I was expecting consistent results. Therefore I was using
the Teff as an indicator.

I have another question that might help me in the next step. In my models,
the position of the ZAHB almost doesn't vary in the HR diagram, despite
increasing the eta_Reimers. Does this might be caused by any parameter that
I'm not activating to take the winds into account during the RGB phase? The
default values for cool_wind_on/off_T, as in controls.default, are
cool_wind_full_on_T = 0.8d4
cool_wind_full_off_T = 1.0d4
If I understand it correct, the cool wind is then relevant below 8000K, and
that's the range where the star is evolving. Is that correct? Having the
cool_wind_full_off_t higher is confusing somehow, but I assumed that it was
affecting only between ON and OFF. Besides that, Is there any other
parameter that I should consider for activating the winds?

Many thanks in advance.

Cheers,
Iñigo

2017-10-18 3:17 GMT+02:00 Aaron Dotter <aaron.dotter at gmail.com>:

> Hi Iñigo,
>
> It seems you have a number of assumptions that are at odds with what the
> models are telling you.  Your best course is to go through each step of
> your analysis and make sure that your results are correct and then check
> whether your assumptions about what "should be" happening are also correct.
>
> You haven't said what the masses of the stars are at the ZAHB.  If the
> masses are similar, then the temperatures may be too.  What happens if you
> increase the Reimers factor again?  Your models may reach the ZAHB (as
> defined by what happens in the core) without reaching a certain Teff at the
> surface.  There's nothing wrong or unusual with that.
>
> I think it would be very good for you to find where the number logT=3.85
> comes from, what exactly it refers to, and how it relates to the models
> you're making.
>
> Please try these suggestions and then, if you have any problems with MESA,
> come back and ask for help.
>
> Cheers,
> Aaron
>
>
>
>
>
>
> On Tue, Oct 17, 2017 at 6:46 PM Iñigo Muñoz Elorza via Mesa-users <
> mesa-users at lists.mesastar.org> wrote:
>
>> OS: macOS SIerra 10.12.5
>> MESA version: r9575
>>
>> Dear community,
>>
>> I'm trying to calculate the R parameter in GC by obtaining the
>> evolutionary tracks of a star of 0.82 Msolar with different eta_Reimers
>> mass loss factors, and then interpolating the solution at Log_T_ZAHB =
>> 3.85, which has been determined by different observational data for that
>> kind of stars.
>>
>> Trying to replicate the results from some previous work by Ayala, I'm
>> considering:
>> - initial_mass = 0.82
>> - initial_Y = 0.248
>> - initial_Z = 0.001
>> - and Reimers_scaling_factor = 0.2 (or 0.35), depending on the case.
>>
>> The problem is that I obtain a value of T_ZAHB lower than 3.85 for both
>> cases, and it should be higher for the case of eta_Reimers = 0.35, but I'm
>> not sure what control parametrs I'm not taking into account.
>>
>> I'm attaching the inlist for both cases, together with the Python script
>> to calculate R. With my current runs, those are my resuts:
>>
>>
>> *eta_Reimers = 0.2*
>> V_ZAHB: 0.549654103615
>> T_ZAHB:  3.71087121492
>> t_HB:  80.6521275821  My
>> t_RGB:  55.9783179064 <(978)%20317-9064>  My
>> R parameter:  1.44077440335
>>
>> *eta_Reimers = 0.35*
>> V_ZAHB: 0.685704604046
>> T_ZAHB:  3.72446361968
>> t_HB:  82.1772995776  My
>> t_RGB:  61.9668190125  My
>> R parameter:  1.32615004106
>>
>> Any ideas why the T_ZAHB are so similar? The t_RGB is also quite
>> different, and should be almost the same for both cases.
>>
>> I have also "experimented" with the parameters modified in the
>> test_suites create_zahb, he_core_flash and hot_cool_wind (opacities, MLT,
>> photospheres), but I haven't seen any improvement on the T issue (of
>> course, the results were different for the different times).
>>
>> Thanks in advance for your support.
>>
>> Cheers,
>> Iñigo Muñoz
>>
>
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