[Mesa-users] Setting subsolar/supersolar metallicity

Tue May 7 17:30:27 UTC 2024

Hi Ebraheem,

Once again, thank you very much for the detailed clarification. It is
beneficial for all, I think.

With regards,
Amar

On Wed, May 8, 2024 at 12:53 AM Ebraheem Farag <ekfarag at asu.edu> wrote:

> Hi Amar,
>
> 1 - Yes, I would recommend using identical 'intial_zfracs' and not
> thinking further about it unless you have plans for adjusting the initial
> network composition.
>
> 2 - There are two mixtures communicated in Asplund et al. 2009, one is the
> photospheric mixture, and the other is meteoric mixture (there is some
> overlap for individual elements). MESA adopts the photospheric mixture not
> the meteoric mixture, therefore the total metallicity for the reference
> initial_zfracs = 6 is lower "0.0134"(photospheric) than it would otherwise
> be "0.0142" (meteoric). This is a result of heavy element diffusions
> (gravitational settling) of heavier elements over the lifespan of the Sun.
>
> MESA adopts the current solar photospheric mixtures, and it is a normal
> practice to scale the value of 0.0134 up to 0.0142 to achieve metal mass
> fractions that are approximately equal to the meteoric values. This is in
> effect what is being communicated in the MIST 1 paper.
>
> -EbF
>
> On Mon, May 6, 2024 at 8:54 PM Amar Aryan <amararyan941 at gmail.com> wrote:
>
>> Hello Ebraheem,
>>
>> Thank you so much for detailing the process of setting the metallicity
>> and corresponding opacities.  I have a few more queries:
>>
>> 1) Can we use a single initial_zfracs (for e.g., asplund mixture by
>> setting initial_zfracs = 6) for both subsolar (for e.g., initial_z =
>> 0.71d-2) and supersolar (for e.g., initial_z = 2.82d-2) metallicity models?
>>
>> 2)  It is mentioned in section 3.1 of Jieun Choi et al. 2016 (MIST 1)
>> <https://urldefense.com/v3/__https://iopscience.iop.org/article/10.3847/0004-637X/823/2/102__;!!IKRxdwAv5BmarQ!YhnrtvzGVVoiMGnHA27SCzWlR4E3PBXVDzostU9iJYMKwYmwyS3jE7hsgBO4HdxNhgkYA24DvfYUD7CbkpNSb37rKQ$>
>> . "In other words, [Z/ H] is computed with respect to Z = Z,protosolar =
>>  0.0142, not Z = Z,photosphere = 0.0134." However, when I looked in the
>> "mesa-r24.03.1/chem/public/chem_def.f90" file, it sets "real(dp), parameter
>> :: AGSS09_zsol = 0.0134d0" in line no 280. I think AGSS09 is from asplund
>> 2009 (set by initial_zfracs = 6, in inlist_mass_Z_wind_rotation), so the
>> definition should be  "real(dp), parameter :: AGSS09_zsol = 0.0142d0."
>>  Please confirm if it is OK.
>>
>> With regards,
>> Amar
>>
>> On Tue, May 7, 2024 at 1:26 AM Ebraheem Farag <ekfarag at asu.edu> wrote:
>>
>>> Hi Amar,
>>>
>>> For deciding initial_y, It's typical to scale the abundances using a
>>> scaling formulation like the one in section 3.1 of Jieun Choi et al.
>>> 2016 (MIST 1)
>>> <https://urldefense.com/v3/__https://iopscience.iop.org/article/10.3847/0004-637X/823/2/102__;!!IKRxdwAv5BmarQ!YhnrtvzGVVoiMGnHA27SCzWlR4E3PBXVDzostU9iJYMKwYmwyS3jE7hsgBO4HdxNhgkYA24DvfYUD7CbkpNSb37rKQ$>.
>>> Although you can choose to increase the value of Z at constant Y, just know
>>> that these are not the same choices.
>>>
>>> The initial_zfracs should not change. You are scaling the total
>>> abundance, not the abundance of each individual isotope. The only time in
>>> which you would change the initial_zfracs is when you are intentionally
>>> trying to change the composition of the network at fixed Z. If you change
>>> the initial_zfracs, you need to also be sure that you are using the correct
>>> lowT, highT, and CO enhanced opacity tables that correspond to the desired
>>> mixture you are choosing. In your case, the agss09 opacities are selected
>>> in 'inlist common':
>>>
>>> &kap
>>>       ! OPAL asplund 2009 opacities, Zbase set in
>>> inlist_mass_Z_wind_rotation
>>>       kap_file_prefix = 'a09'    ! 'gs98' 'a09'  'OP_a09' 'OP_gs98'
>>>       kap_CO_prefix   = 'a09_co' ! 'gs98_co' 'a09_co'
>>>       kap_lowT_prefix = 'lowT_fa05_a09p'
>>>       use_Type2_opacities = .true.
>>>
>>> / ! end of kap namelist
>>>
>>> The default in mesa is initial_zfracs = 3 ! gs98 abundances, and the
>>> default opacity tables are also for a gs98 mixture. We opt for the asplund
>>> mixture in this test_suite.
>>>
>>> Let this thread be a psa to all who read the mailing list: always ensure
>>> you are using the correct values of initial_zfracs which corresponds to the
>>> opacity/kap tables you have selected. Initial_zfracs can only be modified
>>> at the beginning of a run when the model has a uniform mixture, so this is
>>> not something you can change later.
>>>
>>> -EbF
>>>
>>> On Mon, May 6, 2024 at 7:07 AM Amar Aryan via Mesa-users <
>>> mesa-users at lists.mesastar.org> wrote:
>>>
>>>> Dear MESA users,
>>>>
>>>> I am trying to evolve a subsolar (Z = Z_solar / 2 ) metallicity, 20
>>>> M_sun ZAMS star, up to the stage of the onset of core collapse by utilizing
>>>> the "20M_pre_ms_to_core_collapse" directory in the latest MESA release,
>>>> mesa-r24.03.1. By default, the directory is set for the solar metallicity
>>>> with the following controls in "inlist_mass_Z_wind_rotation":
>>>>
>>>> &star_job
>>>>    new_Z = 1.42d-2
>>>>    new_omega_div_omega_crit = 0d0
>>>>    initial_zfracs = 6 ! set to asplund 2009 abundance fractions
>>>> / ! end of star_job namelist
>>>>
>>>> &kap
>>>>    Zbase = 1.42d-2
>>>> / ! end of kap namelist
>>>>
>>>> &controls
>>>>    initial_mass = 20
>>>>    initial_z = 1.42d-2 ! ! solar
>>>>    initial_y = 0.2703d0 ! from asplund et al. 2009, solar.
>>>>    Dutch_scaling_factor = 0d0
>>>> / ! end of controls namelist
>>>>
>>>> If I set the initial metallicity to Z = Z_solar /  2, i.e., new_Z =
>>>> 0.71d-2,  Zbase = 0.71d-2, and initial_z = 0.71d-2, how should I modify the
>>>> corresponding "initial_zfracs" and "initial_y"?
>>>>
>>>> I noticed that there were no explicit options of "initial_zfracs" and
>>>> "initial_y" in "inlist_mass_Z_wind_rotation" in earlier versions of MESA
>>>> (e.g., in mesa-r23.05.1).  How is "intial_zfracs" different
>>>> than "initial_z"? Please suggest.
>>>>
>>>> With regards,
>>>> Amar
>>>> _______________________________________________
>>>> mesa-users at lists.mesastar.org
>>>>
>>>> https://urldefense.com/v3/__https://lists.mesastar.org/mailman/listinfo/mesa-users__;!!IKRxdwAv5BmarQ!etPLZ2NqREX9P3DqpN4pYzvDn4q5bXOY7MpZwKeShRNbwtT4vPB2rrSf0pcEtyjAndF8o22ATahSVRXwIjHGkMAlKXgSXQ$
>>>>
>>>>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.mesastar.org/pipermail/mesa-users/attachments/20240508/9e2f65e0/attachment.htm>