[mesa-users] create He stars by create_zams

Bill Paxton paxton at kitp.ucsb.edu
Wed May 25 12:21:44 EDT 2016


On May 25, 2016, at 3:46 AM, Ying Qin wrote:

> Dear Bill,
> 
> Based on your suggestion, I can add more grids to create a He star with different metallicities.
> I am now thinking how to allocate the fraction of the metals with respect to a specific metallicity.


If you want to use one of the pre-supplied z fractions, you do it easily by doing a 2nd step.
Save the pure helium model you have made.
Load it as starting model in a new inlist.  In the new inlist, set the desired composition

      set_uniform_initial_composition = .true.
      initial_h1 = 0 	! set mass fractions
      initial_h2 = 0
      initial_he3 = ...
      initial_he4 = ...
      initial_zfracs = 3 ! GS98  --- see star_job.defaults for other options

b







> 
> Thank you again.
> 
> Cheers,
> Ying
>> On 24 May 2016, at 23:20, Ying Qin <Ying.Qin at unige.ch> wrote:
>> 
>> Dear Bill,
>> 
>> Thank you for your quick reply.
>> I will try the method and let you know what happens.
>> 
>> Cheers,
>> Ying
>> 
>>> On 24 May 2016, at 23:11, Bill Paxton <paxton at kitp.ucsb.edu> wrote:
>>> 
>>> Hi,
>>> 
>>> create_zams is the wrong tool for the job.   
>>> 
>>> if you are aiming for much larger masses, i suggest taking a look at the test case make_massive_with_uniform_composition.
>>> you can set the target composition by editing the inlist.  it creates a C/O mix currently with these parameters.
>>> 
>>>          ! C/O MIX
>>>          ! set target uniform composition for relax_initial_to_xaccrete
>>>          num_accretion_species = 2
>>>          accretion_species_id(1) = 'c12'
>>>          accretion_species_xa(1) = 0.1582d0
>>>          accretion_species_id(2) = 'o16'
>>>          accretion_species_xa(2) = 0.8418d0
>>> 
>>> For pure He4, you'd change this to
>>>          ! He4
>>>          ! set target uniform composition for relax_initial_to_xaccrete
>>>          num_accretion_species = 1
>>>          accretion_species_id(1) = 'he4'
>>>          accretion_species_xa(1) = 1d0
>>> 
>>> set initial_mass to whatever you want.
>>> 
>>> Give it a try -- you'll be the 1st person to try this as far as I know, so let us know what happens.
>>> 
>>> Bill
>>> 
>>> 
>>> 
>>> 
>>> 
>>> On May 24, 2016, at 1:52 PM, Ying Qin wrote:
>>> 
>>>> Hi there,
>>>> 
>>>> By default, we can evolve a helium star directly by calling a model zams_z2m2_y98.data , which can create a mass range from 3.25 - 18.25 Msun.
>>>> However, I am trying to create a much larger mass range of helium star by using create_zams. Unfortunately, mesa can only create
>>>> the mass range of  ~3 - ~20Msun, and it failed due to ’stopping because of convergence problems — too many retries’.
>>>> Could any users have this similar problem or help me out ? Any comments are welcome, thank you in advance.
>>>> 
>>>> BTW, I am using mesa-r8118 with the latest mesasdk. Inlist and the unsuccessful z2m2_y98.data are attached below.
>>>> 
>>>> Cheers,
>>>> Ying
>>>> <inlist_zams_specification>
>>>> <z2m2_y98.data>
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>> 
>> ------------------------------------------------------------------------------
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>> restrictions. Mobile Device Manager Plus allows you to control only the
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> 

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