[Mesa-users] Questions regarding PISN

[Francis Timmes]

hi ealeal,

on 1, remnant_mass_min_limit is similar to deciding how close to zero is good enough.
for say a 200 msun initial he core mass, 180 msun has already reached scape speed with only 20 msun remaining. 
for a test suite case, this is a good enough approximation to the entire mass being unbound.
explore changing the inlist settings, especially if one building upon a test suite case for a science project.

on 2, all three stopping conditions are different ways of detecting when the model is 
gravitationally unbound or undergoing core-collapse. whether the different stopping conditions 
yield meaningful science differences is an exploration exercise.

on 3, https://docs.mesastar.org/en/release-r22.05.1/reference/star_job.html#required-termination-code-string

required_termination_code_string(:) = '' 

the fortran (:) part allows one to set specific positions within the character string. for example,
to set the 6th and 7th characters to "a" and "b" respectively, required_termination_code_string(6:7) = 'ab'. 
most use cases simply set the character string.

on 4, its just a different number, a different part of parameter space.
feel free to explore the impact of changing inlist settings.
mesa is a tool, not a model ...

fxt






> On Sep 17, 2022, at 10:56 PM, Bear Ealeal via Mesa-users <mesa-users at lists.mesastar.org> wrote:
> 
> Dear MESA users,
> 
> I am trying to understand the example of PISN in MESA 22.05.1.
> 
> In test suite: When the routine finished in the last inlist of inlist_finish there are three physical stopping conditions:
> 
> log_Rsurf_upper_limit = 5d0
> 
>       fe_core_infall_limit = 2.5d7
> 
>       remnant_mass_min_limit = 20d0 ! stop here for completely unbound cases.
> 
> I have a few questions:
> 
> 1.      I am not sure I follow the logic, PISN should leave no remnant, but the conditions refer to a remnant. How does it work? Does the code assumes that at this point we can not continue numerically and a PISN is unavoidable?
> 
> 2.      Also is there a difference in the final outcome between the conditions ? so far I only received this one” remnant_mass_min_limit” and then I get “star is unbound” , I run a few runs around 200Mo so far up to 170Mo, so the terminal writes “star is unbound”.
> 
> 3.      I am not sure I understand the number of “required_termination_code_string(number)”, how does this number work, I could not find something that connects it to the stopping condition. I only found in do_one_utils.f90 the output of the terminal, so I am guessing it only applies to added termination strings and not to existing ones? is this true or did I miss something?
> 4.      I tried looking at another example in test_suite: a CCSN for comparison: the stopping condition  there is   fe_core_infall_limit = 1d7, which is lower than PISN, here there is remnant so I understand the stopping condition but why is the number lower than PISN?
> 
> Thanks in advance for all your help,
> 
> Ealeal
> 
> 
> 
> 
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