[Mesa-users] Thank you and questions

[Francis Timmes]

hi piet,

for now, i'll address 6.

in fortran one can define a "structure", like this

type fruit
 real diameter
 real length
 character color
end type fruit

one can then declare two "fruit" variables, like this

type(fruit) apple, banana

and assign values to these variables, like this

apple   = fruit(50,45,"red")
banana  = fruit(40,200,"yellow")

one then calculates with them like this

area_apple    = apple%diameter * apple%length
volume_banana = 3.14 * banana%diameter * banana%diameter * banana%length

in mesa, the structure is "star" and type is "s", so
s%mass, s%radius, and so on.

clearer?

fxt






> On Oct 11, 2018, at 9:57 PM, Piet Martens via Mesa-users <mesa-users at lists.mesastar.org> wrote:
> 
> Dear all,
> 
> First a big "Thank You" to everyone who put MESA together and is maintaining
> it!  I don't program or run big codes, so I was apprehensive, but it turned
> out that everything worked as described in the directions, and the directions
> were unambiguous. What a difference with, say, upgrading from MacOs El Capitan
> to Sierra, which took me a long frustrating weekend.
> 
> It is indeed also a lot of fun to follow a star as it is evolving, and amazing
> to see how fast the run goes.  My project is looking at solar evolution under
> different mass loss scenarios related to the Faint Young Sun Paradox.
> 
> Here are my questions, and forgive me if they seem amateurish:
> 
> 1. I use the Asplund09 metal fractions, both for initial_zfracs and
>    kappa_file_prefix.  I take it the first sets the initial conditions and
>    the second is for calculating the (initial?) opacities.  So could one, to
>    create an absurd scenario, use Asplund09 for one and, say, GS98 for the
>    other?
> 2. Related to that, it is not clear to me what elements (as well as isotopes
>    and ionization states) are evolved and used for opacity calculations by
>    MESA.
> 3. Again related to that, I do not quite understand the function of "net".
>    (If you can point me to a good online source to explain, that would save
>    you the time needed for a long response).
> 4. I take it that opacity_factor simply multiplies all calculated opacities
>    by that factor?  That to get around by the difference in metallicity
>    derived from spectroscopy and that indicated by helioseismology?  (It
>    worked for me to reconcile the observed metal fractions with T_eff and
>    R_sun for one solar mass, once element diffusion is switched on as well).
>    Is it possible to tinker with the opacity_factor for individual elements?
> 5. v_div_cs is the convective velocity as a fraction of the sound speed at
>    the surface cell, correct?  Is that an observable, say by line broadening
>    in stars, or Doppler shifts and tracking on the Sun?  Curiously I find
>    that that parameter is quite sensitive to the mass loss history.  I do
>    not understand why, but if this is confirmed upon multiple checks,
>    perhaps it could be a diagnostic.  Am I missing an obvious physical
>    explanation?
> 6. I sort of get the idea of "s%", but can you give me the exact definition?
> 7. This is a comment, not a question.  I was confused initially by the line
>    "wind_scheme = ''".  I left the space between single quotes empty, as I
>    thought was indicated, but that led to an error message.  One really has
>    to comment out that line to make it work.  Not totally clear (for me).
> 8. Upon compiling many error messages appear of the sort "ld: warning: object
>    file (/Applications/mesasdk/lib/libhdf5_fortran.a(H5_ff.o)) was built for
>    newer OSX version (10.13) than being linked (10.12)".  That is meant to
>    say to use High Sierra instead of Sierra, I think.  Do you know if that
>    leads to errors?  Doesn't seem so, as MESA works fine on Sierra for me.
>    (I'd rather not upgrade my MacOs again....).
> 
> Thanks again!
> 
> -- 
> Piet Martens, Dept. of Physics & Astronomy
> Georgia State University
> 25 Park Place, 6th Floor, Room 624
> Atlanta, GA 30303
> Office Phone:  404-413-6612
> Dept. Fax:  404-413-5481
> 
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