[Mesa-users] Thank you and questions

[Piet Martens]

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