[mesa-users] mesa release 4631 -- revise interface for Type2 opacities (again)

Bill Paxton paxton at kitp.ucsb.edu
Sat Oct 27 00:01:39 EDT 2012


one more try on Type2 opacities.  this time maybe we've got it.
to remind you why the changes are happening, in the old days you had to pick
one or the other, Type1 or Type2, for all cells in the model.
for many applications that was okay.  but not all.
in particular if you have a metal poor envelope (from gravitational settling, say)
and a metal rich core, you might need Type2 in the core and Type1 in the envelope
(recall that Type2 tables don't go to X > 0.7 while the Type1 tables go up to pure H).

that's the motivation.  we've been flailing around a bit looking for a solution.
my first try was elegant (at least to one computer scientist) but had the downside
of being basically garbage physically (as Falk tenderly pointed out to me!)
so, try again.  now you can set a range of X (say 0.69 to 0.71) over which the
code automatically blends from Type2 to Type1.  if you don't want to blend,
just set the range to > 1.  also you can either let the code calculate the base
metallicity for Type2 or you can explicitly give a value like in the old days.

about the only other thing that is changed in this release is the smoothing
for the brunt_B composition term; it now uses the local pressure scale height
as a unit for determining the width of the top hat smoothing function.

oh, and there is an option suggested by Falk to set logT limits for opacity_factor
so it can be used to reduce the iron bump. (thank you Falk!)

and Pablo Marchant has contributed improvements to the star/binary_systems code.
(thank you Pablo!)

and there have been some changes in the astero_adipls controls as suggested
by Dennis Stello (thank you Dennis!)


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