[mesa-users] mesa release 4631 -- revise interface for Type2 opacities (again)
jhshiode at berkeley.edu
Mon Oct 29 21:34:25 EDT 2012
Hi Bill et al.,
So if I want to evolve beyond He burning in a massive star, I would want type2 opacities there, but keep type1 in the envelope/outer core. So in this case, should I simply set use_type2_opacities = .true., and then the default
kap_Type2_full_off_X = 0.71d0
kap_Type2_full_on_X = 0.69d0
will blend the tables for the high H envelope composition?
In the core, will the local values of C and O be used to determine the correct opacity tables for a given cell?
Lastly, I see that there are only gn93 mixture type2 tables, this means that I would need to use that mixture everywhere (by setting kappa_file_prefix = 'gn93'), right?
> 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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