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

[Bill Paxton]

Hi Josh,

That all sounds right.

Good luck!

-Bill



On Oct 29, 2012, at 6:34 PM, Josh Shiode wrote:

> 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?
> 
> Thanks,
> Josh
> 
> 
>> Hello,
>> 
>> 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!)
>> 
>> Cheers,
>> Bill
>> 
>> 
> 
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