[mesa-users] type 2 opacities

[Radek Smolec]

Hi Bill,

>        real(dp) :: kap_type2_logT_lower_bdy = 3.8d0
>>       ! below this, turn off type2
>>
> A comment on the default values. Of course it is the MESA-user job to
> check whether the default values will work for his/her problem, but
> logT=3.8 is very low. Taking into account its priority with respect to
> X-controls, the type 2 opacities once turned on are in fact used in all
> zones, maybe except the thin atmospheric layers of cool stars, during full
> evolution, also MS or even PMS, when no significant enhancement in C/O is
> expected. Indeed, the MS tracks computed with type 2 opacities differ from
> those computed with type I opacities (assuming default values for X/T
> transitions). The differences are likely caused by larger interpolation
> gaps in type 2 opacities (interpolation is less accurate), but also in my
> specific case, by different solar mixtures. With the default logT
> transition to Type 2 we actually use gn93 mix in all the star, independent
> of what was set for Type 1 mix (with kappa_file_prefix, gs98 in my case).
>
>
> I'm confused here --- what do you think the default should be?   Or do you
> think this control shouldn't exist?   Or what?   Keep in mind the cases
> with C/O rich material near the surface.
>
OK, I am too much confined to evolution only up to helium depletion in the
core. For these phases logT should be larger I think (and X controls
lower), so we use Type 2 only where we really should. But as you pointed
out for other applications lower value might be a better choice.
Radek
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