[mesa-users] Tricks to create CO white dwarfs

[Pablo Marchant]

Thanks Aaron. It seems that lowering the opacity to kill the iron bump is
pretty effective. For my purposes, this is more than enough.

On Sat, May 16, 2015 at 11:22 PM, Aaron Dotter <aaron.dotter at gmail.com>
wrote:

> Hi Pablo,
>
> This is not a solver adjustment, but I've had good results from limiting
> the Fe-bump opacity.  This works nicely if you plot the opacity profile in
> the slow part of your evolution and then adjust these factors to smooth
> that profile for logT < 6.  This is definitely stellar engineering, not
> stellar physics!
>
> Aaron
>
>          !### opacity_max
>
>          ! limit opacities to this value (ignore this is value is < 0)
>
>       opacity_max = -1
>
>
>          !### opacity_factor
>
>          ! opacities are multiplied by this value
>
>       opacity_factor = 1
>
>
>          !### min_logT_for_opacity_factor_off
>          !### min_logT_for_opacity_factor_on  and
>          !### max_logT_for_opacity_factor_on
>          !### max_logT_for_opacity_factor_off
>
>          ! temperature controls for where the `opacity_factor` is applied
>          ! if, for example, you only want the opacity factor to apply in the iron bump region
>          ! you can give a logT range such as
>
>          !     min_logT_for_opacity_factor_off = 5.2
>          !     min_logT_for_opacity_factor_on = 5.3
>          !     max_logT_for_opacity_factor_on = 5.7
>          !     max_logT_for_opacity_factor_off = 5.8
>
>          ! ignore these if < 0.
>
>       min_logT_for_opacity_factor_off = -1
>       min_logT_for_opacity_factor_on = -1
>       max_logT_for_opacity_factor_on = -1
>       max_logT_for_opacity_factor_off = -1
>
>
>          ! if you need cell-by-cell control of opacity factor,
>          ! set the vector "`extra_opacity_factor`" using the routine "`other_opacity_factor`"
>
>
>
> On Sun, May 17, 2015 at 1:22 AM, Pablo Marchant <pamarca at gmail.com> wrote:
>
>> Pgas/P ~ 0.2 at its minimum. I am precisely looking for these
>> "engineering tricks", and whether or not others have found successful ways
>> to do this in other, less tricky ways. Something like playing with the
>> solver tolerances in just the right way to boost a bit performance.
>>
>> On Sat, May 16, 2015 at 1:03 PM, Aaron Dotter <aaron.dotter at gmail.com>
>> wrote:
>>
>>> Hi Pablo,
>>>
>>> What are the initial and current masses of the stars when you have
>>> convergence issues?
>>>
>>> Do you find regions in these stars where Pgas/P << 1?
>>>
>>> If you're experiencing this sort of problem, there are a few
>>> "engineering" tricks, like limiting max opacity or MLT++, that will get you
>>> through faster.  Otherwise you need patience.
>>>
>>> Aaron
>>>
>>>
>>> On Saturday, May 16, 2015, Pablo Marchant <pamarca at gmail.com> wrote:
>>>
>>>> Hi all. For the last days I've been playing with some systems that will
>>>> end their lives as CO white dwarfs, but I always run into convergence
>>>> problems close to stripping the CO core. At that point maybe it manages to
>>>> go through after several hundred thousand steps, but that makes it a bit
>>>> unpractical if I want to model several. So I was wondering if others with
>>>> experience on the topic could share their tricks to get through this phase.
>>>>
>>>> I know the test_suite case make_co_wd makes use of MLT++, so in
>>>> particular I'm looking to find if others have managed to get things to work
>>>> with plain old MLT.
>>>>
>>>> Cheers!
>>>>
>>>> --
>>>> Pablo Marchant Campos
>>>> M.Sc on Astrophysics, Universidad Católica de Chile
>>>> PhD student, Argelander-Institut für Astronomie
>>>>
>>>
>>
>>
>> --
>> Pablo Marchant Campos
>> M.Sc on Astrophysics, Universidad Católica de Chile
>> PhD student, Argelander-Institut für Astronomie
>>
>
>


-- 
Pablo Marchant Campos
M.Sc on Astrophysics, Universidad Católica de Chile
PhD student, Argelander-Institut für Astronomie
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