[Mesa-users] Question about neon burning rates

[Ebraheem Farag]

Hi Jeremy,

I think...
Carbon burning occurs beyond 0.6 GK.
An a-channel product for carbon burning is: c12+c12 -> 24mg* ->  20ne +
alpha.
These alphas can power the forward rate 16o(alpha,gamma)20ne (faster) and
20ne(alpha,gamma)24mg (slower). This is one reason why the total o16
abundance decreases slightly during C burning, and ne20 and mg24
accumulate.

Then near 1.5 - 1.6 GK the reverse rate 20ne(gamma,alpha)16o becomes
important and ne20 "melting" or photodisintegration rearrangement takes
over as 2(ne20) -> 16o + mg24 + gamma, followed by O burning.


-EbF


On Tue, Dec 5, 2023 at 2:56 PM Jeremy Sakstein <sakstein at hawaii.edu> wrote:

> Hi Ebraheem,
>
> I am using approx21 but what you said is surprising. I would not expect
> 20Ne(alpha,gamma)24Mg to be important at the temperatures of my model
> (logT~8.6-8.8).
>
> Cheers,
>
> Jeremy
>
> On Tue, Dec 5, 2023 at 11:41 AM Ebraheem Farag <ekfarag at asu.edu> wrote:
>
>> If you're using an approx21 network, the "burn_ne" label refers
>> exclusively to 20Ne(alpha,gamma)24Mg. Otherwise, it is an umbrella term as
>> Frank described.
>>
>> -EbF
>>
>> On Mon, Dec 4, 2023 at 11:12 PM Jeremy Sakstein via Mesa-users <
>> mesa-users at lists.mesastar.org> wrote:
>>
>>> Hi everyone,
>>>
>>> I am interested in tracking neon burning, and have arrived at a bit of a
>>> puzzle.
>>>
>>> I am seeing significant neon burning via the 'burn_ne' profile variable
>>> at temperatures of order logT=8.6-8.8 i.e., lower than I would expect neon
>>> burning to be significant. I am working with version 12778.
>>>
>>> When I look at rates/private/ratelib.f90, I can see that the ne20gp
>>> reaction redirects me to f19(p,g)ne20. When I look up this rate, it appears
>>> that it is important at the temperatures I am working with, so could be
>>> responsible for the neon burning I am seeing. My current hypothesis is that
>>> I am seeing the inverse reaction happening.
>>>
>>> Does anyone have any insight into this?
>>>
>>> Also, can someone tell me why the rne20gp redirects me to f19(p,g)ne20?
>>>
>>> Cheers,
>>>
>>> Jeremy
>>>
>>> --
>>> Jeremy Sakstein (He/Him/His)
>>> Assistant Professor of Theoretical Physics
>>> Department of Physics & Astronomy
>>> University of Hawaiʻi at Mānoa
>>> Watanabe Hall
>>> 2505 Correa Road
>>> Honolulu, HI, 96822, USA
>>> http://www.jeremysakstein.com
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>
> --
> Jeremy Sakstein (He/Him/His)
> Assistant Professor of Theoretical Physics
> Department of Physics & Astronomy
> University of Hawaiʻi at Mānoa
> Watanabe Hall
> 2505 Correa Road
> Honolulu, HI, 96822, USA
> http://www.jeremysakstein.com
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