[Mesa-users] Question about nuclear reaction rates

[Francis Timmes]

please keep all replies on mesa-users.


just follow the units:

energy/time = energy/reaction * reaction/time

4e33 erg/sec ~ 4.2e-5 erg/reaction * reaction/sec

so, 

reaction/sec ~ 4e33/4.2e-5 ~ 1e38

fxt




> On Jul 17, 2023, at 11:28 PM, 王浩 <wangfeihao at stu.xju.edu.cn> wrote:
> 
> Dear Francis Timmes,
> 
> Thank you very much for your explanation. But I don't know what to make of 4e33/4e-5 on the last line. Why divide the sun's luminosity by 4e-5.
> 
> Best wishes,
> Wang Hao
> 
> 
>> -----原始邮件-----
>> 发件人: "Francis Timmes" <fxt44 at mac.com>
>> 发送时间: 2023-07-17 22:55:27 (星期一)
>> 收件人: "王浩" <wangfeihao at stu.xju.edu.cn>
>> 抄送: "Frank Timmes" <fxt44 at mac.com>, mesa-users <mesa-users at lists.mesastar.org>
>> 主题: Re: [Mesa-users] Question about nuclear reaction rates
>> 
>> to polish this off from my side,
>> 
>> pp I energetics:
>> 
>> p + p -> d + e^+ + nu
>> 
>> the positron annihilates, so 
>> 
>> p + p -> d + nu + 1.442 MeV
>> 
>> d + p -> he3 + gamma + 5.493 MeV
>> 
>> he3 + he3 -> he4 + 2p + 12.732 MeV
>> 
>> so the net is 4p -> he4 + 26.1 MeV, accounting for the ~0.6 MeV lost to neutrinos.
>> 
>> 26.1 MeV ~ 4.2e-5 erg, so the number of pp I reactions per second to sustain Lsun is ~4e33/4e-5 ~ 1e38 reactions/sec, which is commensurate with fig 25 of mesa VI.
>> 
>> fxt
>> 
>> 
>> 
>>> On Jul 17, 2023, at 5:49 AM, 王浩 <wangfeihao at stu.xju.edu.cn> wrote:
>>> 
>>> Dear Francis Timmes,
>>> 
>>> Thank you sincerely for recommending those books to me. They have proven to be incredibly helpful.
>>> 
>>> Best wishes,
>>> Wang Hao
>> 
>> 
>> 
>> 
>>> 
>>>> -----原始邮件-----
>>>> 发件人: "Francis Timmes" <fxt44 at mac.com>
>>>> 发送时间: 2023-07-16 23:31:20 (星期日)
>>>> 收件人: "王浩" <wangfeihao at stu.xju.edu.cn>
>>>> 抄送: "Frank Timmes" <fxt44 at mac.com>, mesa-users <mesa-users at lists.mesastar.org>
>>>> 主题: Re: [Mesa-users] Question about nuclear reaction rates
>>>> 
>>>>> Meanwhile, I would like to understand the definition of the nuclear reaction rates within a star and its units.
>>>> 
>>>> amongst several textbooks, "nuclear physics of stars" second edition by christiam iliadis or "essentials of nucleosynthesis and theoretical nuclear astrophysics" by thomas rauscher.
>>>> 
>>>> fxt
>>>> 
>>>> 
>>>> 
>>>> 
>>>>> On Jul 16, 2023, at 3:02 AM, Earl Bellinger via Mesa-users <mesa-users at lists.mesastar.org> wrote:
>>>>> 
>>>>> Dear Wang Hao, 
>>>>> 
>>>>> Many thanks for your email. The inlists and code to generate Figure 25 are included in the following MESA Zenodo repository: 
>>>>>   https://zenodo.org/record/6968760 
>>>>> I have just run it with mesa-r22.05.1 and found that I get similar results as what was presented in the paper. 
>>>>> 
>>>>> If you can point to some discrepancies then I would be happy to take a further look. 
>>>>> 
>>>>> Best wishes, 
>>>>> Earl 
>>>>> 
>>>>> Earl Patrick Bellinger Postdoctoral Research Fellow
>>>>> Max Planck Institute for Astrophysicshttps://earlbellinger.com 
>>>>> 
>>>>> On Sun, Jul 16, 2023 at 5:40 AM 王浩 <wangfeihao at stu.xju.edu.cn> wrote:
>>>>> Hi, everyone,
>>>>> 
>>>>> I’m very interested in using mesa-r22.05.1 to obtain nuclear reaction rates. However, I have encountered a particular issue. When I output the nuclear reaction rate of a 1M⊙ model using mesa-r22.05.1, the magnitude of the rates I obtain is significantly smaller than what is depicted in Figure 25 of paper titled “Modules for Experiments in Stellar Astrophysics (MESA): Time-Dependent Convection, Energy Conservation, Automatic Differentiation, and Infrastructure,” which was published in the APJS. I wonder why that is. Meanwhile, I would like to understand the definition of the nuclear reaction rates within a star and its units.
>>>>> 
>>>>> Best regards, 
>>>>> Wang Hao
>>>>> _______________________________________________
>>>>> mesa-users at lists.mesastar.org
>>>>> https://lists.mesastar.org/mailman/listinfo/mesa-users
>>>>> 
>>>>> _______________________________________________
>>>>> mesa-users at lists.mesastar.org
>>>>> https://lists.mesastar.org/mailman/listinfo/mesa-users
>>>>> 

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