[Mesa-users] about the decay rates of al26, al26-1 and al26-2

[Francis Timmes]

hi er-tao,

new public release 10398 can do the al26 isomers.
as verification, attached is a take on figure 5 of ward & fowler 1980.
the equilibration timescales for the chosen initial conditions and the 
analytical thermal equilibrium values for of al26-1 <-> al26-2  are matched.
see the release notes for how to use this new capability.


> Secondly, the partition functions in $MESA/data/chem_data/isotopes.dat should affect the decay rates of al26, al26-1 and al26-2. However, after I changed the partition functions, the decay rates do not change at all. Does MESA use the partition function?

these have always worked - see the attached plot showing the impact 
of changing the tabulated partition values by a factor of 100 on the 
reverse rate of mg25(p,g)al26-1. recall that mesa caches reaction rates
the first time a reaction is encountered, and uses that cached rate for 
future occurrences. if the partition functions are changed, then one needs 
to delete the corresponding *.bin file. by default, these cached rates 
are in data/rates_data/cache/ .

fxt





> On Feb 6, 2018, at 7:31 AM, Ertao Li via Mesa-users <mesa-users at lists.mesastar.org> wrote:
> 
> Dear all,
> 
> I am trying to do some research about the abundance of Al26 by using the MESA. I have some questions about the decay rates of al26, al26-1 and al26-2, because they confuse me. Can anyone help please?
> 
> Firstly, I noticed that the decay rates (stored in cache/*.bin) of  al26, al26-1 and al26-2 are constant and do come from $MESA/data/rates_data/JINA_reaclib***. But, from the MESA instruction paper  apj 220 (2015) 15, page 32:
> \8. WEAK REACTIONS
> \The rates module provides weak reaction rates for
> \hundreds of isotopes. By default, when atoms are fully ionized,
> \these rates are based (in order of precedence) on the tabulations
> \of Langanke & Martínez-Pinedo... 
> 
> What I think is that MESA only creates the decay rates from JINA but doesn't use them, MESA uses the  $MESA/data/rates_data/weakreactions.tables to get the decay rates but doesn't save them.  Am I correct?
> 
> Secondly, the partition functions in $MESA/data/chem_data/isotopes.dat should affect the decay rates of al26, al26-1 and al26-2. However, after I changed the partition functions, the decay rates do not change at all. Does MESA use the partition function?
> 
> Thirdly, why is the partition function of al26-1 and al26-2 always equal 1.0?
> 
> Lastly, how can I include the excitation and de_excitation between al26-1 and al26-2?
>         
> Thanks in advance,
> Ertao!
> 
> Er-Tao Li(李二涛)
> Assistant Professor                                                              Visiting Scholar
> College of Physics & Energy                                                 Konkoly Observatory
> Shenzhen University                                                             Hungarian Academy of Sciences           
> Nanhai Ave 3688, Shenzhen, Guangdong, P.R.China, 518060   H-1121 Budapest, Konkoly Thege Miklós út 15-17
> Tel: +86-755-26536232. Fax: +86-755-26534374                    Ph: +36 70 25 9 8316
> _______________________________________________
> mesa-users at lists.mesastar.org
> https://lists.mesastar.org/mailman/listinfo/mesa-users



-------------- next part --------------
A non-text attachment was scrubbed...
Name: al26-1_al26-2_equilibration.pdf
Type: application/pdf
Size: 5449 bytes
Desc: not available
URL: <https://lists.mesastar.org/pipermail/mesa-users/attachments/20180321/d73b9a18/attachment.pdf>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: partition_function_effects_on_25mg_pg_26al-1.pdf
Type: application/pdf
Size: 20507 bytes
Desc: not available
URL: <https://lists.mesastar.org/pipermail/mesa-users/attachments/20180321/d73b9a18/attachment-0001.pdf>