[Mesa-users] An error in extras file for branching ratios of pp2 and pp3

[Steindl, Thomas]

Hello again,

the run_star_extras i attached gives log_eps_nuc for the three branches in the basic net (r_he3_he3_to_h1_h1_he4, r34_pp2, and  r34_pp3). You can not just compare the profile output of pp with any of  the three as pp also involves other reactions (see http://cococubed.asu.edu/code_pages/burn_hydrogen.shtml ).
But we can use the output of the three branches, integrate over the star and then calculate the ratios. With a quick model I found pp1 84.078%, pp2 15.903% and pp3 0.019%.  This rates compare not to bad for pp1 and pp2 (see again http://cococubed.asu.edu/code_pages/burn_hydrogen.shtml ). Adelberger et al ( https://journals.aps.org/rmp/abstract/10.1103/RevModPhys.83.195 ) give 83.3% for pp1 and 16.7% for pp2 and pp3 which splits in 99.88% and 0.12% , giving a total of pp1 83.3% pp2  16.68%  and pp3 0.02% which is close to the values I found. I have no idea where the difference for the pp3 branch of this two comparisons arises from.

Now we have to keep in mind that we are using the basic.net which handles the pp2 and pp3 chains as one reaction instead of 3 and 4. Using the net pp_extras.net would give us more detail in the calculation of the pp chain. One would have to include more reactions in the run_star_extras file but this should be straightforward.

Additionally, this run_star extras gives the branching ratios as history output called branch_ratio_pp1, etc. computed in the way I described above. This would of course also need updating if you decide to go for a more detailed net. I hope this helps.

Thomas
________________________________
From: Mesa-users [mesa-users-bounces at lists.mesastar.org] on behalf of Jaime Montes Norniella via Mesa-users [mesa-users at lists.mesastar.org]
Sent: Thursday, January 23, 2020 11:03 PM
To: mesa-users at lists.mesastar.org
Subject: [Mesa-users] An error in extras file for branching ratios of pp2 and pp3

The last run.extras.f for the branching ratios of pp chain was a minor mistake:
The profile returns the log of eps_nuc  of pp2 and pp3 but the names of the new columns are eps_nuc. of  pp2 and pp3
The bug is corrected in this new file.

A big question is:
The values returned for a 1 solar mass star  and solar luminosity in mean sequence for log_eps_nuc of pp2 and pp3 are very high compared with the values returned in log10 of the ‘pp’ variable. Why?

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