[mesa-users] energy generation and reaction rates

[Bill Paxton]

Thanks for the input Dave.

For those brave souls who'd like to dig deeper, here's a way to get mesa/star to give you some information about a specific cell.
You can then use the information about T, Rho, and abundances from star to set up more tests in mesa/net to get yet more details.

In mesa/star/private/net.f, edit this to have the cell (k) and the model_number and perhaps even the newton iter that you want to look at.

         if (k == 3123 .and. s% model_number == 2001 .and. s% newton_iter == 1) then
         !if (.false.) then
            write(*,*)
            call show_stuff(s,k,net_lwork,net_work)
            write(*,1) 's% eps_nuc(k)', s% eps_nuc(k)
            write(*,1) 's% d_epsnuc_dlnd(k)', s% d_epsnuc_dlnd(k)
            write(*,1) 's% d_epsnuc_dlnT(k)', s% d_epsnuc_dlnT(k)
            write(*,*)
            write(*,*) 'do1_net'
            stop
            !ierr = -1
         end if

Then when you remake and rerun, you get something like this on the terminal:
it has raw and screened rates for each reaction as well as dt*dxdt for each iso.

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At the end of the output you'll find some lines that you can cut-and-paster into the net/test/src test file.
                                   xin(net_iso(ihe4))=     9.1864805040892039D-01
                                    xin(net_iso(ih1))=     6.7672331857974971D-02
                                   xin(net_iso(in14))=     8.4732356427420167D-03
                                  xin(net_iso(img24))=     3.4800293512379072D-03
                                  xin(net_iso(ine20))=     1.3156800181077129D-03
                                   xin(net_iso(io16))=     2.9372549445265617D-04
                                   xin(net_iso(ic12))=     1.1694710948875307D-04
                                   xin(net_iso(ihe3))=     1.1707547245030843D-10

                                                    T =    3.0682780872719310D+07
                                                 logT =    7.4868947184759556D+00
                                                  rho =    8.4070337003162710D+00
                                               logRho =    9.2464278832736402D-01
                                                 abar =    3.3536962584707743D+00
                                                 zbar =    1.7903243523778676D+00
                                                z2bar =    3.5044818854138851D+00
                                                   ye =    5.3383616594849992D-01
                                                  eta =   -5.7272317069384631D+00
 screening_mode = extended
                                              theta_e =    0.0000000000000000D+00


You can take a look at subroutine show_stuff in star/private/net to see about adding more output.
However, as has been mentioned, the energy generation from a particular reaction is not one of the options.
But given screened rates and Q values, you can take care of that yourself.

Good luck,
Bill








On Feb 27, 2015, at 11:42 AM, David Arnett wrote:

> For simple, single reaction links there is a one-to-one correspondence; as Frank said, use \Delta E=\Delta m \times c^2.
> For a more complex reaction network  it is not so simple. The energy generation may now depend upon multiple reactions; energy generation is an ensemble average. To get the contribution from each link can be done, but as Frank says, that is "black belt" level. Note that for each link the contribution may depend upon what other links are doing, so disentangling them can be very messy.
> 
> --
> David Arnett
> Regents Professor
> Steward Observatory
> University of Arizona
> 
> Facts are stubborn, but statistics are more pliable.  Mark Twain
> Facts do not cease to exist because they are ignored.  Aldous Huxley
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