[mesa-users] TP-AGB and Post-AGB Mass Loss Issues

[Ian Foley]

As part of my personal education of Stellar Evolution, I have been
running the 1M pre ms to wd test suite case up to 9M and trying out
and learning about the inlist.

The big issue I see is to understand how mass loss is applied and its
relationship to the thermal pulses.

Very evident is that if I increase the RGB and AGB scaling factors ( I
have tried from 0.1 up to 8) it flattens out and reduces the number of
thermal pules I suspect this is because as we increase the mass loss
via the mass loss formulae, the larger and more frequent TP's are not
needed to remove the mass.

This has led me to try to find answers to the following questions.

1. Is the mass loss formula applied to every zone to compute the loss?
If yes, why isn't mass loss calculated by using the radial velocity
and computing the amount of matter expelled through the star's outer
zone. If no, how is the formula applied?

2. Is the mass loss formula applied only to H? Or is it applied to He
and others as well?

3. I have been primarily using the Reimer and Blocker mass loss
formula which is I think a heuristic formula determined by
experimental observations. However, it does seem to be applied fairly
independently of the actual stellar evolution equations. Since we
don't know very well from experiment the number and scale of the TP's
how can we know what is a good scaling factor to use.

4. In relation to the new solar wind additions in r8118 over r7624
it's not quite clear to me what is the relation between the Reimer and
Blocker terms and turning on and off the the cool wind dependent on
temperature. Are the Reimer and Blocker factors still needed and the
cool wind temperature terms just configure when they are activated?

5. I have similar issues with the convection overshooting. Although it
seems likely to be important it seems we have no idea of the
appropriate number to apply. And, like mass loss, the bigger the
factors you choose the more it dampens the TP's.

6. How is the mass loss formula's applied in the post-AGB phase? Does
the Blocker term just switch off at some point and if so when? Why
does it seem that there is no He loss in the post-AGB phase?

7. I find it very strange that in the post-AGB phase the lg_LH term in
the terminal output is still up close to the total lg_L even when
there is almost no hydrogen left and what hydrogen there is in the
outer zones of the envelope.

       step    lg_Tcntr    Teff       lg_LH     lg_Lnuc     Mass
H_rich
H_cntr     N_cntr     Y_surf     X_avg     eta_cntr  zones retry
   lg_dt_yr    lg_Dcntr    lg_R       lg_L3a    lg_Lneu     lg_Mdot
He_core    He_cntr    O_cntr     Z_surf     Y_avg     gam_cntr  iters
bckup
     age_yr    lg_Pcntr    lg_L       lg_LZ     lg_Psurf    lg_Dsurf
C_core
C_cntr     Ne_cntr    Z_cntr     Z_avg     v_div_cs     dt_limit

      39400   8.211499  2.889E+04   4.255626   4.354482   0.985786
0.000116   0.000000   0.000000   0.374091   0.000065  49.353686   2183
  5037
  -5.801543   7.277248   0.753659   3.545685   3.889458  -4.012795
0.985670   0.000000   0.579524   0.020125   0.001666   7.754729      6
    31
 3.5571E+07  24.321104   4.303656   3.038122   3.281056 -10.342147
0.982096   0.394597   0.001949  1.000E+00  9.983E-01  0.000E+00
varcontrol

Is this OK or is there a problem with the software?


I would be very grateful for any help in answer to these questions
Ian