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

[Francis Timmes]

many of your questions could be answered by 
you studying the source code. have you looked?

fxt





> On Feb 11, 2016, at 6:10 PM, Ian Foley <ifoley2008 at gmail.com> wrote:
> 
> 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
> 
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