[Mesa-users] Finding ZAMS

[Thomas Steindl]

Hello,

I am working on pre-MS Asteroseismology. Therefore, I am calculating  
MESA models which I use as input for GYRE. In my analysis, I need to  
know the timestep at which the star reaches ZAMS. Unfortunately, I  
fear the stopping conditions implemented in MESA do not work. To show  
this I have used three different inlists. A first, very simple inlist  
(Basic_inlist), an inlist with additional varcontrol  
(additional_varcontrol) and one with additional varcontrol and using  
the ppandcnoextras net instead of the basic net  
(additional_varcontrol_and_net). I have also attached the  
corresponding inlists. In the corresponding png files, I have plotted  
the values for log_L and log_Lnuc in the upper panel and the ratio  
L/Lnuc in the lower panel. As you can see, the ratio seems to converge  
to the value 1 for the first two inlists (for which this stopping  
criterion works). But for the latter of the three inlists, Lnuc  
exceeds L at some point in the evolution and the stopping criterion  
fails.

The zip folder 'ZAMS_second_stop_option' contains plots for 30 stellar  
models computed with the 'additional_varcontrol_and_net' inlist and  
different masses. In the 30 pngs in this folder I have plotted log_L  
and log_Lnuc in the upper pannel and  
abs(log(power_hburn)-log_surface_luminosity) in the lower panel. The  
title shows the mass of a specific model and the value of  
L_nuc_counter which states how many timesteps Lnuc/L has been between  
0.99 and 1.01. As you can see, the value for the second stop option  
exhibits drops (mostly while log_Lnuc > log_L) which in terms makes  
this stop option unreliable and I don't see how it can function as  
global stop option for all masses.

I have tried other options (gravitational energy, contraction speed,  
etc.), yet I cannot find a criterion. Do you have any idea on which  
stellar properties I could use? Any help would be greatly appreciated.

Thank you in advance,
Thomas Steindl

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