Re: mesa-users] Successful compilation

[Bill P. <pa...@ki...>]

Hi Marcin,

On Dec 3, 2008, at 11:43 AM, Marcin @ astrophysics wrote:

> I read mesa description at sourceforge and tried to run a model  
> even of 0.05Msun. Mesa successfully produced outcomes. May I rely  
> on them?

I think the mesa microphysics should be okay down to about 0.01Msun  
since the eos includes the SCVH data for sub-stellar objects.  So the  
low mass results are probably as good as the rest, but I can't really  
say how good that is yet -- more testing is needed to verify/validate/ 
calibrate.

>  Is it possible to expand mass boundaries? Let's say lower than  
> 0.03Msun and higher than about 120Msun.

At the low mass end, I've run some simple roche lobe overflow  
experiments that are able to reduce masses down to below 0.02.

At the high mass end, there are convergence problems with the current  
code that seem to get worse the more radiation dominated the star  
is.  It may require some new ideas and hard work to fix that.

> Yes, I would appreciate for other Z models. How many of them there  
> are?

I've added the current set to the release, so you'll get them next  
time you update.   There are 8 Z values from 1e-6 to 4e-2.

> So, could I change to any initial_Z (making sense of course) value  
> I'd like?
> Could you explain to me what is the difference between mentioned  
> the only Z=0.02 models and different initial_Z values?

If you ask for a Z value for which the system has prebuilt models, it  
will of course use one of those.

If your requested Z is not one of the prebuilt ones, the system will  
load a prebuilt model with the closest available Z, and then modify  
it by adjusting mass fractions.  Hopefully the modified model will  
still be able to converge.  With a large set of pre-builts it seems  
to work.  I've even been able to change Z to 0 for at least some masses.

The main problem comes from models that are of a mass that puts them  
on the boundary between PP versus CNO burning as their main energy  
source.  For them, a change in Z can make a big difference in their  
internal structure.  You may still be able to make the change, but  
you may have to do it in a series of substeps and let things  
reconverge in small steps.

>> You can also make composition changes.  The simplest ways are to  
>> use the change_Y and change_Z controls.  Just set the flag to true  
>> and specify the desired value.
>>       !change_Y = .true.
>>       new_Y = 0.29
>>       !change_Z = .true.
>>       new_Z = 0.018
> It is really great. Are those values applicable to even main and  
> pre-main sequence models?

Yes.

>
>> There are also options for including more details for pre-main- 
>> sequence burning (h2, li7, be7, b8), and alpha chains, etc.  See  
>> mesa/net/public/net_def for more details.
> Is it possible to use that burning to not pre-main sequence starts  
> but to very low mass stars (Msun < 0.08)?

Yes.

> How could I quickly add colors to the output

I've added a routine to star/test/src/run_star.f that creates a log  
of colors info.
Find the following line and change .false. to .true.

          if (.false.) then ! save color magnitude info in log file

Look at the routine write_colors_info to see what's happening.

The latest stuff is revision number 838.  After doing the svn update,  
remove the directory star/zams_models before doing the install.  That  
will cause the install of the star package to create a new  
zams_models directory with all of the Z's.

Let me know how it goes.

Cheers,
Bill