[mesa-users] Some questions on Astero and convection

[Bill Paxton]

Hi João,

Sorry to be so slow to answer.   This cold doesn't seem to be willing to go away --- over 2 weeks now.  ;-(


On Jan 7, 2013, at 7:22 AM, João Faria wrote:

> Hi all,
> 
> I have been using MESA to do asteroseismology for a while (learned a lot from Instrument Paper 2!) but still have some questions about the astero module. 
> 
> - In the example_astero test, the option of adding an atmosphere to adipls is turned off. I understand that only specific cases would require such an atmosphere going to small optical depths (like WDs probably?) and that including or not the atmosphere will probably only cause a systematic "surface effect". Is it reasonable to do main-sequence and sub-giant fitting without including the atmosphere
beyond me.   

> - in a related question, the add_atmosphere = .true. option adds a 'Paczynski_grey' atmosphere to the model. Can we use it with either which_atm_option = 'photosphere_tables' or which_atm_option ='Krishna_Swamy' ? 
> 
in addition to Paczynski, you can use any of the T(tau) integration scheme (such as Krishna_Swamy).
but you can't use tables since we are just using them for specific optical depths, not as a way to construct an atmosphere.

> - yet another related question: is it ok to create a pre-ms model with 
> which_atm_option ='Krishna_Swamy' if we have it relaxed for 200 steps (pre_ms_relax_num_steps = 200)?
> 
that should work.   if you get convergence problems, try waiting until you get near zams before switching atm options.

> - MESA gives the possibility of calculating delta_nu from a linear fit to the radial modes. This will also calculate delta_nu_sigma as the error in the fit, but this error will usually be one or two orders of magnitude smaller than the "real" error in delta_nu. Is it possible to add an option to use delta_nu_sigma from the inlist even if doing the fit? Something like setting delta_nu = -1 but still using, for example, delta_nu_sigma = 5.0 if set in the inlist.
that sounds okay to me --- please get Dennis' opinion.  He's my "boss" for questions like this.  ;-)

> Still on the astero module, I found a very tiny bug in the echelle plot routine. In line 258 of the file pgstar_echelle_plot.f it should say
>     if (have_nonradial) call show_model(l3_freq_corr(i))
> instead of
>     if (have_nonradial) call show_model(l2_freq_corr(i))
> otherwise the l=3 modes appear "connected" to the l=2 ones.

Thanks -- I've now made the fix,


> 
> 
> About the convection I just have a question/wish. Will MESA in the near future be able to calculate convection according to the treatment of Canuto & Mazzitelli? Can we expect much difficulty in implementing something like what CESAM does in other_mlt?

I don't have any plans to add the Canuto & Mazzitelli scheme.  But it should be possible to do using other_mlt if you'd like to try.

Cheers,
Bill



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