[mesa-users] Some questions on Astero and convection

[João Faria]

Hi

Thank you for the idea Dennis. Doing that has been in my mind for a 
while, although not about the atmosphere issue.
I think it would be important to do the same exercise as for example 
Metcalfe et al.(2009) (2009ApJ...699..373M 
<http://adsabs.harvard.edu/abs/2009ApJ...699..373M>) did with AMP. They 
allowed the algorithm to fit a set of model S computed frequencies 
(without correcting for surface effects). Using the resulting best 
model, they fitted the difference between radial modes of model and 
BiSON data with a power law, arriving at a value of b=4.82 for the 
surface correction which is different from 4.90. I believe CESAM also 
needed to do something similar, but they chose GONG data (not sure about 
this) and got b=4.25 with their treatment of convection.

The reason I haven't done this with MESA yet is in part due to some 
laziness, but also because I'm not sure if this is the best way to do 
it. Probably we should instead calculate frequencies for the MESA 
standard solar model (which is MESA's model S, spectroscopically 
calibrated only) and fit a power law to the (model - BiSON) data to get 
MESA's b value. And I also feel some discomfort in going through so much 
trouble with something as heuristic as the surface corrections...
Anyhow, the study of the atmosphere probably also needs to be done.

Cheers
Jo\E3o


On 01/07/2013 11:21 PM, Dennis Stello wrote:
> Hi Jo�o
>
> For your first question, I would suggest you test it on the Sun using 
> the published BiSON freqs for exmaple (and send the result to this 
> list) ;0)
>
> I will let your other questions open for others to answer.
>
> Cheers
> Dennis/
>
> On Mon, 7 Jan 2013, Jo\E3o 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?
>>
>>    - 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' ?
>>
>>    - 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)?
>>
>>    - 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.
>>
>> 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.
>>
>>
>> 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?
>>
>>
>> Sorry, this turned out a little lengthy.
>> Thank you in advance
>>
>> Jo\E3o Faria
>>
>>
>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.mesastar.org/pipermail/mesa-users/attachments/20130108/5679a7b9/attachment.html>