[Mesa-users] Pre-Correction Frequencies

[Warrick Ball]

Hi Erica,

Dennis is right: the coefficients of the cubic correction aren't constrained to have the same sign as the surface correction we'd need for the Sun, nor to be especially small or anything, so nothing prevents this from happening.

>From your output, it looks like you're using r12778 or earlier.  If you'd like to constrain the coefficient, you can edit the subroutines `get_cubic_...` in `star/astero/src/astero_support.f`. e.g. replace

     a3 = Xty/XtX

with something like

     a3 = Xty/XtX
     if (a3 > 0) a3 = 0

Coincidentally I've just run into the same issue so will be looking more closely at why this happens, when I previously haven't found it to be an issue.

Finally, I noticed that your inlist has

     sigmas_coeff_for_delta_nu_limit = 10

which should terminate the run if Δν increases past the observed value plus 10σ.  You might have meant

     sigmas_coeff_for_delta_nu_limit = -10

so that it terminates when Δν *decreases* past the observed value *minus* 10σ.

Cheers,
Warrick

____________

Warrick Ball
Postdoc, School of Physics and Astronomy
University of Birmingham, Edgbaston, Birmingham B15 2TT
W.H.Ball at bham.ac.uk
+44 (0)121 414 4552


On Wed, 23 Dec 2020, mesa-users at lists.mesastar.org wrote:

> Hi Erica,
>
> w/o having looked at your attachments (except the plots) my guess is that you 
> found too different models in the two cases (Kjeldsen vs Ball).  The 
> (pre-corrected) model found using Ball is clearly further from the 'best' 
> model (its density is further from the observed) but the correction takes 
> care of that.
>
> However, if by 'look a little strange' you mean that the correction goes in 
> the 'wrong direction', then it might be because you are not limiting the 
> fitting coefficients.
> I recall seeing similar issues when using the Kjeldsen correction (in a MESA 
> simplex fit) for some stars.
>
> But perhaps Warrick can chip in as well.
>
> Best
> Dennis/
>
> On 23/12/2020 15:08, Erica Sawczynec wrote:
>>  Hi all!
>>          I have a few questions about the frequency output in the
>>  simplex_results.data file. I am trying to make an echelle diagram that
>>  shows the frequencies before and after correction from the best fit MESA
>>  model. When I use the Kjeldsen correction I am able to plot l0_freq_# and
>>  get the results I expect, frequencies that lean slightly to the right of
>>  the input frequencies, but when I use the Ball & Gizon correction the
>>  uncorrected frequencies look a little strange. I’ve attached an image
>>  below that demonstrates what I mean.
>>
>>  So I just wanted to be sure anything labeled l(0,1,2)_freq_# is mean to be
>>  the original output model frequency before correction and
>>  l(0,1,2)_freq_corr_# is meant to be the frequency after using either the
>>  Kjeldsen or Ball & Gizon correction. If that is true, I was wondering why
>>  the Ball & Gizon pre-corrected frequencies look like that? If not, what is
>>  the proper column I should be using to plot the uncorrected model
>>  frequencies?
>>
>>  I’ve also attached my inlist and simplex_results.data file below, let me
>>  know if there is anything else I can provide that would be useful!
>>  Thanks,
>>  Erica
>> 
>>
>>  _______________________________________________
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>> 
>
> -- 
> DENNIS STELLO | Associate Professor
> School of Physics | Faculty of Science
>
> UNIVERSITY OF NEW SOUTH WALES
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