[Mesa-users] Pre-Correction Frequencies

[Warrick Ball]

> Finally, I noticed that your inlist has
>
>    sigmas_coeff_for_delta_nu_limit = 10
>
> which should terminate the run if ?? increases past the observed value plus 10?.  You might have meant
>
>    sigmas_coeff_for_delta_nu_limit = -10
>
> so that it terminates when ?? *decreases* past the observed value *minus* 10?.

In case this is unclear because the unicode Greek characters appear to have been messed up, "??" is $\Delta\nu$ and "?" is $\sigma$.

W


____________

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,
>
> 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 ?? increases past the observed value plus 
> 10?.  You might have meant
>
>    sigmas_coeff_for_delta_nu_limit = -10
>
> so that it terminates when ?? *decreases* past the observed value *minus* 
> 10?.
>
> 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
>>> 
>>>
>>>   _______________________________________________
>>>   mesa-users at lists.mesastar.org
>>>   https://lists.mesastar.org/mailman/listinfo/mesa-users
>>>   <https://lists.mesastar.org/mailman/listinfo/mesa-users>
>>> 
>>
>>  --
>>  DENNIS STELLO | Associate Professor
>>  School of Physics | Faculty of Science
>>
>>  UNIVERSITY OF NEW SOUTH WALES
>>  Rm136, K15 | University of New South Wales | NSW | 2052
>>  T +61 2 9065 1334  | F +61 2 9385 6060
>>  E d.stello at unsw.edu.au  | W http://www.physics.usyd.edu.au/~stello/
>> 
>> 
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