[mesa-users] Kjeldsen correction in astero module

[Dennis Stello]

Hi Santiago,

I think what you are experiencing is the known offset between the 
asymptotic delta_nu and that from the 'average' spacing between overtone 
modes in the observed frequency range.  We start using the asymptotic 
delta_nu as a guide for how close we are to a good solution because it is 
cheap.  When you get close, we start with the radial modes.

As you say, increasing the assumed uncertainty in delta_nu is a way to 
make sure we will find the solution.

However, to make is easier to tune the delta_nu value, the next release of 
MESA will plot the radial modes in the echelle etc as soon as they are 
calculated, giving you a better feel for if you need to decrease or 
increase delta_nu (thanks to Bill).  So after a few test runs, you will 
have a feel for what delta_nu and delta_nu_sigma are most efficient and 
still robust.

Cheers
Dennis/


On Mon, 16 Feb 2015, Santiago Andres Triana wrote:

> Dear Dennis, Kuldeep & MESA users,
>
> Thanks for the hints! I did look into the simplex_results.data and the
> 'a_div_r' column was all zeros. I think the reason is that I was
> providing a 'delta_nu' in the inlist slightly above (about 10%) of the
> observed delta_nu mean (I was thinking that it was better to use a
> value as close as possible to the asymptotic delta_nu there). This
> leads to a correction_b <1 and therefore no correction overall.
>
> Additionally, I had not provided the orders in l0_n_obs(:). It was
> bound to fail indeed.
>
> Now I'm a bit further after providing the radial orders and providing
> the correct delta_nu to match the observed mean (or letting the module
> calculate it by setting delta_nu=-1). The only thing is that there is
> a drop in delta_nu_model as soon as the module starts using the
> l0_freqs (instead of using the Brunt-Vaisala frequency) to calculate
> it (see the figure). In my earlier experiments this drop was
> preventing me from finding good chi2_radial. Now I can tweak
> delta_nu_sigma to make the module calculate delta_nu_model from
> l0_freqs sooner.
>
> Hope this make any sense, please let me know otherwise. Again, many
> thanks for further ideas!
>
> Cheers,
>
> Santiago
>
> On Mon, Feb 16, 2015 at 10:21 PM, Dennis Stello
> <stello at physics.usyd.edu.au> wrote:
>> Hi Santiago,
>>
>> It sounds to me that what you are looking for is in the simplex results
>> file....did you you look there?
>>
>> Cheers
>> Dennis/
>>
>> -------
>> DENNIS STELLO | Senior Lecturer
>> School of Physics A28 | Faculty of Science
>>
>> THE UNIVERSITY OF SYDNEY
>> Rm225, K90 | The University of Sydney | NSW | 2006
>> T +61 2 9036 5108  | F +61 2 9351 7726
>> E stello at physics.usyd.edu.au  | W http://www.physics.usyd.edu.au/~stello/
>>
>>
>>
>> On Sat, 14 Feb 2015, Santiago Andres Triana wrote:
>>
>>> Hi MESA users,
>>>
>>> Playing around with the astero module and simplex, I noticed that the
>>> frequencies, as reported in the sample_#.data files, are not
>>> corrected. They seem to be the raw, uncorrected  frequencies from gyre
>>> although I have specified the 'kjeldsen' method in
>>> inlist_astero_search_controls.
>>>
>>> The inlist is attached. The relevant snippet is this:
>>>
>>>    ! surface corrections
>>>      correction_scheme = 'kjeldsen' ! options are
>>>         ! 'kjeldsen'   Correction of Kjeldsen et al. (2008)
>>>         ! 'cubic'      Cubic correction of Ball & Gizon (2014, eqn 3)
>>>         ! 'combined'   Combined correction of Ball & Gizon (2014, eq 4)
>>>         ! ''           no corrections
>>>      correction_factor = 1
>>>         ! use this fraction of the correction; set to 0 to skip doing
>>> corrections.
>>>      l0_n_obs(:) = -1 ! the observed radial orders (ignored if < 0)
>>>         ! the observed radial orders are used in calculating surface
>>> corrections
>>>         ! if <= 0, use default calculation for radial orders
>>>      correction_b = 4.25d0
>>>
>>>      save_next_best_at_higher_frequency = .true.
>>>      save_next_best_at_lower_frequency = .true.
>>>
>>>
>>> I'm convinced that I'm doing something silly somewhere but cannot
>>> figure out where... any hints or comments are very much appreciated.
>>> Many thanks in advance!
>>>
>>> Cheers,
>>>
>>> Santiago
>>>
>>
>