[Mesa-users] Regarding some clarifications

[Thomas Steindl]

Hi Nathalie, 

just wanted to chime in to this topic as well. I have done extensive work looking into how to use (different versions of) chi-square in order to arrive at best fitting models and expectation values. I have learned that it is beneficial to test the methodology for its performance. I used perturbed model data to test how reliable the methodology produces expectation values that agree with the model’s values. For the specific case of young pulsating delta scuti stars (mode id + spectroscopic parameters) it matters how you „pick“ the models you use for the extraction of expectation values. I was very surprised when I first saw this! 

If you compare different model setups, I would advise the use of information criteria like the Akaike information criterion (AIC) or the Bayesian information criterion (BIC). Such criteria can give you information about the quality of your modelling approach.  

You can find some of that here: https://ui.adsabs.harvard.edu/abs/2022A%26A...664A..32S/abstract

Good luck with your project,
Thomas Steindl
__________________________________________________________________

Thomas Steindl, PhD
University of Innsbruck | Institute for Astro- and Particle Physics
Tel: +43 512507 52031
Mail: thomas.steindl at uibk.ac.at
Homepage: www.thomassteindl.com

> 
> On Fri, May 5, 2023 at 11:46 AM Nathali Perera via Mesa-users <mesa-users at lists.mesastar.org <mailto:mesa-users at lists.mesastar.org>> wrote:
>> Hello everyone,
>> I'm a beginner to MESA and I'm working with this software for my final year research project. I'm currently modeling detached binary star systems which have almost similar masses like 1.875 and 1.856 solar mass. Since the binary star system is detached and not assumed to be mass transferring, these two stars were modeled as single evolutionary stars. Then I tried to change their mass (starting from 1.75 to 1.9 with a step size of 0.05), chemical composition (changes 0.01, 0.014, 0.018), mixing length (change as 1.8 and 0.2), and overshooting (0.005, 0.01,0.015)to see the effect for their evolutionary tracks. My question is, if there is more than one evolutionary track that intersects the star's error box, how do we know the best suitable track for that star? 
>> 
>> Secondly, I would like to clarify some other questions regarding the code which I used. How can we select when to use 'kap_file_prefix' or 'use_type2_opaities'? Should we use 'kap_file_prefix' for stars that are rich in hydrogen and 'use_type2_opacities' for stars that have heavy metals? If I use both of these two conditions at the same time will MESA select one condition among them?
>> 
>> And if anyone sees any mistake in my code, please let me know. I would like to learn and correct my mistakes. 
>> 
>> And I'm using mesa release r22.11.1.I have attached a figure that I obtained from my work and in that figure, I have marked the binary star system with error bars and several evolutionary tracks.
>> 
>> Thank You
>> Nathali Perera
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> 
> 
> -- 
> 
> Dr Meridith Joyce 
> Marie Sklodowska-Curie Actions Widening Fellow
> CSFK Konkoly Observatory, Budapest, Hungary 1121
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