[Mesa-users] Setting the value of omega/omega_critical

AVG avargar2 at hotmail.com
Fri Mar 25 16:22:05 UTC 2022

Hi Simon,

Thanks for your time. What I want to do is obtaining the pulsation 
frequencies of some stars at some given values of their omega (in 
different moments of each star), so I think I will have to save and 
restart as you say to be able to perform the work.

Thank you again for all!

Antonio Varo

On 25/3/22 2:27, Simon Murphy wrote:
> Hi Antonio,
> omega will always change as a function of time because angular 
> momentum is conserved and the stellar structure is not constant. The 
> star becomes more centrally condensed and the radius increases.
> So while your initialisation of rotation will achieve a certain value 
> of omega/omega_c /at some point/, it will not stay that way for long. 
> Moreover, the star will not remain a uniform rotator, either. If 
> you're able to plot the internal rotation rate as a function of (r/R) 
> at a few ages, this will become apparent, especially while the star is 
> still contracting.
> The meaningful question then becomes 'what do you hope to achieve'? 
> That is, given the options, do you want to initialise uniform rotation 
> at some age and let it evolve as perhaps a star would? Or do you want 
> to force uniform rotation throughout the evolution, which might be 
> achieved with a further save&restart with a renewed fixed 
> omega/omega_c some time around your model 600 (and perhaps 700 too)? 
> Or something else entirely?
> - Simon
> ------------------------------------------------------------------------
> *From:* AVG <avargar2 at hotmail.com>
> *Sent:* 25 March 2022 01:10
> *To:* Simon Murphy <simon.murphy at sydney.edu.au>; 
> mesa-users at lists.mesastar.org <mesa-users at lists.mesastar.org>
> *Subject:* Re: [Mesa-users] Setting the value of omega/omega_critical
> Hello Simon!
> Firstly, thank you very much for your time.
> I attach the plots (Figure_5*) of the stellar radius, the nuclear 
> burning and the original plot (just to make it easier to compare).
> I don't know how to take these plots. I see that the radius decreases 
> (and so the omega increases). However, this situation doesn't change 
> when I run the simulation for 2500 Myears (for example), and I always 
> get a changing value of the omega. I also attach the plots of the 
> simulation that ends at 2500 Myears (Figure_1*).
> Best regards,
> Antonio Varo
> On 23/3/22 22:33, Simon Murphy wrote:
>> Hi Antonio,
>> you're setting rotation using the near_zams parameters. I think it's 
>> important to note that this is not the same as 'after the ZAMS'. I 
>> suspect the star is still contracting a little, which is why the 
>> rotation is still increasing after it is initially set.
>> To confirm (and for the benefit of future readers), please could you 
>> plot what's happening with (a) the stellar radius, and (b) the 
>> nuclear burning, alongside your rotation plot?
>> cheers,
>> - Simon
>> ------------------------------------------------------------------------
>> *From:* Mesa-users <mesa-users-bounces at lists.mesastar.org> 
>> <mailto:mesa-users-bounces at lists.mesastar.org> on behalf of AVG via 
>> Mesa-users <mesa-users at lists.mesastar.org> 
>> <mailto:mesa-users at lists.mesastar.org>
>> *Sent:* 24 March 2022 04:34
>> *To:* mesa-users at lists.mesastar.org 
>> <mailto:mesa-users at lists.mesastar.org> 
>> <mesa-users at lists.mesastar.org> <mailto:mesa-users at lists.mesastar.org>
>> *Subject:* [Mesa-users] Setting the value of omega/omega_critical
>> Dear all,
>> I am trying to simulate a rotating star with a given value of its
>> omega/omega_critical, but I find that this parameter varies strongly in
>> the first 20 Myears of the simulation since the ZAMS starts (I am
>> specially interesed on what happens in those first 20 Myears after the
>> ZAMS, as the work I am doing is focused on some previous results
>> obtained until that time).
>> In my simulations I turn on the rotation at the begining of ZAMS, and
>> shortly after it starts the value of its omega changes quickly, as we
>> can see in the image I attach. I want to set the value of the omega
>> along the simulation, as I need to analyse results obtained with GYRE
>> for some specific omegas (so the increasing behaviour of the omega makes
>> it really difficult for me).
>> I also attach the inlist I have used.
>> Could someone give me some tips on this?  Any help will be appreciated.
>> Best regards,
>> Antonio Varo
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