[Mesa-users] Question about RSP and equilibrium quantities

[Jeremy Sakstein]

I just tried several different averaging procedures and it seems that the
two lines are still there. Maybe there really is a very low-period doubling
phenomenon going on. I see this in other variables such as luminosity too.

One or two procedures did give me a single line but they are way off from
what the average is by eye.

On Tue, Jan 21, 2020 at 10:10 AM Jeremy Sakstein <sakstein at hawaii.edu>
wrote:

> To average I just pick a pulsation cycle, add up the radius over that
> cycle and divide by the number of data points.
>
> On Tue, Jan 21, 2020 at 10:09 AM Radek Smolec <smolec at camk.edu.pl> wrote:
>
>> So I'm confused; you wrote:
>>
>>> I am taking a single pulsation cycle and averaging over the radius
>>> throughout the cycle
>>>
>> how do you average? It seems the pulsations nicely  repeat and problem is
>> in the averaging procedure.
>> If you are not averaging, but want to look at radius at some specific
>> pulsation phase, then you need to interpolate, as RSP time steps are not
>> synchronised with pulsation phase.
>> Radek
>>
>>
>> wt., 21 sty 2020 o 21:01 Jeremy Sakstein <sakstein at hawaii.edu>
>> napisał(a):
>>
>>> I think it does alternate. Here is a zoom in over 20 cycles:
>>>
>>> [image: image.png]
>>>
>>> Here is a plot with 3 alternating cycles:
>>>
>>> [image: image.png]
>>>
>>> The three colours correspond to the different cycles so with the
>>> exception of the number/position of data points it appears the plots are
>>> identical. Here's the radius, which also looks identical:
>>>
>>> [image: image.png]
>>>
>>> I'm not using the time-steps at all. I made these points by picking out
>>> the data points where the pulsation cycle (rsp_num_periods) is fixed to
>>> some value.
>>>
>>>
>>> On Tue, Jan 21, 2020 at 9:47 AM Radek Smolec <smolec at camk.edu.pl> wrote:
>>>
>>>> So does it alterante between two values?
>>>> Can you attach a plot of a few consecutive pulsation cycles, maybe with
>>>> zoom at radii maxima or minima?
>>>> If you get alteranating values of average radius the consecutive
>>>> pulsation cycles must differ.
>>>>
>>>> One other idea, do you interpolate for start of the pulsation cycle? If
>>>> you use the time steps as used by rsp, without interpolation, then some
>>>> scatter in the averaged radius is possible (but likely not alternations).
>>>> Radek
>>>>
>>>>
>>>> wt., 21 sty 2020 o 20:39 Jeremy Sakstein <sakstein at hawaii.edu>
>>>> napisał(a):
>>>>
>>>>> Hi Both,
>>>>>
>>>>> I don't think it's periodu doubling because I just see a single
>>>>> harmonic when I plot the light curves.
>>>>>
>>>>> Sorry to be unclear. I am plotting the average stellar (surface)
>>>>> radius for each pulsation cycle.
>>>>>
>>>>> On Tue, Jan 21, 2020 at 9:37 AM Radek Smolec via Mesa-users <
>>>>> mesa-users at lists.mesastar.org> wrote:
>>>>>
>>>>>> Hi Jeremy,
>>>>>>
>>>>>> It is difficult to guess what is happening without more detailed
>>>>>> information. The effect you describe may be physical: for example
>>>>>> low-amplitude period doubling phenomenon may be present in your model and
>>>>>> then averages for even and odd pulsation cycles will differ.
>>>>>> With such large difference you should be able to figure it out simply
>>>>>> looking at the light or radius variation curve.
>>>>>>
>>>>>> For the general point; what you consider as "true equilibriu model"?
>>>>>> RSP starts from equilibrium model, but it doesn't mean that the linear
>>>>>> properties of the model, such as pulsation period, will not change when
>>>>>> model pulsates at full amplitude.
>>>>>> It is best to develop own procedures for computing such quantities as
>>>>>> mean magnitude, radius, etc.
>>>>>> Cheers,
>>>>>> Radek
>>>>>>
>>>>>>
>>>>>> wt., 21 sty 2020 o 20:20 Jeremy Sakstein <sakstein at sas.upenn.edu>
>>>>>> napisał(a):
>>>>>>
>>>>>>> Hi Everyone,
>>>>>>>
>>>>>>> I have a quick question about finding the equilibrium values of the
>>>>>>> stellar parameters when using RSP Cepheid.
>>>>>>>
>>>>>>> At the moment, I am taking a single pulsation cycle and averaging
>>>>>>> over the radius throughout the cycle but this seems to give me two (very
>>>>>>> closely separated values).
>>>>>>>
>>>>>>> Below I am plotting radius vs pulsation number. As you can see, I
>>>>>>> end up with two very closely separated values for the average. Is this
>>>>>>> because the model is changing ever so slightly between pulsations? If so,
>>>>>>> why does it converge to two values and not a small scatter about the mean?
>>>>>>>
>>>>>>> [image: image.png]
>>>>>>>
>>>>>>> On a more general point, is it possible to extract the true
>>>>>>> equilibrium model from the output rather than taking an average?
>>>>>>>
>>>>>>> Cheers,
>>>>>>>
>>>>>>> Jeremy
>>>>>>> _______________________________________________
>>>>>>> mesa-users at lists.mesastar.org
>>>>>>> https://lists.mesastar.org/mailman/listinfo/mesa-users
>>>>>>>
>>>>>>> _______________________________________________
>>>>>> mesa-users at lists.mesastar.org
>>>>>> https://lists.mesastar.org/mailman/listinfo/mesa-users
>>>>>>
>>>>>>
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