[Mesa-users] Question about RSP and equilibrium quantities

[Radek Smolec]

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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