[Mesa-users] Question about RSP and equilibrium quantities

[Jeremy Sakstein]

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
>>>>>
>>>>>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.mesastar.org/pipermail/mesa-users/attachments/20200121/2c127d0b/attachment-0001.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image.png
Type: image/png
Size: 7667 bytes
Desc: not available
URL: <https://lists.mesastar.org/pipermail/mesa-users/attachments/20200121/2c127d0b/attachment-0004.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image.png
Type: image/png
Size: 19402 bytes
Desc: not available
URL: <https://lists.mesastar.org/pipermail/mesa-users/attachments/20200121/2c127d0b/attachment-0005.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image.png
Type: image/png
Size: 31932 bytes
Desc: not available
URL: <https://lists.mesastar.org/pipermail/mesa-users/attachments/20200121/2c127d0b/attachment-0006.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image.png
Type: image/png
Size: 11526 bytes
Desc: not available
URL: <https://lists.mesastar.org/pipermail/mesa-users/attachments/20200121/2c127d0b/attachment-0007.png>