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Phase Modulation

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Phase Modulation

I’m trying to look at phase modulation using kepler data. I’ve read several papers concerning this and it looks pretty straight foreward. The problem I’m having is that if I restrict the frequency range, I get very different values for the phase. The frequencies and amplitudes change very little.
To make this more clear, the star I’m looking at apparently has both g and p modes. I only want to see the modulation on the p modes (g modes aren’t very good for this type of analysis). There are three dominant p modes ( maybe rotationally split) and two dense sets of smaller frequencies ( g modes(?) and beat frequencies), some of which are comparable to the dominant modes.
For example, using period04 I get phase values for the phase of: 0.989782662, if I use frequency range of 0-nyquist, 0.718183, if I use frequency range 0.02-nyquist, and 0.088020852 if I use frequency range 10-nyquist.
What is wrong? When you add waves together, you add pointwise and it is commutative.
This makes me suspicious of some of my other calculations and of what I’ve read. I often see frequencies restrictions quoted as very low are often instrumental or rotational so are excluded.

Any suggestions will be appreciated.


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