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I have some observational data for a star where I've done aperture photometry to get a partial period. I understand that you need to use other techniques to estimate a period for stars whose period is longer than one night of observing. I know phase folding your data is quite popular. How does one go about phase folding data? Right now, I have multiple days of data plotted that look similar to the picture of the plot I've attached below.

The X-axis is time (Julian date). T1 is the target star, and the c2, c3, and c4 are check stars

Image of my data

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  • $\begingroup$ Do you mean how do you estimate the period, or literally, that you have the period and just want to plot phase-folded data using that period? $\endgroup$
    – ProfRob
    Commented Jun 15, 2022 at 7:31
  • $\begingroup$ @ProfRob I want to estimate the period. I have several observations spread out across multiple days, but because the period is longer than one night of observing I don't have a full period. I would like to use phase-folding (at least I think that's what I want) to estimate a period from all of my independent observations. $\endgroup$
    – Zachary Kennedy
    Commented Jun 15, 2022 at 8:56

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"Phase folding" is just a procedure whereby you replace the time-axis values by t % P, where P is the period and % is the modulo operator that returns the remainder of t/P.

There are are a number of proceduures/algorithms to find the period. The most commonly used in astronomy is probably the Lomb-Scargle periodogram for unevenly spaced data. I highly recommend reading VanderPlas 2018 as a way of understanding the technique. There are commonly used python implementations in scipy and astropy.

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