A survey for variable young stars with small telescopes: IV -- Rotation
  Periods of YSOs in IC5070
  Studying rotational variability of young stars is enabling us to investigate
a multitude of properties of young star-disk systems. We utilise high cadence,
multi-wavelength optical time series data from the Hunting Outbursting Young
Stars citizen science project to identify periodic variables in the Pelican
Nebula (IC5070). A double blind study using nine different period-finding
algorithms was conducted and a sample of 59 periodic variables was identified.
We find that a combination of four period finding algorithms can achieve a
completeness of 85% and a contamination of 30% in identifying periods in
inhomogeneous data sets. The best performing methods are periodograms that rely
on fitting a sine curve. Utilising GaiaEDR3 data, we have identified an
unbiased sample of 40 periodic YSOs, without using any colour or magnitude
selections. With a 98.9% probability we can exclude a homogeneous YSO period
distribution. Instead we find a bi-modal distribution with peaks at three and
eight days. The sample has a disk fraction of 50%, and its statistical
properties are in agreement with other similarly aged YSOs populations. In
particular, we confirm that the presence of the disk is linked to predominantly
slow rotation and find a probability of 4.8$\times$10$^{-3}$ that the observed
relation between period and presence of a disk has occurred by chance. In our
sample of periodic variables, we also find pulsating giants, an eclipsing
binary, and potential YSOs in the foreground of IC5070.
