A survey for variable young stars with small telescopes: IV -- Rotation Periods of YSOs in IC5070

TL;DR

This study identifies and analyzes rotation periods of young stellar objects in IC5070 using citizen science data, revealing a bi-modal period distribution and linking slow rotation to disk presence, with robust period detection methods.

Contribution

It introduces a multi-algorithm approach for period detection in inhomogeneous data and provides an unbiased sample of YSOs with detailed rotational properties.

Findings

Achieved 85% completeness and 30% contamination with four combined algorithms.

Found a bi-modal period distribution with peaks at three and eight days.

Confirmed the link between disk presence and slower stellar rotation.

Abstract

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.