A survey for variable young stars with small telescopes – IV. Rotation periods of YSOs in IC 5070

Abstract

Studying rotational variability of young stars is enabling us to investigate a multitude of properties of young star-disc systems. We utilize high cadence, multiwavelength optical time series data from the Hunting Outbursting Young Stars citizen science project to identify periodic variables in the Pelican Nebula (IC 5070). 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 per cent and a contamination of 30 per cent in identifying periods in inhomogeneous data sets. The best performing methods are periodograms that rely on fitting a sine curve. Utilizing Gaia EDR3 data, we have identified an unbiased sample of 40 periodic young stellar objects (YSOs), without using any colour or magnitude selections. With a 98.9 per cent probability, we can exclude a homogeneous YSO period distribution. Instead, we find a bi-modal distribution with peaks at 3 and 8 d. The sample has a disc fraction of 50 per cent, and its statistical properties are in agreement with other similarly aged YSOs populations. In particular, we confirm that the presence of the disc is linked to predominantly slow rotation and find a probability of 4.8 × 10−3 that the observed relation between period and presence of a disc 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 IC 5070.

A Zwicky Transient Facility Look at Optical Variability of Young Stellar Objects in the North America and Pelican Nebulae Complex

“…In order to test the quality of our derived periods, we compared them to the periods published in Bhardwaj et al (2019) and Froebrich et al (2021). Both papers considered objects in the Pelican Nebula region (see Figure 1).…”

“…Of the 40 periodic variables identified in Froebrich et al (2021), 32 are within 2″ of a source in our sample, of which 20 we classify as periodic in Q − M space. All 20 have periods within 5% of our derived periods.…”

“…The results of long-term photometric monitoring observations of the region have been reported by Poljančić et al (2014), Ibryamov et al (2015), and Ibryamov et al (2018), providing detailed analyses of small samples of stars based on decades of multicolor data from numerous observatories. Bhardwaj et al (2019) found 56 periodic variables in the Pelican Nebula region, visually classifying an additional 11 variables as nonperiodic while Froebrich et al (2021) identified 59 periodic variables, many of which overlap with the Bhardwaj et al (2019) sample.…”

A survey for variable young stars with small telescopes: VI – Analysis of the outbursting Be stars NSW 284, gaia 19eyy, and VES 263

“…The project Hunting Outbursting Young Stars (HOYS) is one of the endeavours designed to overcome this deficit, by collecting observations from a multitude of small telescopes from professional and amateur observatories, all using a pre-defined observing strategy and a specific set of target regions (see overview paper by Froebrich et al 2018). In the first HOYS papers we have, for example, presented a study of rotation in one star forming region (Froebrich et al 2021), a follow-up study of spot properties in the same region (Herbert et al 2023), and an analysis of the variability in a specific source that is caused by eclipses from structures in a protoplanetary disk (Evitts et al 2020), among other findings. In this paper we take a more holistic view -we aim to select prospective young stars in all 25 HOYS target regions, using data from Gaia, collate information about these samples, and study general variability properties among those samples.…”

A ZTF Look at Optical Variability of Young Stellar Objects in the North America and Pelican Nebulae Complex

“…The results of long-term photometric monitoring observations of the region have been reported by Poljančić et al (2014), Ibryamov et al (2015), and Ibryamov et al (2018), providing detailed analyses of small samples of stars based on decades of multi-color data from numerous observatories. Bhardwaj et al (2019) found 56 periodic variables in the Pelican Nebula region, visually classifying an additional 11 variables as non-periodic while Froebrich et al (2021) identified 59 periodic variables, many of which overlap the Bhardwaj et al (2019) sample.…”