A survey for variable young stars with small telescopes: IV - Rotation Periods of YSOs in IC 5070

Dirk Froebrich, Efthymia Derezea, Aleks Scholz, Jochen Eislöffel, Siegfried Vanaverbeke, Alfred Kume, Carys Herbert, Justyn Campbell-White, Niall Miller, Bringfried Stecklum, Sally V Makin, Thomas Urtly, Francisco C Soldán Alfaro, Erik Schwendeman, Geoffrey Stone, George Fleming, Rafael Gonzalez Farfán, Tonny Vanmunster, Michael A Heald, Esteban Fernández MañanesTim Nelson, Heinz-Bernd Eggenstein, Franky Dubois, Ludwig Logie, Steve Rau, Klaas Wiersema, Nick Quinn, Diego Rodriguez, Rafael Castillo García, Thomas Killestein, Tony Vale, Domenico Licchelli, Marc Deldem, Georg Piehler, Dawid Moździerski, Krzysztof Kotysz, Katarzyna Kowalska, Przemysław Mikołajczyk, Stephen R L Futcher, Timothy P Long, Mario Morales Aimar, Barry Merrikin, Stephen Johnstone, Pavol A Dubovský, Igor Kudzej, Roger Pickard, Samuel J Billington, Lord Dover, Tarik Zegmott, Jack J Evitts, Alejandra Traspas Munia, Mark C Price

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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 (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 % 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 Gaia EDR3 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 × 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 IC 5070.

Original languageEnglish
Article numberstab2082
JournalMonthly Notices of the Royal Astronomical Society
Publication statusE-pub ahead of print - 21 Jul 2021


  • stars: formation
  • pre-main sequence
  • stars: variables
  • T Tauri
  • Herbig
  • Ae/Be
  • stars: rotation


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