Disentangling the spatial substructure of Cygnus OB2 from Gaia DR2

S. R. Berlanas, N. Wright, A. Herrero, J. E. Drew, D. J. Lennon

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23 Citations (Scopus)
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For the first time, we have explored the spatial substructure of the Cygnus OB2 association using parallaxes from the recent second Gaia data release. We find significant line-of-sight substructure within the association, which we quantify using a parametrized model that reproduces the observed parallax distribution. This inference approach is necessary due to the non-linearity of the parallax distance transformation and the asymmetry of the resulting probability distribution. Using a Markov Chain Monte Carlo ensemble sampler and an unbinned maximum likelihood test, we identify two different stellar groups superposed on the association. We find the main Cygnus OB2 group at ∼1760 pc, further away than recent estimates have envisaged, and a foreground group at ∼1350 pc. We also calculate individual membership probabilities and identify outliers as possible non-members of the association.

Original languageEnglish
Pages (from-to)1838–1842
Number of pages5
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Early online date16 Jan 2019
Publication statusPublished - 1 Apr 2019


  • astro-ph.SR
  • astro-ph.GA
  • Stars: distances
  • Associations: individual: Cygnus OB2
  • Stars: early-type
  • Stars: massive
  • Open clusters
  • Parallaxes
  • Astrometry


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