Lennon, D. J.; Drew, J. E.; Wright, N. J.; Herrero, A.; Berlanas, S. R.
Bibliographical reference
Monthly Notices of the Royal Astronomical Society, Volume 484, Issue 2, p.1838-1842
Description
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.
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