Context. Mass loss is an important property in evolution models of massive
stars. As up to 90% of the massive stars have a visual or spectroscopic
companion and many of them exhibit mass exchange, mass-loss rates can be
acquired through the period study of massive binaries.
Aims. Using our own photometric observations as well as archival data, we
look for variations in orbital periods of seven massive eclipsing binary
systems in the Cygnus OB2 association and estimate their mass-loss rates and
stellar parameters.
Methods. We use a Bayesian parameter estimation method to simultaneously fit
the period and period change to all available data and a stellar modelling tool
to model the binary parameters from photometric and radial-velocity data.
Results. Four out of the seven selected binaries show non-zero period change
values at two-sigma confidence level. We also report for the first time the
eclipsing nature of a star MT059.Comment: 12 pages, 18 figures, accepted for publication in A&
