To be published in:
The Astrophysical Journal
The interacting early-type binary BD+40°4220.
Modelling the colliding winds region+
J.-M. Vreux1 and
1 Institut d'Astrophysique et de Géophysique - Université de Liège, Avenue de Cointe 5, 4000 Liège, Belgium
2 Kitt Peak National Observatory, National Optical Astronomy Observatories++, P.O. Box 26732, Tucson AZ 85726-6732, USA
+ All the observations reported here were obtained at the Observatoire de Haute-Provence and at the Kitt Peak National Observatory.
++ The National Optical Observatories are operated by the Association of Universities for Research in Astronomy, Inc (AURA) under cooperative agreement with the National Science Fondation.
We present the analysis of an extensive set of spectroscopic observations
of the mysterious early-type binary BD+40°4220. A new orbital
solution is derived from the radial velocities of the absorption lines.
We confirm that the secondary star is highly overluminous for its mass.
The absorption lines of both components display phase-locked profile
variations with some of the secondary's lines going into emission between
= 0.20 and
= 0.55. A detailed investigation of the
profile variability of the He II
4686 emission line reveals that
the pattern of variability of this line is very stable. It is shown that
part of the He II
4686 emission is produced in the
wind interaction region between the stars. Most of the emission lines in
the visual spectrum of BD+40°4220 display variations that are
reminiscent of those observed on the He II
4686 line, pointing towards a
We present numerical simulations of emission line profiles in a colliding
winds binary, showing that an important part of the variability observed
in BD+40°4220 can be explained by a colliding winds phenomenon. The
properties of the wind interaction region can be accounted for if we
assume that the secondary star is an evolved object, most probably some
kind of Ofpe/WN9 transition star with a mass loss rate of
~ 5.5 10-6
Myr-1. We finally
discuss the fundamental parameters of the binary, concluding that mass
transfer must have played a crucial role in the evolution of this system.
binaries: eclipsing -- binaries: spectroscopic -- stars: early-type --
stars: individual (BD+40°4220) -- stars: mass loss