The kinematic characteristics of magnetic O-type stars

S. Hubrig$^1$, N.V. Kharchenko$^{1,2}$, M. Sch"oller$^3$

$^1$ Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
$^2$ Main Astronomical Observatory, 27 Academica Zabolotnogo Str., 03680 Kiev, Ukraine
$^3$ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany

Although magnetic fields have been discovered in ten massive O-type stars during the last years,
the origin of their magnetic fields remains unknown.
Among the magnetic O-type stars, two stars, HD,36879 and HD,57682, were identified as candidate runaway stars in the past,
and $theta^1$,Ori,C was reported to move rapidly away from its host cluster.
We search for an explanation for the occurrence of magnetic fields in O-type stars by examining the assumption
of their runaway status.
We use the currently best available astrometric, spectroscopic, and photometric data to calculate
the kinematical status of seven magnetic O-type stars with previously unknown space velocities.
The results of the calculations of space velocities suggest that five out of the seven magnetic O-type stars
can be considered as candidate runaway stars. Only two stars, HD,155806 and
HD,164794, with the lowest space velocities, are likely members of Sco,OB4 and NGC,6530,
respectively. However, the non-thermal radio emitter HD,164794 is a binary system with colliding winds, for which
the detected magnetic field has probably a different origin in comparison to other magnetic O-type stars.

Reference: AN, in print
Status: Manuscript has been accepted