Abstract
On five Fabry-Perot interferograms radial velocities from the Hα line at 338 points on and around the "ring" nebula NGC 2359 have yielded +71.0 ± 7.5 km s-1 for the moan overall velocity of the H II region. This value is taken to represent the radial velocity of the WN5 star HD 56925, the source of the excitation of the H II region. Using the Schmidt model the kinematic distance of the object is 4.0 kpc. The velocity field has structure clearly related to the morphology of the region. Attention is concentrated on two well defined elliptical filaments around the exciting star. The mean velocities of outer and inner filaments are 84 ± 5 and 56 ± 7 km s-1 respectively showing clearly that with respect to the star the outer ring is receding while the inner one approaching the observer. This peculiarity is strong support to the model we suggest that the ejection is essentially non-isotropic, and it has occurred in localized regions on the opposite hemispheres of the rotating `WN5 star with axis of rotation close to the line of sight. It is suggested that the central WR may also follow at present a similar pattern of mass loss from nearly diametrically opposite spots on the star.
