The outer wind of γ Velorum




Fine-structure mid-infrared emission lines with critical densities in the regime 104ncrit ≤ 106 cm−3 can be employed to probe the outflow from Wolf–Rayet (WR) stars at radii of ∼1015 cm. Narrow-band mid-infrared imaging and spectroscopy of the nearest WR star to the Sun, γ Velorum is analysed for spatially resolved forbidden line emission in the WR outer wind. The [S iv] 10.52-μm and [Ne ii] 12.81-μm emission regions are found to be spatially extended, compared to unresolved continuum and He and C recombination line emission. The [S iv] and [Ne ii] emission line distributions have a high degree of azimuthal symmetry, indicating a spherically symmetric outflow. A model wind with a modest degree of clumping (clumping factor f ∼ 10) provides a better match to the observations than an unclumped model. The overall line intensity distributions are consistent with a freely expanding, spherically symmetric 1/r2 outflow with constant ionization fraction and modestly clumped density structure.