Terminal speeds and ion fractions from [Ca IV] 3.207 mu m in three single WN stars

We report on the forbidden emission lines of [Ca IV] at 3.207 mum and [Ne I II] at 15.56 mum based on Infrared Space Observatory observations. The data set consists of three single Wolf-Rayet stars (WR 1, WR 134, and WR 136) a nd three binary systems (WR 11, WR 146, and WR 147). For the single stars, only the [Ca IV] line was observed. Our primary objectives are to determine the wind terminal speed from the emission-line widths, derive ion number f ractions, and discuss the relation between emission profile shapes and wind flow geometry. Compared to previous determinations of the terminal speed, we find values that are similar or somewhat smaller. Interestingly, the lin e width at the continuum level is typically 10%-30% broader than at the hal f-maximum level. The extra broadness suggests the effect of turbulence in t he wind. For the ion fraction, we assume that calcium is not enriched in an y of the W-R winds. Ion fractions of Ca+3 and Ne+2 are derived for the bina ry systems and found to be consistent with previously published values. For the new observations of the single WN stars, all of the ion fractions for Ca+3 have similar values, which are close to the maximum expected value, th us suggesting that Ca+3 is the dominant ion at large radii in the wind. Fin ally, the line profile shapes in the binaries WR 11, WR 146, and WR 147 app ear asymmetric, as might be expected from such systems. For WR 136, the [Ca IV] profile is flat-topped, consistent with a spherical flow. For WR 1 and WR 134, the [Ca IV] profiles are too weak to draw conclusions about the wi nd flow geometry.