Direct Spectroscopic Observations of Clumping in O-Star Winds

We report the detection and monitoring of transient substructures in the radiation-driven winds of five massive, hot stars in different evolutionary stages. Clumping in the winds of these stars shows up as variable, narrow subpeaks superposed on their wide, wind-broadened (optical) emission lines. Similar patterns of emission-line profile variations are detected in the Of stars ζ Puppis and HD 93129A, in the more evolved hydrogen-rich, luminous, Of-like Wolf-Rayet nitrogen stars HD 93131 and HD 93162, and in the more mass-depleted Wolf-Rayet carbon star in γ 2 Velorum. These observations strongly suggest that stochastic wind clumping is a universal phenomenon in the radiation-driven, hot winds from all massive stars, with similar clumping factors in all stages of mass depletion.