Hot-Star Winds: CIRs, DACs & BRITE Spots

The high luminosities of massive stars drive strong stellar winds, through line scattering of the star's continuum radiation. After summarizing the basic, steady-state CAK theory for wind driving by a power-law ensemble of lines, the discussion here examines the origin of migrating discrete absorption components (DAC's) commonly seen in UV wind lines, with focus on the bright spot model proposed more than 20 years ago by Cranmer & Owocki. Within modern constraints of hot-star photometric variability observed by the BRITE satellites, we present a semi-analytic analysis for the spot size and amplitude needed to produce an overloaded wind that develops a kink transition to a slowly decelerating velocity plateau that form the DAC.