Broad emission lines of helium and either carbon or nitrogen characterize these stars, which evolve from luminous blue variables.
Atmospheric models of these stars have two key parameters: a "transformed radius" that is proportional to the radius at which Rosseland optical depth equals twenty, and an e fective temperature that is computed iteratively while accounting for line blanketing. Local thermodynamic equilibrium and plane-parallel geometry are not valid assumptions for these stars' atmospheres. The centers of about ten percent of planetary nebulae contain one of these stars. So-called "slash" stars are spectroscopically intermediate between these stars and O-type stars. At low metallicity and high rotation rate, the inner core of one of these stars becomes a hypernova in the "collapsar" model of long-duration gamma-ray bursts. Broad emission lines of helium and either carbon or nitrogen characterize these stars, which evolve from luminous blue variables. For 10 points, identify these doubly-eponymous stars that have extremely high rates of mass loss.
Atmospheric models of these stars have two key parameters: a "transformed radius" that is proportional to the radius at which Rosseland optical depth equals twenty, and an e fective temperature that is computed iteratively while accounting for line blanketing.
Wolf-Rayet ("wolf"-ray-et or "wolf-rye"-ay) stars [or Class WR stars; or Class WN stars; or Class WC stars]