Using shell models to investigate clumping in the WN4 star HD 50896

ABSTRACT The spectra of Wolf–Rayet (WR) stars exhibit strong, broad emission lines that originate in the wind. These winds are radiatively driven and susceptible to hydrodynamic instabilities result formation clumps. When modelling WR volume-filling factor (VFF) approach is usually employed treat clumpy winds. However, it based on assumption entire wind mass resides optically thin clumps, which not necessarily justifiable dense To test validity VFF approach, we use a previously described method treating clumping, ‘shell’ study line continuum WN4 star, HD 50896. Our models indicate fully intact spherical shells tension with observed spectra; persistent ‘dip’ occurs at centre. Removing this dip requires our ‘broken’ – highly decoherent laterally. This insinuates 50896, by extension other stars, comprised small laterally confined radially compressed clumps smaller than Sobolev length. We discuss some conditions necessary for be valid.