We seek to establish additional observational signatures of the effects ofclumping in OB star winds. The action of clumping on strategic wind-formedspectral lines is tested to steer the development of models for clumped windsand thus improve the reliability of mass-loss determinations for massivestars.The SiIV 1400 resonance line doublets of B0 to B5 supergiants areanalysed using empirical line-synthesis models. The focus is on decodinginformation on wind clumping from measurements of ratios of the radial opticaldepths (tau_(rad)(w)) of the red and blue components of the SiIV doublet. Weexploit in particular the fact that the two doublet components are decoupledand formed independently for targets with relatively low wind terminalvelocities. Line-synthesis analyses reveal that the mean ratio of tau_(rad)(w)of the blue to red SiIV components are rarely close to the canonical value of ~2 (expected from atomic constants), and spread instead over a range of valuesbetween ~1 and 2. These results are interpreted in terms of a photosphere thatis partially obscured by optically thick structures in the outflowing gas.Thespectroscopic signatures established in this study demonstrate the wide-spreadexistence of wind clumping in B supergiants. The additional information inunsaturated doublet profiles provides a means to quantify the porosity of thewinds.
展开▼
