We investigate the degree to which the nearly symmetric form of X-ray emission lines seen in Chandra spectra of early-type supergiant stars could be explained by a possibly porous nature of their spatially structured stellar winds. Such porosity could effectively reduce the bound-free absorption of X-rays emitted by embedded wind shocks, and thus allow a more similar transmission of redvs. blue-shifted emission from the back vs. front hemispheres. To obtain the localized self-shielding that is… CONTINUE READING
Fig. 3.— X-ray line profiles vs. scaled wavelength x ≡ (λ/λo − 1)c/v∞, overplotted in each panel for optical depth parameters τ∗ = 0.1, 1, 3, 5, and 10 (black, blue, violet, red, green), and normalized to have peaks decrease by 5% for each step in τ∗. The panels compare results for various porosity scale factors h′ = 0, 0.25, 0.5, 1, 2, and 4, ordered from upper left to lower right. The vertical dashed line marks the line center. Note that porosity can make otherwise optically thick cases (i.e. τ∗ = 3, 5, 10) have nearly symmetric profiles, but only with quite large porosity scale factors, h′ > 1, as seen in the lowermost panels.