is computed with $v_{\rm therm}=\sqrt{\frac{2k_{\rm B}T}{\mu m_H}}$, where $k_{\rm B}$ is the Bolztmann constant, $\mu m_H$ is the average mass per particle; $\mu\simeq 0.6$ for fully ionized solar-metallicity gas. The temperature $T$ is taken from our calculations. The microturbulent velocity $v_{\rm turb}$ is set to 200 . Then, we build absorption spectrum for each line ($F_{\lambda}$ around each feature) and compute EWs: $$EW=\int{1-\exp{(-\tau_{\lambda})}}d\lambda.$$

One important problem we are able to address here, is the difference of measuring absorption line EWs taking into account all the relevant atomic physics, i.e., bound-bound and bound-free transitions, which extend from the SED, in contrast with measurements of EWs made using as the continuum the absorbed SED. We call the first type unabsorbed EWs and the second one absorbed EWs. Figure \[isolated\_L2\_tbabs\], depicts this problem in a visual manner.

For instance in a model where a single absorber is present (wabs1), we find difference between the level of SED (red dashed line in Figures), and the level of the absorbed SED (gray dashed line), which is the result of the SED’s radiation passing through wabs1. It is clear that measuring EWs using these two different continuum levels will give different results.

Likewise applied to a 