Overall model fit to Mrk 509 RGS spectrum given in observed frame. RGS 1 and RGS 2 spectra are plotted in orange and cyan dots with arbitrary shift 0.02 counts s⁻¹ Å⁻¹, and errors marked by gray bars. The total model: continuum together with single CTP WA is plotted in red and blue. WA lines are identified with black text, while possible absorption lines on Milky Way - by green text. For instrumental lines, see Appendix A.