Average spectrum of SS 433 (top) after removal of the Hα jet components and division of the interstellar spectrum (third from top; offset in intensity by −0.5 for clarity). Also shown are the absorption spectrum from Earth’s atmosphere (bottom; reduced by a factor of 2 in intensity and offset by −1.0) and the spectrum of 9 Cep (B2 Ib; second from top; offset in intensity by −0.2).