We present mid-infrared spectra of the microquasar SS 433 obtained with the Infrared Space Observatory ( spectroscopic mode of ISOPHOT ) and compare them to the spectra of four Wolf-Rayet stars .
The mid-infrared spectrum of SS 433 shows mainly H i and He i emission lines and is very similar to the spectrum of WR 147 , a WN8 ( h ) +B0.5V binary with a colliding wind .
The 2–12 \mu m continuum emission corresponds to optically thin and partially optically thick free-free emission from which we calculate a mass loss rate of 1.4 - 2.2 \times 10 ^ { -4 } M _ { \odot } \mathrm { yr } ^ { -1 } if the wind is homogeneous and a third of these values if it is clumped , which is consistent with a strong WN stellar wind .
We propose that this strong wind outflows from a geometrically thick envelope of material surrounding the compact object like a stellar atmosphere , imitating the Wolf-Rayet phenomenon .