2007MNRAS.380..263C

We present new 8200-8900 Å high-resolution spectroscopic observations of the unusual accreting source SS433. The spectra are highly variable on a night-to-night basis, and are dominated by emission from the Paschen series and Oi emission. Differences in line profiles between the two species suggest that they arise in kinematically distinct and highly variable circumstellar regions. Moreover, the strength of Oi emission argues against identifying the mass donor as a Wolf-Rayet star since we might expect oxygen to be depleted by the CNO cycle in such a star. Weak Ni absorption lines are present, which, if arising in the photosphere of the mass donor would imply a spectral type of B5 or later. However, no evidence was found for orbital modulation in their radial velocity curves suggesting that they too arise in the accretion-driven outflow. Finally, by analogy to the massive close binary RY Scuti, we suggest that the recent detection of a mid-infrared excess attributed to warm dust may arise in a circumbinary disc, implying that SS433 hosts a rich, highly structured circumstellar environment driven by the high mass-transfer rate from the mass donor.