2009MNRAS.397..849P

A succession of near-infrared (near-IR) spectroscopic observations, taken nightly throughout an entire cycle of SS433's orbit, reveal (i) the persistent signature of SS433's accretion disc, having a rotation speed of ∼500km/s, (ii) the presence of circumbinary disc recently discovered at optical wavelengths by (Blundell, Bowler & Schmidtobreick (2008)) and (iii) a much faster outflow than has previously been measured for the disc wind, with a terminal velocity of ∼1500km/s. The increased wind terminal velocity results in a mass-loss rate of ∼10^–4M_☉/yr. These, together with the newly (upwardly) determined masses for the components of the SS433 system, result in an accurate diagnosis of the extent to which SS433 has super-Eddington flows. Our observations imply that the size of the companion star is comparable with the semiminor axis of the orbit which is given by , where e is the eccentricity. Our relatively spectral resolution at these near-IR wavelengths has enabled us to deconstruct the different components that comprise the Brackett-γ (Brγ) line in this binary system, and their physical origins. With this line being dominated throughout our series of observations by the disc wind, and the accretion disc itself being only a minority (∼15 per cent) contribution, we caution against use of the unresolved Brγ line intensity as an `accretion signature' in X-ray binaries or microquasars in any quantitative way.