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Keywords:

  • accretion, accretion discs;
  • stars: individual: SS433;
  • stars: mass-loss;
  • stars: winds, outflows;
  • ISM: jets and outflows

ABSTRACT

The Galactic microquasar SS433 launches oppositely directed plasma jets at speeds approximately a quarter of the speed of light along an axis which precesses, tracing out a cone of polar angle ∼20°. Occasionally the system exhibits a major flare when the intensity of its emission, especially at radio wavelengths, increases significantly and rapidly. We present an analysis of high-resolution, almost-nightly optical spectra obtained before, during and after a major flare, whose complex emission lines are deconstructed into single Gaussians and we demonstrate the different modes of mass loss in the SS433 system. During our monitoring, an initial period of quiescence was followed by increased activity which culminated in a radio flare. In the transition period, the accretion disc of SS433 became visible in Hα and He i emission lines and remained so until the observations were terminated; the line-of-sight velocity of the centre of the disc lines during this time behaved as though the binary orbit has significant eccentricity rather than being circular, consistent with three recent lines of evidence. After the accretion disc appeared, its rotation speed (as measured by the separation of the Hα disc emission lines) increased steadily from 500 to 700 km s−1. The launch speed of the jets first decreased then suddenly increased. At the same time, as the jet launch speed increased, the wind from the accretion disc doubled in speed. Two days afterwards, the radio flux exhibited a flare. These data suggest that a massive ejection of material from the companion star loaded the accretion disc and the system responded with mass loss via different modes that together comprise the flare phenomena. We find that archival data reveal similar behaviour, in that when the measured jet launch speed exceeds 0.29c, this is invariably simultaneous with, or a few days before, a radio flare. Thus the manifestation of a major flare is surmised to comprise the overloading of the accretion disc manifested in the speeding up of the Hα rotation, followed by enhanced mass loss not just via its famous jets at higher-than-usual speeds but also directly from its accretion disc’s wind.