ИСТИНА

SS433 is a unique Galactic steadily superaccreting microquasar with mildly relativistic ($v=0.26 c$), precessing jets. This massive X-ray binary system at advanced evolutionary stage exhibits three photometric and spectral periodicities related to the precession ($P_{pr}\simeq 162.5$~d), orbital ($P_{orb}\simeq 13.082$~d) and nutation ($P_{nut}\simeq 6.29$~d) periods, which are found to be stable during an observational time of more than 30 years. Multiyear INTEGRAL observations of SS433 performed in 2003-2011 allowed us to construct composite IBIS/ISGRI orbital, precessional and nutational light curves of this unique object. The joint analysis of the broad-band 18-60~keV orbital and precessional light curves suggests the presence of a hot extended corona around the precessing supercritical accretion disk. This analysis allows us to constrain the binary mass ratio in SS433 in the range $q=m_x/m_v=0.3\div 0.5$ suggesting the black hole nature of the compact object.