ИСТИНА

The report was devoted the observations og microquasar SS 433 and was based on multiyear INTEGRAL observations of SS433 in 2003-2011. A composite IBIS/ISGRI 18-60 keV orbital light curve was constructed around zero precessional phases psipr = 0 at the maximum accretion disc opening angle. It showed a peculiar shape with significant excess near the orbital phase phiorb = 0.25, which was not seen in the softer 2-10 keV energy band. The 40-60 keV orbital light curve demonstrated two almost equal humps at phases ˜0.25 and ˜0.75, most likely due to nutation effects of the accretion disc. The nutational variability of SS433 in 15-50 keV with a period of ~6.290 d was independently found from analysis of Swift/Burst Alert Telescope data. The change of the off-eclipse 18-60 keV X-ray flux with the precessional phase showed a double-wave form with strong primary maximum at psipr = 0 and weak but significant secondary maximum at psipr = 0.6. A weak variability of the 18-60 keV flux in the middle of the orbital eclipse correlated with the disc precessional phase was also observed. The joint analysis of the broad-band 18-60 keV orbital and precessional light curves confirmed the presence of a hot extended corona in the central parts of the supercritical accretion disc and constrains the binary mass ratio in SS433 in the range 0.5 ≳ q ≳ 0.3, suggesting the black hole nature of the compact object.