Peculiar nature of hard X-ray eclipse in SS433 from INTEGRAL observations

Abstract

The analysis of INTEGRAL observations (2003-2008) of superaccreting galactic microquasar SS433 at precessional phases with the maximum disk opening angle is carried out. The shape and width of the primary X-ray eclipse is found to be strongly variable suggesting additional absorption in dense stellar wind and gas outflows from the optical A7I-component. The joint modeling of X-ray eclipse and precessional X-ray variability by a geometrical model suggests the binary mass ratio q=m_x/m_v=0.3, allowing an explnation of peculiarities of the optical variability of SS433, in particular, the substantial precessional variability at the primary optical eclipse minimum. For the mass function of the optical star f_v=0.268 M_\odot as derived from Hillwig and Gies (2008) data, the obtained q yields the masses of the components m_x=5 M_\odot, m_v=15 M_\odot, confirming the black hole nature of the relativistic object in SS433. The independence of the observed hard X-ray spectrum on the precession phase suggests that hard X-ray emission is formed in an extended hot corona. The Monte-Carlo simulations of the broadband X-ray spectrum of SS433 at the maximum disk opening precessional phases allowed us to determine physical parameters of the corona (temperature T_{cor}=20 keV, Thomson optical depth τ=0.2), and to estimate the jet mass outflow rate \dot M_j=3\times 10^{19} g/s yielding the kinetic power of the jets \sim 10^{39} erg/s.