A NuSTAR view of SS433. Precessional evolution of the jet-disk system

Context. SS433 is a Galactic microquasar with powerful outflows (double jet, accretion disk and winds) with a well-known orbital, precessional, and nutational period.
Aims: In this work we characterise different outflow parameters throughout the precessional cycle of the system.
Methods: We analysed ten NuSTAR (3-70 keV) observations of ∼30 ks that span ∼1.5 precessional cycles. We extracted averaged spectra and modelled them using a combination of a double thermal jet model (bjet) and pure neutral and relativistic reflection (xillverCp and relxilllpCp) over an accretion disk.
Results: We find an average jet bulk velocity of β = v/c ∼ 0.29 with an opening angle of ≲6 deg. Eastern jet kinetic power ranges from 1 to 10³⁹ erg s⁻¹, with base `coronal' temperatures T_o ranging from between 14 and 18 keV. Nickel-to-iron abundances remain constant at ∼9 (within 1σ). The western to eastern jet-flux ratio becomes ∼1 on intermediate phases, which is about 35% of the total precessional orbit. The 3-70 keV total unabsorbed luminosity of the jet and disk ranges from 2 to 20 × 10³⁷ erg s⁻¹, with the disk reflection component mainly contributing to the hard 20-30 keV excess and the stationary 6.7 keV ionised Fe line complex.
Conclusions: At low opening angles Θ, we find that the jet expands sideways following an adiabatic expansion of a gas with temperature T_o. Finally, the central source and lower parts of the jet could be hidden by an optically thick region of τ > 0.1 and size R ∼ N_H/n_e0 ∼ 1.5 × 10⁹ cm ∼ 1700 r_g for M_BH = 3 M_⊙.