Region of the Anomalous Compression in the Bondi-hoyle Accretion

Properties of a gas flow in the axisymmetric case with zero angular momentum in the supersonic region is explored for accretion onto a small compact object, in particular, onto Schwarzschild black hole when the velocity of the object is less than the sound velocity at infinity. First, it is shown that for ballistic flow, i.e. for zero pressure gradient, flow lines intersection occurs in the front part of the object at some distance rx from the center at the symmetry axis of the system (caustic formates). Specific radial size of the region where flow lines emerged with angle not exceeding θ0 from the sound surface intersect themselves is about ∆r = rxθ 2 0 /3. Then the numerical calculation for nonzero pressure gradient is carried out for the detailed elaboration of the flow structure (adiabatic flow is assumed). Estimation of parameters of the region with anomalously high temperature and matter density is made; this compression is accompanied by anomalously high energy release.