Download or read book Wind Accretion Onto Compact Objects written by Ileyk El Mellah and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: X-ray emission associated to accretion onto compact objects displays important levels of photometric and spectroscopic time-variability. When the accretor orbits a Supergiant star, it captures a fraction of the supersonic radiatively-driven wind which forms shocks in its vicinity. The amplitude and stability of this gravitational beaming of the flow conditions the mass accretion rate responsible, in fine, for the X-ray luminosity of those Supergiant X-ray Binaries (SgXB). The capacity of this low angular momentum inflow to form a disc susceptible to be the stage of instabilities remains at stake.Using state-of-the-art numerical setups, we characterize the structure of a Bondi-Hoyle- Lyttleton flow onto a compact object, from the shock down to the vicinity of the accretor, typically five orders of magnitude smaller. The evolution of the bow shock which forms around the accretor (transverse structure, opening angle, stability, temperature profile...) with the Mach number of the flow is detailed. The robustness of those simulations based on the High Performance Computing MPI-AMRVAC code is supported by the topology of the inner sonic surface, consistent with theoretical expectations.We develop a synthetic model of mass transfer in SgXB which couples the launching of the wind the stellar parameters, the orbital evolution of the streamlines and the accretion process. We show that the shape of the permanent flow is entirely determined by the filling and Eddington factor, the mass ratio and the alpha force multiplier. Provided scales are known, we can trace back, eg, the X-ray luminosity, the accretion mechanism (stream or wind-dominated) and the shearing of the inflow.