1996/04/26 by Thierry Foglizzo, Foglizzo, Thierry, Maximilian Ruffert +1
Physics and Astronomy · #Astrophysics (astro-ph) #FOS: Physical sciences #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9604160
22 pages, A&A LaTeX, submitted to A&A
arxiv created 1996/04/26 · arxiv updated 2009/12/01
We prove that the sonic surface of axisymmetric meridional stationary flows is always attached to the accretor, however small, if the adiabatic index of the gas is gamma=5/3. Using local expansions near a point-like accretor, we extend Bondi's classification of spherically symmetric flows to axisymmetric flows, introducing the possibility of angular sectors reached by no flow lines, and singular directions of infinite mass flux, in addition to the angular regions of subsonic and supersonic accretion. For gamma<5/3, we show the impossibility of subsonic accretion onto a point-like accretor when the entropy of the flow is not uniform. The special case gamma=5/3 is treated separately. We analyse the influence of the adiabatic index and Mach number of the flow at infinity on the mass accretion rate of shocked spherical flows. We propose an interpolation formula for the mass accretion rate of axisymmetric flows as a function of the Mach number and the adiabatic index, in the range 9/7<gamma<5/3.