Accretion of gas having specific heat ratio 4/3 by a moving gravitating body

A numerical solution is found for the flow surrounding a gravitating body moving through a gas having specific heat ratio 4/3. The gas is allowed to be accreted by the body unhindered by conditions on its surface. The results are presented for three Mach speeds 0.6, 1.5 and 3.6 representing subsonic, mildly supersonic and hypersonic flows respectively. The results are qualitatively different from the adiabatic case (specific heat ratio 5/3), reported earlier, in that the primary shock is indented, that there exists a secondary shock and that gas is accreted supersonically. These qualitative differences are expected to be present for any gas with specific heat ratio γ lying in the range 1 < γ < 5/3. The subsonic flow shows density and temperature contours very similar to those of a stationary body. In the supersonic cases there is no accretion column, the density being significantly higher immediately behind the shock than along the accretion axis, and the body is preceded by a high-density wedge of gas. For Mach speeds greater than 2 the accretion rate is at least twice the maximum value predicted by the Bondi-Hoyle-Lyttleton process. (author)