  In this paper, we discuss a two-dimensional numerical study of isothermal
high Mach number Bondi--Hoyle--Lyttleton flow around a small accretor. The flow
is found to be unstable at high Mach numbers, with the instability appearing
even for a larger accretor. The instability appears to be the unstable radial
mode of the accretion column predicted by earlier analytic work.
