Transonicity in a spherically symmetric accreting system has been considered
in both the stationary and the dynamic regimes. The stationary flow, set up as
a dynamical system, has been shown to be greatly unstable to even the minutest
possible deviation in the boundary condition for transonicity. With the help of
a simple analytical model, and some numerical modelling, it has then been
argued that the flow indeed becomes transonic and stable, when the evolution of
the flow is followed through time. The time-dependent approach also shows that
there is a remarkable closeness between an equation of motion for a
perturbation in the flow, and the metric of an analog acoustic black hole.Comment: 13 pages, 7 figures, REVTeX. This article is an invited contribution
to a special issue of the Indian Journal of Physics, dedicated to the revered
memory of Prof. Amal Kumar Raychaudhur
