Black hole spin dependence of general relativistic multi-transonic accretion close to the horizon

• We study the multi-transonic properties of accretion flow in Kerr metric.
• Novel perturbation scheme is introduced to study the flow stability.
• Properties of accretion flow very close to the event horizon are studied.
• The possibility of black hole shadow imaging using our flow profile is discussed.

We introduce a novel formalism to investigate the role of the spin angular momentum of astrophysical black holes in influencing the behavior of low angular momentum general relativistic accretion. We propose a metric independent analysis of axisymmetric general relativistic flow, and consequently formulate the space and time dependent equations describing the general relativistic hydrodynamic accretion flow in the Kerr metric. The associated stationary critical solutions for such flow equations are provided and the stability of the stationary transonic configuration is examined using an elegant linear perturbation technique. We examine the properties of infalling material for both prograde and retrograde accretion as a function of the Kerr parameter at extremely close proximity to the event horizon. Our formalism can be used to identify a new spectral signature of black hole spin, and has the potential of performing the black hole shadow imaging corresponding to the low angular momentum accretion flow.