Properties of accretion flow in deformed Kerr spacetime

Abstract: We study the properties of a low-angular momentum, inviscid, advective accretion flow in a deformed Kerr spacetime under the framework of general theory of relativity. We solve the governing equations that describe the flow motion in terms of input parameters, namely energy ($E$), angular momentum ($\lambda$), spin ($a_{\rm k}$) and deformation parameter ($\varepsilon$), respectively. We find that global transonic accretion solutions continue to exist in non-Kerr spacetime. Depending on the input parameters, accretion flow is seen to experience shock transition and we find that shocked induced accretion solutions are available for a wide range of the parameter space in $\lambda-E$ plane. We examine the modification of the shock parameter space with $\varepsilon$, and find that as $\varepsilon$ is increased, the effective region of the parameter space is reduced, and gradually shifted towards the higher $\lambda$ and lower $E$ domain. In addition, for the first time in the literature, we notice that accretion flow having zero angular momentum admits shock transition when spacetime deformation is significantly large. Interestingly, beyond a critical limit of $\varepsilon^{\rm max}$, the nature of the central object alters from black hole (BH) to naked singularity (NS) and we identify $\varepsilon^{\rm max}$ as function of $a_{\rm k}$. Further, we examine the accretion solutions and its properties around the naked singularity as well. Finally, we indicate the implications of the present formalism in the context of astrophysical applications.