Global solution of viscous accretion disk around rotating compact objects: a pseudo-general-relativistic study

We study the solution of viscous accretion disks around rotating compact/central object having hard surface i.e. neutron star, strange star and any other highly gravitating objects. We choose pseudo-Newtonian approach to describe the relativistic accretion disk. For this purpose, the new pseudo-Newtonian potential is used which is applicable to describe the relativistic properties of star and its disk. As we know, the Hartle-Thorne metric can describe geometry of star as well as the space-time out-side of it, we use this metric for our study. This potential reproduces the marginally stable orbit exactly as that of general relativity. It also reproduces the marginally bound orbit and specific mechanical energy at the marginally stable orbit with at most 4% and 10% error respectively. Using this potential we study the global parameter space of the accretion disk. Thus, we find out the physical parameter regime, for which the stable accretion disk can be formed around gravitating object with hard surface. We show that with the change of rotation to the central object, the valid disk parameter region dramatically changes. We also show the effect of viscosity to the fluid properties of the disk. Subsequently, we give a theoretical prediction of kHz QPO, at least for one out of a pair, for a fast rotating compact object as 4U 1636-53.