Relativistic Flows in Astrophysics

Abstract

Most of the matter accreting onto a compact object, or emanating from its vicinity, can be satisfactorily modeled as a fluid. These fluids are different from terrestrial versions. The temperature can range from relativistic values to non-relativistic ones and at high temperature, the fluid is composed of charges and not neutral particles as is the case in the terrestrial version.

We use relativistic equation of state to describe trans-relativistic fluid, around compact objects and at regions far from it. For steady state investigation we took the help of generalized Bernoulli parameter which acts as a constant of motion. We also exploited the fact that the global solution should be of higher entropy and correct boundary conditions. This approach is considered for dissipative accretion flow in curved geometry around black holes, magnetosphere around neutron stars or white dwarfs, and also for magnetically driven outflows. We show that the flow geometry close to a black hole is quite different from a neutron star because of the strong magnetic field around the latter, which has implication on the radiative processes dominant nearby. We also obtained shock solutions for lepton dominated accretion flow around neutron stars, but not around black holes, this is again due to the different flow geometry around the two different types of compact objects. Magnetically driven flows in the special relativistic domain, are able to produce flows which connect both the Alfven and fast sonic points. Numerical simulation of the fluid with relativistic equation of state, shows distinct differences depending on the composition of the flow.