Konwersatorium im. Leopolda Infelda

We compare Newtonian and general relativistic descriptions of thestationary accretion of selfgravitating fluids onto compact bodies.Spherical symmetry and thin gas approximation are assumed. Luminositydepends, amongst other factors, on the temperature and thecontribution of gas to the total mass, in both -- general relativistic($L_{GR}$) and Newtonian ($L_N$) -- models. We discover a remarkableuniversal behaviour for supersonic flows: the ratio of respectiveluminosities $L_{GR}/L_N$ is independent of the fractional mass of thegas and depends on asymptotic temperature. It is close to 1 in theregime of low asymptotic temperatures and can grow by one order for hightemperatures. These conclusions are valid for a wide range of polytropicequations of state.