  In this work, we track the evolution of an ultrarelativistic fluid onto a
Kerr black hole, on the equatorial plane. In this treatment, we consider the
limit where the rest mass density is neglected, that is, the approximation is
valid in the regime where the internal energy dominates over the rest mass
density. We particularly concentrate in the case of a gas with $\Gamma$ = 4/3,
which corresponds to a radiation fluid. We show, as in several cases, that a
shock cone appears when the asymptotic velocity of the fluid is larger than the
asymptotic relativistic sound speed of the gas. On the other hand, in order to
show the system approaches to steady state, we calculate the accreted total
energy rate on a spherical surface. Finally, we also show the gas distribution
and various of its properties.
