We study the final state of the gravitational collapse of uniformly rotating supramassive neutron stars by axisymmetric simulations in full general relativity .
The rotating stars provided as the initial condition are marginally stable against quasiradial gravitational collapse and its equatorial radius rotates with the Kepler velocity ( i.e. , the star is at the mass-shedding limit ) .
To model the neutron stars , we adopt the polytropic equations of state for a wide range of the polytropic index as n = 2 / 3 , 4/5 , 1 , 3/2 and 2 .
We follow the formation and evolution of the black holes , and show that irrespective of the value of n~ { } ( 2 / 3 \leq n \leq 2 ) , the final state is a Kerr black hole and the disk mass is very small ( < 10 ^ { -3 } of the initial stellar mass ) .