We consider the gamma-ray burst of 1997 February 28 ( GRB 970228 ) within the ElectroMagnetic Black Hole ( EMBH ) model .
We first determine the value of the two free parameters that characterize energetically the GRB phenomenon in the EMBH model , that is to say the dyadosphere energy , E _ { dya } = 5.1 \times 10 ^ { 52 } ergs , and the baryonic remnant mass M _ { B } in units of E _ { dya } , B = M _ { B } c ^ { 2 } / E _ { dya } = 3.0 \times 10 ^ { -3 } .
Having in this way estimated the energy emitted during the beam-target phase , we evaluate the role of the InterStellar Medium ( ISM ) number density ( n _ { ISM } ) and of the ratio { \cal R } between the effective emitting area and the total surface area of the GRB source , in reproducing the observed profiles of the GRB 970228 prompt emission and X-ray ( 2-10 keV energy band ) afterglow .
The importance of the ISM distribution three-dimensional treatment around the central black hole is also stressed in this analysis .