GRB 970228 Within the EMBH Model

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, Edya = 5.1 × 1052 ergs, and the baryonic remnant mass MB in units of Edya, B = MBc2/Edya = 3.0 × 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 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.