SIMBAD references

Using GRB 991216 as a prototype, we show that the intensity substructures observed in what is generally called the ``prompt emission'' in gamma-ray bursts (GRBs) do originate in the collision between the accelerated baryonic matter pulse with inhomogeneities in the interstellar medium (ISM). The initial phase of such process occurs at a Lorentz factor γ∼310. The crossing of ISM inhomogeneities of sizes ΔR∼10¹⁵ cm occurs in a detector arrival time interval of ∼0.4 s, implying an apparent superluminal behavior of ∼10⁵c. The long-lasting debate between the validity of the external shock model versus the internal shock model for GRBs is solved in favor of the first.