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The joint X and gamma-ray observations of GRB 090618 by a large number ofsatellites offer an unprecedented possibility of testing crucial aspects oftheoretical models. In particular, it allows us to test (a) the formation of anoptically thick e+e- baryon plasma self-accelerating to Lorentz factors in therange 200 < g < 3000; (b) its transparency condition with the emission of acomponent of 10^{53-54} baryons in the TeV region and (c) the collision ofthese baryons with the circumburst medium clouds, characterized by dimensionsof 10^{15-16} cm. In addition, these observations offer the possibility oftesting a new understanding of the thermal and power-law components in theearly phase of this GRB. We test the fireshell model of GRBs in one of theclosest (z = 0.54) and most energetic (Eiso = 2.90 x 10^{53} ergs) GRBs, namelyGRB 090618. We analyze its emission using several spectral models, with specialattention to the thermal and power-law components. We determine the fundamentalparameters of a canonical GRB within the context of the fireshell model. Wefind evidences of the existence of two different episodes in GRB 090618. Thefirst episode lasts 50 s and is characterized by a spectrum consisting ofthermal component, which evolves between kT = 54 keV and kT = 12 keV. Thesecond episode, which lasts for \sim 100s, behaves as a canonical long GRB witha Lorentz gamma factor at transparency of g = 495, a temperature attransparency of 29.22 keV and with characteristic masses of the surroundingclouds of \sim 10^{22-24} g. We support the recently proposed two-componentnature of GRB 090618 by using specific theoretical analysis and illustrate thatthe episode 1 cannot be considered to be either a GRB or a part of a GRB event,but it appears to be related to the progenitor of the collapsing bare coreleading to the formation of the black hole which we call a proto-black hole.

A double component in GRB 090618: a proto-black hole and a genuinely long GRB