On the Prompt Signals of Gamma Ray Bursts

¹ Department of Physics and Leung Center for Cosmology and Particle Astrophysics (LeCosPA), National Taiwan University, Taipei, Taiwan 10617 & KIPAC, SLAC, Stanford University, CA 94035, USA ;
e-mail: pisinchen@phys.ntu.edu.tw
² ZEST & Ludwig-Maximilians-Universitat Munchen, Fakultat f. Physik, am Coulombwall 1, 85748 Garching, Germany
³ Posthumous, Department of Physics, University of Alabama, Huntsville, AL 35899, USA

Abstract

We introduce a new model of gamma ray burst (GRB) that explains its observed prompt signals, namely, its primary quasi-thermal spectrum and high energy tail. This mechanism can be applied to either assumption of GRB progenitor: coalescence of compact objects or hypernova explosion. The key ingredients of our model are: (1) The initial stage of a GRB is in the form of a relativistic quark-gluon plasma lava; (2) The expansion and cooling of this lava results in a QCD phase transition that induces a sudden gravitational stoppage of the condensed non-relativistic baryons and form a hadrosphere; (3) Acoustic shocks and Alfven waves (magnetoquakes) that erupt in episodes from the epicenter efficiently transport the thermal energy to the hadrospheric surface and induce a rapid detachment of leptons and photons from the hadrons; (4) The detached e ⁺ e ⁻  and γ form an opaque, relativistically hot leptosphere, which expands and cools to T ~ mc², or 0.5 MeV, where e ⁺ e ⁻  → 2γ and its reverse process becomes unbalanced, and the GRB photons are finally released; (5) The mode-conversion of Alfven waves into electromagnetic waves in the leptosphere provides a snowplow acceleration and deceleration that gives rise to both the high energy spectrum of GRB and the erosion of its thermal spectrum down to a quasi-thermal distribution. According to this model, the observed GRB photons should have a redshifted peak frequency at E_p ~ Γ(1 + β/2)mc²/(1 + z), where Γ ~ O(1) is the Lorentz factor of the bulk flow of the lava, which may be determined from the existing GRB data.