Slow Heating Model of Gamma-Ray Burst: Photon Spectrum and Delayed Emission

We propose a new mechanism for the prompt emission of gamma-ray burst. In our model electrons are continuously accelerated in the post shock region via plasma turbulance. Using Monte Carlo technique, we mimic the 2 order Fermi acceleraion due to plasma turbulance and obtain photon spectra. Since the acceleration balances with the synchrotron cooling, the observed low-energy spectral index is naturally explained. The resultant spectra can be consistent with observed spectra at least below ∼ 1 MeV. The model also predicts delayed GeV-TeV emission due to inverse Compton and broad pulse profile of optical emission in some cases. Although nontrivial assumptions are required to reproduce MeV-GeV power-law spectra, the model implies the possibility to explain various kinds of luminosity correlations. Subject headings: gamma rays: bursts — gamma rays: theory — radiation mechanisms: nonthermal — cosmic rays