Unstable e± photospheres and GRB spectral relations

Kunihito Ioka, Kohta Murase, Kenji Toma, Shigehiro Nagataki, Takashi Nakamura, Peter Mészáros

Research output: Chapter in Book/Report/Conference proceedingConference contribution


We propose an emission mechanism of prompt gamma-ray bursts (GRBs) that can reproduce the observed nonthermal spectra with high radiative efficiencies, >50%. We show that, if e± pairs outnumber protons, a radiation-dominated photosphere becomes unstable to the phase separation between pairs and proton clumps. Pairs are continuously shock heated by proton clumps, scattering the thermal photons into the observed broken power-law shape. If GRBs come from pair photospheres, pair annihilation lines are predicted above continua. A closure relation exists between the pair annihilation line and the pair creation cutoff, which enables GLAST to test the model and also constrain physical quantities such as the Lorentz factor, optical depth and pair-to-baryon ratio, only from observables, even without either line or cutoff. We also discuss the Suzaku/WAM results of the time-resolved Ep-L (Yonetoku) relation and the Ep-L relation for short GRBs. We suggest that the short GRBs could arise from the self-created photospheres. We also deal with the hypernova and GRB remnants emitting TeV gamma-rays via the decay of accelerated radioactive isotopes, such as 56Co conveyed by the GRB jets.

Original languageEnglish
Title of host publication2008 Nanjing Gamma-Ray Burst Conference
Number of pages6
Publication statusPublished - 2008
Externally publishedYes
Event2008 Nanjing Gamma-Ray Burst Conference - Nanjing, China
Duration: 2008 Jun 232008 Jun 27

Publication series

NameAIP Conference Proceedings
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616


Conference2008 Nanjing Gamma-Ray Burst Conference


  • Gamma rays: bursts
  • Gamma rays: theory
  • Radiation mechanism: non-thermal

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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