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Accepted · first revision · record

Title: What radiation mechanism produces GRB prompt gamma-ray spectra?
Plain: The first seconds of gamma rays have a spectral shape that neither the glow of hot gas nor electrons spiraling in magnetic fields (synchrotron radiation) reproduces cleanly.
Precise: Explain the prompt spectra (peak energy $E_p \sim 100\,\mathrm{keV}$ to a few MeV; low-energy photon index $\alpha \sim -1$, harder than the fast-cooling synchrotron value $-3/2$, with a sizable fraction of spectra harder than the slow-cooling synchrotron limit $-2/3$) and the $E_p$ versus isotropic energy (Amati) correlation, choosing among synchrotron from internal shocks or reconnection with marginally fast cooling, dissipative photospheres, and Comptonization. Answer: a mechanism and dissipation radius that reproduce spectra, variability and correlations for a large sample.
Settled by: Joint fits of time-resolved spectra and polarization of a large burst sample by one mechanism with physically consistent parameters.
Kind: phenomenon
Answer type: mechanism
References: (empty)
Literature status: contested
Status note: (empty)
Posed since: (empty)