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We show that γ-ray burst (GRB) afterglow observations strongly suggest, within the fireball model framework, that radiating electrons are shock accelerated to a power-law energy distribution, dn e /dγ e ∝ γ −p e , with universal index p ≈ 2.2, and that the fraction of shock energy carried by electrons, ξ e , is universal and close to equipartition, ξ e ∼(More)
Massive stars end their short lives in spectacular explosions--supernovae--that synthesize new elements and drive galaxy evolution. Historically, supernovae were discovered mainly through their 'delayed' optical light (some days after the burst of neutrinos that marks the actual event), preventing observations in the first moments following the explosion.(More)
We argue that the observed correlation between the radio luminosity and the X-ray luminosity in radio emitting galaxy clusters implies that the radio emission is due to secondary electrons that are produced by p-p interactions and lose their energy by emitting synchrotron radiation in a strong magnetic field, B > (8πaT 4 CMB) 1/2 ≃ 3 µG. We construct a(More)
A pedagogical derivation is presented of the " fireball " model of γ-ray bursts, according to which the observable effects are due to the dissipation of the kinetic energy of a relativistically expanding wind, a " fireball. " The main open questions are emphasized, and key afterglow observations, that provide support for this model, are briefly discussed.(More)
Electromagnetic (and adiabatic) energy losses of pi's and mu's modify the flavor ratio (measured at Earth) of neutrinos produced by pi decay in astrophysical sources, Phi v: phi v mu: phi v tau, from 1:1:1 at low energy to 1:1.8:1.8 at high energy. The transition occurs over 1-2 decades of v energy, and is correlated with a modification of the neutrino(More)