Evidence for chromatic X-ray light-curve breaks in Swift gamma-ray burst afterglows and their theoretical implications

摘要: The power-law decay of the X-ray emission gamma-ray burst (GRB) afterglows 050319, 050401, 050607, 050713A, 050802 and 050922C exhibits a steepening at about 1-4 h after which, surprisingly, is not accompanied by break in optical emission. If it assumed that both arise from same outflow then, framework standard forward shock model, chromaticity light-curve breaks indicates they do solely mechanism related to dynamics (e.g. energy injection) or angular distribution blast-wave kinetic (structured outflows jets). lack spectral evolution accompanying shows these passage cooling frequency) either. Under circumstances, decoupling decays requires microphysical parameters for electron magnetic energies evolve time, whether afterglow synchrotron inverse-Compton For steady with Lorentz factor an light curve arising cessation injection into blast wave, properties above six Swift require circumburst medium r -2 radial stratification, as expected massive star origin long GRBs. Alternatively, chromatic may indicate emissions different outflows. Neither feature (evolution emissions) was clearly required pre-Swift afterglows.