The spectral evolution of classical gamma-ray bursts

Gamma ray burst spectral evolution is characterized by two trends: on time scales of ∼ 1 s the hardness and intensity rise and fall together, but there is hard-to-soft evolution within and between intensity spikes. The major issues in the study of spectral evolution are the universality of this characterization, and whether the observed broad-band spectra are truly broad-band or whether they consist of many short-lived narrow-band (e.g., black body) flares. We present results from techniques which sacrifice spectral resolution for temporal resolution.