GAMMA-RAY BURST PEAK DURATION AS A FUNCTION OF ENERGY

Gamma-ray burst time histories often consist of many peaks. These peak s tend to be narrower at higher energy. If gamma-ray bursts are cosmol ogical, the energy dependence of gamma-ray burst timescales must be un derstood in order to correct the timescale dependence due to the expan sion of the universe. By using the average autocorrelation function an d the average pulse width, we show that the narrowing with energy foll ows, quite well, a power law. The power-law index is similar to-0.4. T his is the first quantitative relationship between temporal and spectr al structure in gamma-ray bursts. It is unclear what physics causes th is relationship. The average autocorrelation has a universal shape suc h that one energy range scales linearly with time into all other energ y ranges. This shape is approximately the sum of two exponentials.