How Temporal Symmetry Defines Morphology in BATSE Gamma-Ray Burst Pulse Light Curves

We present compelling evidence that most gamma-ray burst (GRB) pulse light curves can be characterized by a smooth single-peaked component coupled with more complex emission structure is temporally symmetric around the time of peak. The model successfully fits 86% Burst and Transient Source Experiment GRB pulses bright enough for structural properties to measured. Surprisingly, pulse's light-curve morphology accurately predicted asymmetry stretching/compression needed align components preceding temporal mirror time-reversed following it. Such prediction only possible because exhibit symmetry. Time-asymmetric include fast rise exponential decays, rollercoaster pulses, asymmetric u-pulses, while time-symmetric u-pulses crowns. Each morphological type specific asymmetries, stretching parameters, durations, alignments between structured components, delineation in asymmetry/stretching distribution suggests may belong separate populations. Furthermore, belonging short class similar morphologies long class, but appear simply occur on shorter timescales.