A Study of the Overall Evolution Behaviors of Pulses and Flares within Gamma-Ray Bursts

Abstract

Many studies have shown that the X-ray flares in gamma-ray bursts (GRBs) have similar properties to the prompt emission pulses that occur in GRBs, suggesting that they may come from the same origin. We attempt to extend the evolution behavior that exists among GRBs to within individual GRBs. By selecting 12 GRBs with both multipulses and multiflares, we systematically study the overall evolution behaviors of the pulses and flares that occur within GRBs, including the width (w), peak time (t peak), rise time (t rise), decay time (t decay), and spectral lag. We find that correlated relationships exist within the GRBs, even if the overall evolution slopes of the pulses and flares in different GRBs are different. We also study the relations between the full pulse width (ω), the ratio of the rising width to the decay width (r/d), and the energy (E) of multipulses and multiflares within GRBs. It is found that there is a power-law anticorrelation between ω and E and a power-law correlation between r/d and E, with the mean values of the two power-law indexes being −0.42 and 0.07, respectively, which are very close to the values that are obtained for the prompt emission pulses. In addition, we find that the percentages of the positive lags for pulses and flares are 83% and 92%, respectively, with the lags of the flares being much larger than those of the pulses. Our results indicate that the overall evolution behaviors of the pulses and flares within individual GRBs are similar to the evolution behavior among GRBs, and that flares are low-energy extensions of pulses, providing further evidence that both come from the same origin.