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The temporal and spectral analysis of nine bright X-ray flares out of a sample of 113 flares observed by Swift reveals that the flare phenomenology is strictly analogous to the prompt γ-ray emission: high-energy flare profiles rise faster, decay faster and peak before the low-energy emission. However, flares and prompt pulses differ in one crucial aspect: flares evolve with time. As time proceeds, flares become wider, with larger peak lag, lower luminosities and softer emission. The flare spectral peak energy evolves to lower values following an exponential decay which tracks the decay of the flare flux. The two flares with best statistics show higher than expected isotropic energy and peak luminosity when compared to the and prompt correlations. is found to correlate with within single flares, giving rise to a time-resolved . Like prompt pulses, flares define a lag–luminosity relation: . The lag–luminosity is proven to be a fundamental law extending ∼5 decades in time and ∼5 decades in energy. Moreover, this is direct evidence that γ-ray burst (GRB) X-ray flares and prompt γ-ray pulses are produced by the same mechanism. Finally we establish a flare–afterglow morphology connection: flares are preferentially detected superimposed to one-break or canonical X-ray afterglows. [ABSTRACT FROM AUTHOR]

GRB 080503 was classified as a short gamma-ray burst (GRB) with extended emission. The origin of such extended emission (found in about a quarter of Swift short GRBs) is still unclear and may provide some clues to the identity of the elusive progenitors of short GRBs. The extended emission from GRB 080503 is followed by a rapid decay phase (RDP) that is detected over an unusually large dynamical range (one decade in time and decades in flux), making it ideal for studying the nature of the extended emission from short GRBs. We model the broad envelope of extended emission and the subsequent RDP using a physical model for the prompt GRB emission and its high latitude emission tail, in which the prompt emission (and its tail) is the sum of its individual pulses (and their tails). For GRB 080503, a single pulse fit is found to be unacceptable, even when ignoring short time-scale variability. The RDP displays very strong spectral evolution and shows some evidence for the presence of two spectral components with different temporal behaviour, likely arising from distinct physical regions. A two pulse fit (a first pulse accounting for the gamma-ray extended emission and decay phase, and the second pulse accounting mostly for the X-ray decay phase) provides a much better (though not perfect) fit to the data. The shallow gamma-ray and steep hard X-ray decays are hard to account for simultaneously, and require the second pulse to deviate from the simplest version of the model we use. Therefore, while high latitude emission is a viable explanation for the RDP in GRB 080503, it does not pass our tests with flying colours, and it is quite plausible that another mechanism is at work here. Finally, we note that the properties of the RDP following the extended emission of short GRBs (keeping in mind the very small number of well-studied cases so far) appear to have different properties than that following the prompt emission of long GRBs. However, a larger sample of short GRBs with extended emission is required before any strong conclusion can be drawn. [ABSTRACT FROM AUTHOR]