  In strict analogy to prompt pulses, X-ray flares observed by Swift-XRT in
long Gamma-Ray Bursts define a lag-luminosity relation: L_p,iso \propto
t_lag^{-0.95+/-0.23}. The lag-luminosity is proven to be a fundamental law
extending 5 decades in time and 5 in energy. This is direct evidence that GRB
X-ray flares and prompt gamma-ray pulses are produced by the same mechanism.

High Energy Astrophysical Phenomena