Self-organized criticality in gamma-ray bursts and black holes Fa-Yin Wang and Zi-Gao Dai School of Astronomy and Space Science, Nanjing University, China (fayinwang@nju.edu.cn) X-ray flares detected in nearly half of gamma-ray-burst (GRB) afterglows are one of the most intriguing phenomena in high-energy astrophysics. But the physical mechanism of the are mysterious. We find that X-ray flares and solar flares share three statistical properties: power-law frequency distributions for energies, durations, and waiting times, which can be explained by self-organized criticality (SOC) theory. The two types of flares driven by a magnetic reconnection process. (Wang & Dai 2013, Nature Physics, 9, 465) a: The cumulative distribution of solar flares with α=-1.65. b: The differential distribution of GRB X-ray flares with α=-1.1. a: The differential distribution of solar flares with α=-2.0. b: The differential distribution of GRB X-ray flares with α=-1.0. 1 a: The differential distribution of solar flares with α=-2.0. b: The differential distribution of GRB X-ray flares with α=-1.8. X-ray flares also have been detected in the tidal disruption event Swift J1644+57, the supermassive black hole Sgr A∗ at the center of our Galaxy, and some active galactic nuclei. These flares also show power-law distributions of energies (below figure), durations, and waiting times, which can be explained by a fractal-diffusive, self-organized criticality model. (Wang, Dai, Yi & Xi, 2015, ApJS, 216, 8 ) Summary X-ray flares from different objects show similar distribution of energy, duration time and waiting times, which can be explained using SOC theory. These X-ray flares may be driven by magnetic reconnection.