1. 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
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 J , 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.