Self-organized criticality in multi-pulse gamma-ray bursts
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Front. Phys. 16(1), 14501 (2021)
Research article Self-organized criticality in multi-pulse gamma-ray bursts Fen Lyu1,2 , Ya-Ping Li3,† , Shu-Jin Hou4 , Jun-Jie Wei1 , Jin-Jun Geng6,7,‡ , Xue-Feng Wu1,5,# 1
Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210023, China 2 University of Chinese Academy of Sciences, Beijing 100049, China 3 Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA 4 College of Physics and Electronic Engineering, Nanyang Normal University, Nanyang 473061, China 5 School of Astronomy and Space Science, University of Science and Technology of China, Hefei 230026, China 6 School of Astronomy and Space Science, Nanjing University, Nanjing 210023, China 7 Institute of Astronomy and Astrophysics, University of Tübingen, Auf der Morgenstelle 10, D-72076, Tübingen, Germany Corresponding authors. E-mail: † [email protected], ‡ [email protected], # [email protected] Received July 21, 2020; accepted August 23, 2020
The variability in multi-pulse gamma-ray bursts (GRBs) may help to reveal the mechanism of underlying processes from the central engine. To investigate whether the self-organized criticality (SOC) phenomena exist in the prompt phase of GRBs, we statistically study the properties of GRBs with more than 3 pulses in each burst by fitting the distributions of several observed physical variables with a Markov Chain Monte Carlo approach, including the isotropic energy Eiso , the duration time T , and the peak count rate P of each pulse. Our sample consists of 454 pulses in 93 GRBs observed by the CGRO/BATSE satellite. The best-fitting values and uncertainties for these power-law indices of the +0.18 d d differential frequency distributions are: αE = 1.54±0.09, αTd = 1.82+0.14 −0.15 and αP = 2.09−0.19 , while the +0.08 c c power-law indices in the cumulative frequency distributions are: αE = 1.44−0.10 , αT = 1.75+0.11 −0.13 and c αP = 1.99+0.16 . We find that these distributions are roughly consistent with the physical framework −0.19 of a Fractal-Diffusive, Self-Organized Criticality (FD-SOC) system with the spatial dimension S = 3 and the classical diffusion β=1. Our results support that the jet responsible for the GRBs should be magnetically dominated and magnetic instabilities (e.g., kink model, or tearing-model instability) lead the GRB emission region into the SOC state. Keywords gamma-ray burst, general methods: statistical
1 Introduction Gamma-ray bursts (GRBs) are extremely energetic events occurring at the cosmological distance. The observed GRB lightcurves usually consist of several pulses characterized by highly temporal variabilities. It is well accepted that the prompt gamma-ray emission is generated by internal dissipation processes while the later afterglow is produced through the shock wave interacting with the surrounding medium. There is a consensus that long GRBs originate from the collapse of massive stars [1], while short GRBs are from mergers of two compact objects such as binary neutron stars or black hole–neutron star binar
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