Lorentz Factor-Isotropic Luminosity/Energy Correlations of GRBS and Their Interpretation

• Published in: arXiv.org 2012-03
• Main Authors: Lv, Jing, Zou, Yuan-Chuan, Wei-Hua, Lei, Zhang, Bing, Qing-Wen, Wu, Ding-Xiong, Wang, En-Wei, Liang, Hou-Jun Lv
• Format: Article
• Language: English
• Subjects: Accretion disks; Black holes; Correlation; Ejecta; Gamma ray bursts; Gamma rays; Lorentz factor; Luminosity; Neutrinos; Stellar mass; Stellar mass accretion; Stellar winds
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1109.3757

The bulk Lorentz factor of the gamma-ray burst (GRB) ejecta (Gamma_0) is a key parameter to understand the GRB physics. Liang et al. have discovered a correlation between Gamma_0 and isotropic gamma-ray energy: Gamma_0\proptoE_{gamma,iso,52}^{0.25}. By including more GRBs with updated data and more methods to derive Gamma_0, we confirm this correlation and obtain Gamma_0~91E_{gamma,iso,52}^{0.29}. Evaluating the mean isotropic gamma-ray luminosities L_{gamma,iso} of the GRBs in the same sample, we discover an even tighter correlation Gamma_0~249 L_{gamma,iso,52}^{0.30}. We propose an interpretation to this later correlation. Invoking a neutrino-cooled hyperaccretion disk around a stellar mass black hole as the central engine of GRBs, we derive jet luminosity powered by neutrino annihilation and baryon loading from a neutrino-driven wind. Applying beaming correction, we finally derive Gamma_0\proptoL_{gamma,iso}^{0.22}, which is well consistent with the data. This suggests that the central engine of long GRBs is likely a stellar mass black hole surrounded by a hyper-accreting disk.