We discuss how the annihilation luminosity of a neutrino-cooled accretion disk in a gamma-ray burst, $ L_{V\bar V} $ , is determined by the disk’s fundamental parameters, namely, the mass of the central black hole M,...We discuss how the annihilation luminosity of a neutrino-cooled accretion disk in a gamma-ray burst, $ L_{V\bar V} $ , is determined by the disk’s fundamental parameters, namely, the mass of the central black hole M, the mass accretion rate ?, and the viscosity parameter α. It is shown that $ L_{V\bar V} $ depends mainly on ? in evidence, and decreases with increasing M, but is almost independent of α. This result argues additionally that the central black hole in a gamma-ray burst must be with a stellar mass.展开更多
The inconsistency of the energy equation used in the literature is pointed out and a new consistent energy equation is given. With this new energy equation, calculations are made for the limit-cycle behaviors of therm...The inconsistency of the energy equation used in the literature is pointed out and a new consistent energy equation is given. With this new energy equation, calculations are made for the limit-cycle behaviors of thermally unstable accretion disks around black holes. From the comparison of our numerical results with those obtained using the inconsistent energy equation, it is found that the inconsistent energy equation undervalues the temperature and overvalues the effective optical depth when the accreted gas becomes effectively optically thin. Thus, it is dangerous if the inconsistent energy equation is used in the studies of very hot and optically thin accretion flows such as advection-dominated accretion flows (ADAFs), and our new energy equation is likely to be a better alternative.展开更多
基金Supported by the National Basic Research Program of China (Grant No. 2009CB824800)the National Natural Science Foundation of China (Grant Nos. 10673009 and 10833002)
文摘We discuss how the annihilation luminosity of a neutrino-cooled accretion disk in a gamma-ray burst, $ L_{V\bar V} $ , is determined by the disk’s fundamental parameters, namely, the mass of the central black hole M, the mass accretion rate ?, and the viscosity parameter α. It is shown that $ L_{V\bar V} $ depends mainly on ? in evidence, and decreases with increasing M, but is almost independent of α. This result argues additionally that the central black hole in a gamma-ray burst must be with a stellar mass.
基金Supported by the National Basic Research Program of China (Grant No.2009CB824800)the National Natural Science Foundation of China (Grant Nos.10673009 and 10833002)the Natural Science Foundation of Fujian Province of China (Grant No.V0750001)
文摘The inconsistency of the energy equation used in the literature is pointed out and a new consistent energy equation is given. With this new energy equation, calculations are made for the limit-cycle behaviors of thermally unstable accretion disks around black holes. From the comparison of our numerical results with those obtained using the inconsistent energy equation, it is found that the inconsistent energy equation undervalues the temperature and overvalues the effective optical depth when the accreted gas becomes effectively optically thin. Thus, it is dangerous if the inconsistent energy equation is used in the studies of very hot and optically thin accretion flows such as advection-dominated accretion flows (ADAFs), and our new energy equation is likely to be a better alternative.
