A New Model for Iron Emission Lines and Re-Burst in GRB X-Ray Afterglows

摘要

Recently iron emission features have been observed in several X-rayafterglows of GRBs. It is found that the energy obtained from the illuminatingcontinuum which produces the emission lines is much higher than that of themain burst.The observation of SN-GRB association indicates a fallback diskshould be formed after the supernovae explosion. The disk is optically thickand advection-dominated and dense. We suggest that the delayed injection energyafter the initial main burst, much higher than energy of the main burst, causesthe re-burst appearance in GRB afterglow and illuminates the region of the disksurface with $aupprox1$($au$ is the optical depth for the Thomson scatter) and produces the iron emission line whose luminosity can be up to $10^{45}$erg$s^{-1}$. The duration of the iron line emission can be $10^{4}-10^{5}$ s.This model can explain the appearance of re-burst and emission lines in GRBafterglow and disappearance of the iron emission lines, and also can naturallysolve the problem of higher energy of the illuminating continuum than that ofthe main burst. This scenario is different from the models put forward toexplain the emission lines before, that can be tested by SWIFT satellite.