The vertical composition of neutrino-dominated accretion disks in gamma-ray bursts

Abstract

We investigate the vertical structure and element distribution of neutrino-dominated accretion flows around black holes in spherical coordinates using the reasonable nuclear statistical equilibrium. According to our calculations, heavy nuclei tend to be produced in a thin region near the disk surface, whose mass fractions are primarily determined by the accretion rate and vertical distribution of temperature and density. In this thin region, we find that 56Ni is dominant for the flow with a low accretion rate (e.g., 0.05 M s-1), but 56Fe is dominant for the flow with a high accretion rate (e.g., 1 M s-1). The dominant 56Ni in the aforementioned region may provide a clue to understanding the bumps in the optical light curve of core-collapse supernovae. © 2013. The American Astronomical Society. All rights reserved..