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

TL;DR

This paper models the vertical structure of neutrino-dominated accretion disks in gamma-ray bursts, revealing how nuclear composition varies with accretion rate and potentially explains supernova light curve features.

Contribution

It presents a detailed analysis of the vertical nuclear composition of accretion disks, highlighting the dependence on accretion rate and temperature distribution, which was not previously characterized.

Findings

Heavy nuclei form near the disk surface.

Low accretion rates favor $^{56}$Ni dominance.

High accretion rates favor $^{56}$Fe dominance.

Abstract

We investigate the vertical structure and elements distribution of neutrino-dominated accretion flows around black holes in spherical coordinates with the reasonable nuclear statistical equilibrium. According 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 the vertical distribution of temperature and density. In this thin region, we find that $^{56}\rm Ni$ is dominant for the flow with low accretion rate (e.g., $0.05 $$M_{\odot}$ $\rm s^{-1}$) but $^{56}\rm Fe$ is dominant for the high counterpart (e.g., $1 M_{\odot}$ $\rm s^{-1}$). The dominant $^{56}\rm Ni$ in the special region may provide a clue to understand the bumps in the optical light curve of core-collapse supernovae.