Numerical and analytical solutions of Neutrino-Dominated Accretion Flows with a Non-Zero Torque Boundary Condition and its applications in Gamma-ray Bursts

TL;DR

This paper develops numerical and analytical models of neutrino-dominated accretion flows with non-zero boundary torque, demonstrating their potential to power bright gamma-ray bursts and explaining observed variability and afterglow features.

Contribution

It introduces the first solutions for NDAFs with non-zero boundary stresses, challenging previous assumptions and expanding understanding of GRB central engines.

Findings

NDAFs with boundary torque can power bright GRBs.

Disk becomes viscously unstable, explaining GRB variability.

Boundary torque has negligible effect on gravitational wave strength.

Abstract

A stellar mass black hole (BH) surrounded by a neutrino-dominated accretion flow (NDAF) has been discussed in a number of works as the central engine of gamma-ray bursts (GRBs). It is widely believed that NDAF cannot liberate enough energy for bright GRBs. However, these works have been based on the assumption of "no torque" boundary condition, which is invalid when the disk is magnetized. In this paper, we present both numerical and analytical solutions for NDAFs with non-zero boundary stresses, and reexamine their properties. We find that NDAF with such boundary torque can be powerful enough to account for those bright short GRBs, energetic long GRBs and ultra-long GRBs. The disk becomes viscously unstable, which makes it possible to interpret the variability of GRB prompt emission and the steep decay phase in the early X-ray afterglow. Finally, we study the gravitational waves radiated from a processing BH-NDAF. We find that the effects of the boundary torque on the strength of the gravitational waves can be ignored.