Magnetically Torqued Neutrino-Dominated Accretion Flows for Gamma-ray Bursts

TL;DR

This paper explores how magnetic coupling in neutrino-dominated accretion flows around Kerr black holes can enhance gamma-ray burst luminosity and induce instability, potentially explaining observed GRB variability and X-ray flares.

Contribution

It introduces the effects of magnetic torque on NDAFs, showing how it increases luminosity and causes instability, offering new insights into GRB central engine behavior.

Findings

Magnetic torque significantly boosts neutrino annihilation luminosity.

Inner disk becomes thermally and viscously unstable due to magnetic effects.

Magnetically torqued NDAF can explain GRB variability and X-ray flares.

Abstract

Recent observations and theoretical work on gamma-ray bursts (GRBs) favor the central engine model of a Kerr black hole (BH) surrounded by a magnetized neutrino-dominated accretion flow (NDAF). The magnetic coupling between the BH and disk through a large-scale closed magnetic field exerts a torque on the disk, and transports the rotational energy from the BH to the disk. We investigate the properties of the NDAF with this magnetic torque. For a rapid spinning BH, the magnetic torque transfers enormous rotational energy from BH into the inner disk. There are two consequences: (i) the luminosity of neutrino annihilation is greatly augmented; (ii) the disk becomes thermally and viscously unstable in the inner region, and behaves S-Shape of the surface density versus accretion rate. It turns out that magnetically torqued NDAF can be invoked to interpret the variability of gamma-ray luminosity. In addition, we discuss the possibility of restarting the central engine to produce the X-ray flares with required energy.