A magnetically driven origin for the low luminosity GRB 170817A associated with GW170817

TL;DR

This paper proposes that the low luminosity gamma-ray burst GRB 170817A was caused by a giant flare from a magnetar formed during neutron star merger, offering an alternative to jet-based explanations.

Contribution

It introduces a magnetar giant flare model for GRB 170817A, linking the burst's properties to magnetic energy release during hypermassive neutron star collapse.

Findings

Magnetar giant flares have luminosity and energetics similar to GRB 170817A.

The model predicts similar bursts in future neutron star mergers.

Magnetar magnetic field energy release can explain low-luminosity short GRBs.

Abstract

The gamma-ray burst GRB 170817A associated with GW170817 is subluminous and subenergetic compared with other typical short GRBs. It may be due to a relativistic jet viewed off-axis, or a structured jet, or cocoon emission. Giant flares from magnetars may possibly be ruled out. However, the luminosity and energetics of GRB 170817A is coincident with that of magnetar giant flares. After the coalescence of the binary neutron star, a hypermassive neutron star may be formed. The hypermassive neutron star may have magnetar-strength magnetic field. During the collapse of the hypermassive neutron star, the magnetic field energy will also be released. This giant-flare-like event may explain the the luminosity and energetics of GRB 170817A. Bursts with similar luminosity and energetics are expected in future neutron star-neutron star or neutron star-black hole mergers.