GRB afterglow plateaus and Gravitational Waves: multi-messenger signature of a millisecond magnetar?

TL;DR

This paper explores the potential link between gamma-ray burst afterglow plateaus and gravitational wave signals from a nascent magnetar, proposing a multi-messenger approach to detect these phenomena.

Contribution

It introduces a novel scenario connecting X-ray afterglow features with gravitational wave emissions from a millisecond magnetar undergoing a secular bar-mode instability.

Findings

Detectable gravitational wave signals could be associated with gamma-ray burst afterglow plateaus.

The gravitational wave peak may be delayed relative to the gamma-ray burst trigger.

Long-duration gravitational wave signals could be observed by advanced interferometers.

Abstract

The existence of a shallow decay phase in the early X-ray afterglows of gamma-ray bursts is a common feature. Here we investigate the possibility that this is connected to the formation of a highly magnetized millisecond pulsar, pumping energy into the fireball on timescales longer than the prompt emission. In this scenario the nascent neutron star could undergo a secular bar-mode instability, leading to gravitational wave losses which would affect the neutron star spin-down. In this case, nearby gamma-ray bursts with isotropic energies of the order of 1e50 ergs would produce a detectable gravitational wave signal emitted in association with an observed X-ray light-curve plateau, over relatively long timescales of minutes to about an hour. The peak amplitude of the gravitational wave signal would be delayed with respect to the gamma-ray burst trigger, offering gravitational wave interferometers such as the advanced LIGO and Virgo the challenging possibility of catching its signature on the fly.