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

Understand

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.