Document Type

Article

Publication Date

7-1-2025

Abstract

The merger origin long GRB 211211A was a class (re-)defining event. A precursor was identified with a s separation from the main burst, as well as a claimed candidate quasi-periodic oscillation (QPO) with a frequency Hz. Here, we explore the implications of the precursor, assuming the quasi-periodicity is real. The precursor variability time-scale requires relativistic motion with a Lorentz factor, and implies an engine-driven jetted outflow. The declining amplitude of the consecutive pulses requires an episodic engine with an 'on/off' cycle consistent with the QPO. For a black-hole central engine, the QPO can have its origin in Lense-Thirring precession of the inner disc at (gravitational radii) for a mass M, and for 4.5$]]> M and dimensionless spin. Alternatively, at a disc density of g cm, the required magnetic field strength for a QPO via magnetohydrodynamic effects will be of the order of G. If the central engine is a short-lived magnetar or hypermassive neutron star, then a low-frequency QPO can be produced via instabilities within the disc at a radius of km, for a disc density g cm and magnetic field G. The QPO cannot be coupled to the neutron star spin, as the co-rotation radius is beyond the scale of the disc. Neither engine can be ruled out-however, we favour an origin for the precursor candidate QPO as early jet-disc coupling for a neutron star-black hole merger remnant with mass 4.5$]]> M.

Publication Source (Journal or Book title)

Monthly Notices of the Royal Astronomical Society

First Page

2727

Last Page

2744

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