Prompt Periodicity in the GRB 211211A Precursor: Black-hole or magnetar engine?

Lamb, GP ORCID: 0000-0001-5169-4143, Baxter, T, Omand, CMB ORCID: 0000-0002-9646-8710, Dimple, McGrath, Z, Turnbull, C, Burns, E, Hamidani, H, Mandel, I ORCID: 0000-0002-6134-8946, Page, KL ORCID: 0000-0001-5624-2613, Rosswog, S ORCID: 0000-0002-3833-8520, Sarin, N, Blain, A, Datrier, L ORCID: 0000-0002-0290-3129, Kobayashi, S ORCID: 0000-0001-7946-4200, Levan, A, Starling, R, Gompertz, B ORCID: 0000-0002-5826-0548, Habeeb, N, Nguyen, K et al (2025) Prompt Periodicity in the GRB 211211A Precursor: Black-hole or magnetar engine? Monthly Notices of the Royal Astronomical Society, 450 (3). ISSN 0035-8711

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Abstract

The merger origin long GRB 211211A was a class (re-)defining event. A precursor was identified with a ∼1 s separation from the main burst, as well as a claimed candidate quasi-periodic oscillation (QPO) with a frequency ∼20 Hz. Here, we explore the implications of the precursor, assuming the quasi-periodicity is real. The precursor variability timescale requires relativistic motion with a Lorentz factor Γ ≳ 80, 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 disk at ∼6 − 9 rg (gravitational radii) for a mass M• ≤ 4.5 M⊙, and ≲ 7 rg for M• > 4.5 M⊙ and dimensionless spin χ ∼ 0.3 − 0.9. Alternatively, at a disk density of ∼108 − 12 g cm−3, the required magnetic field strength for a QPO via magnetohydrodynamic effects will be on the order B ∼ 1012 − 14 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 disk at a radius of ∼20 − 70 km, for a disk density ∼109 − 12 g cm−3 and magnetic field ≳ 1013 − 14 G. The QPO cannot be coupled to the neutron star spin, as the co-rotation radius is beyond the scale of the disk. Neither engine can be ruled out – however, we favour an origin for the precursor candidate QPO as early jet-disk coupling for a neutron star – black hole merger remnant with mass M• > 4.5 M⊙.

Item Type:	Article
Uncontrolled Keywords:	5101 Astronomical Sciences; 51 Physical Sciences; 0201 Astronomical and Space Sciences; Astronomy & Astrophysics; 5101 Astronomical sciences; 5107 Particle and high energy physics; 5109 Space sciences
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Divisions:	Astrophysics Research Institute
Publisher:	Oxford University Press (OUP)
Date of acceptance:	29 May 2025
Date of first compliant Open Access:	13 June 2025
Date Deposited:	13 Jun 2025 13:08
Last Modified:	03 Jul 2025 13:00
DOI or ID number:	10.1093/mnras/staf892
URI:	https://researchonline.ljmu.ac.uk/id/eprint/26585

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