GRB 211211A: a Prolonged Central Engine under a Strong Magnetic Field Environment

Abstract

Recently, a kilonova-associated gamma-ray burst (GRB 211211A), whose light curve consists of a precursor (∼0.2 s), a hard spiky emission (∼10 s), and a soft long extended emission (∼40 s), has attracted great attention. Kilonova association could prove its merger origin, while the detection of the precursor can be used to infer at least one highly magnetized neutron star (NS) being involved in the merger. In this case, a strong magnetic flux Φ is expected to surround the central engine of GRB 211211A. Here we suggest that when Φ is large enough, the accretion flow could be halted far from the innermost stable radius, which will significantly prolong the lifetime of the accretion process, and so the GRB duration. For example, we show that as long as the central black hole (BH) is surrounded by a strong magnetic flux Φ ∼ 1029cm2 G, an accretion flow with M ̇ ini ≃ 0.1 M ⊙ s − 1 could be halted at 40 times the gravitational radius and be slowly transferred into the black hole on the order of ∼10 s, which naturally explains the duration of hard spiky emission. After most of the disk mass has been accreted onto the BH, the inflow rate will be reduced, so a long and soft extended emission is expected when a new balance between the magnetic field and the accretion current is reconstructed at a larger radius. Our results further support that the special behavior of GRB 211211A is mainly due to the strong magnetic field of its progenitor stars.

Search for Coincident Gravitational Waves and Long Gamma-Ray Bursts from 4-OGC and the Fermi-GBM/Swift-BAT Catalog

“…GW observation can provide irreplaceable information for the source properties of compact objects, including their mass, spin, tidal deformability, luminosity distance, and inclination angle, which is crucial to distinguish different scenarios between binary neutron stars and neutron star-black hole mergers (e.g., Gao et al 2022;Gompertz et al 2022;Yang et al 2022). Even with nondetection, GW can constrain the exclusion distance and provide evidence for alternative explanations for the engine of GRB 211211A, such as neutron star-white dwarf mergers (Yang et al 2022).…”

“…Additional interesting features were reported, including a quasiperiodic oscillated precursor that occurred ∼1 s prior to the main emission (Xiao et al 2022), and a high-energy (>100 MeV) gamma-ray afterglow lasting ∼ 2 × 10 4 s that occurred ∼1000 s after the burst (Mei et al 2022;Zhang et al 2022). Several models have been proposed to explain the emission mechanism of GRB 211211A; for instance, fast-cooling synchrotron radiation after a binary neutron star merger (Gompertz et al 2022), magnetic barrier effect involving a magnetar progenitor (Gao et al 2022), a neutron star-white dwarf merger (Yang et al 2022), or thermal emission from heated dust as an alternative scenario to kilonova (Waxman et al 2022). The associated kilonova clearly indicates the progenitor of GRB 211211A is a binary merger with at least one neutron star, suggesting the prospect of detecting a GW signal from events of this kind (however, see Waxman et al 2022 for an alternative explanation).…”

“…The associated kilonova clearly indicates the progenitor of GRB 211211A is a binary merger with at least one neutron star, suggesting the prospect of detecting a GW signal from events of this kind (however, see Waxman et al 2022 for an alternative explanation). GW observation provides unique information about the source's mass and spin (Veitch et al 2015), which may help disentangle different models (Gao et al 2022;Gompertz et al 2022;Waxman et al 2022;Yang et al 2022). Unfortunately, none of the GW detectors were in observation mode at the time of the GRB 211211A.…”

Long-duration Gamma-Ray Burst and Associated Kilonova Emission from Fast-spinning Black Hole–Neutron Star Mergers

“…Yang et al (2022) proposed that the merger of a nearequal-mass NS-white-dwarf binary could well explain the ME of GRB 211211A, since the accretion of some high-angular momentum white-dwarf debris onto the remnant NS could prolong the burst duration. Gao et al (2022) suggested that a strong magnetic flux may surround the central engine of GRB 211211A, resulting in a long-duration accretion process, due to the magnetic barrier effect (Proga & Zhang 2006;Liu et al 2012).…”

Repeating Fast Radio Bursts from Neutron Star Binaries: Multi-band and Multi-messenger Opportunities

“…This event suggests that a magnetar is most likely involved in the merger, where the QPOs in the precursor are a result of a catastrophic giant flare accompanied by torsional or crustal oscillations of the magnetar. The long duration of the GRB produced by a merger is supported by the prolonged lifetime of the accretion process by the magnetic barrier effect [53,[56][57][58]. The long GeV emission is a result of a long deceleration time of the GRB jet in a low-density circumburst medium, and the GeV excess can be explained with the inverse-Compton scattering of soft photons from the kilonova by hot electrons in the relativistic jet, both of which are also consistent with the compact binary merger scenario [54,55].…”