Accumulation of Elastic Strain toward Crustal Fracture in Magnetized Neutron Stars

Kojima, Yasufumi

doi:10.3847/1538-4357/ac9184

Cited by 9 publications

(2 citation statements)

References 67 publications

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“…where the radial functions x l and k l (l = 1, 3) are determined using Equations ( 24) and ( 25) (Kojima et al 2022);…”

Section: Quasi-stationary Elastic Responsementioning

confidence: 99%

“…The Lorentz force is comparable in magnitude to the elastic force in the crust. However, only static magneto-elastic equilibria of the crust have been studied thus far (Kojima et al 2021(Kojima et al , 2022Fujisawa et al 2023). These studies demonstrated that neutron star models with strong magnetic fields are possible owing to the elasticity of the crust.…”

Section: Introductionmentioning

confidence: 99%

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Evolutionary deformation toward the elastic limit by a magnetic field confined in the neutron--star crust

Kojima¹,

Kisaka²,

Fujisawa³

2023

Preprint

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Occasional energetic outbursts and anomalous X-ray luminosities are expected to be powered by the strong magnetic field in a neutron star. For a very strong magnetic field, elastic deformation becomes excessively large such that it leads to crustal failure. We studied the evolutionary process driven by the Hall drift for a magnetic field confined inside the crust. Assuming that the elastic force acts against the Lorentz force, we examined the duration of the elastic regime and maximum elastic energy stored before the critical state. The breakup time was longer than that required for extending the field to the exterior, because the tangential components of the Lorentz force vanished in the fragile surface region. The conversion of large magnetic energy, confined to the interior, into Joule heat is considered to explain the power for central compact objects. This process can function without reaching its elastic limit, unless the magnetic energy exceeds 2 × 10 47 erg, which requires an average field strength of 2 × 10 15 G. Thus, the strong magnetic field hidden in the crust is unlikely to cause outbursts. Furthermore, the magnetic field configuration can discriminate between central compact objects and magnetars.

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“…where the radial functions x l and k l (l = 1, 3) are determined using Equations ( 24) and ( 25) (Kojima et al 2022);…”

Section: Quasi-stationary Elastic Responsementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Evolutionary deformation toward the elastic limit by a magnetic field confined in the neutron--star crust

Kojima¹,

Kisaka²,

Fujisawa³

2023

Preprint

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GRB 180128A: A second magnetar giant flare candidate from the Sculptor Galaxy

Trigg,

Burns,

Roberts

et al. 2024

A&A

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Magnetars are slowly rotating neutron stars that possess the strongest magnetic fields known in the cosmos ($10^ G $). They display a range of transient high-energy electromagnetic activity. The brightest and most energetic of these events are the gamma-ray bursts (GRBs) known as magnetar giant flares (MGFs), with isotropic energies $E_ iso erg $. Only seven MGF detections have been made to date: three unambiguous events occurred in our Galaxy and the Magellanic Clouds, and the other four MGF candidates are associated with nearby star-forming galaxies. As all seven identified MGFs are bright at Earth, additional weaker events likely remain unidentified in archival data. We conducted a search of the Fermi Gamma-ray Burst Monitor database for candidate extragalactic MGFs and, when possible, collected localization data from the Interplanetary Network (IPN) satellites. Our search yielded one convincing event, GRB\,180128A. IPN localizes this burst within NGC\,253, commonly known as the Sculptor Galaxy. The event is the second MGF in modern astronomy to be associated with this galaxy and the first time two bursts have been associated with a single galaxy outside our own. Here we detail the archival search criteria that uncovered this event and its spectral and temporal properties, which are consistent with expectations for a MGF. We also discuss the theoretical implications and finer burst structures resolved from various binning methods. Our analysis provides observational evidence of an eighth identified MGF.

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Strong toroidal magnetic fields sustained by the elastic crust in a neutron star

Fujisawa¹,

Kojima²,

Kisaka³

2022

Monthly Notices of the Royal Astronomical Society

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We investigate new solutions for magnetized neutron stars with a barotropic core in magnetohydrodynamic (MHD) equilibrium and a magneto-elastic crust, which was neglected by previous studies concerning stars in MHD equilibrium. The Lorentz force of the barotropic star is purely irrotational and the structures of magnetic fields are constrained. By contrast, a solenoidal component of the Lorentz force exists in the elastic crust and the structures of the magnetic fields are less restricted. We find that the minor solenoidal component in the elastic crust is important for sustaining the strong magnetic field in the core. Unlike previous studies, the toroidal magnetic field exists in the entire region of the core, and we obtain equilibrium states with large toroidal magnetic fields, where the toroidal magnetic energy is larger than the poloidal magnetic energy. The elastic force of the crust sustains an order of 1015 G toroidal magnetic field in the core, and the maximum strength of the toroidal magnetic field is approximately proportional to the crust thickness.

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Accumulation of Elastic Strain toward Crustal Fracture in Magnetized Neutron Stars

Cited by 9 publications

References 67 publications

Evolutionary deformation toward the elastic limit by a magnetic field confined in the neutron--star crust

Evolutionary deformation toward the elastic limit by a magnetic field confined in the neutron--star crust

GRB 180128A: A second magnetar giant flare candidate from the Sculptor Galaxy

Strong toroidal magnetic fields sustained by the elastic crust in a neutron star

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