The impulsive phase of magnetar giant flares: assessing linear tearing as the trigger mechanism

Elenbaas, C.; Watts, Anna L.; Turolla, R.

doi:10.1093/mnras/stv2860

Cited by 21 publications

(15 citation statements)

References 115 publications

(142 reference statements)

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“…Thus, if soft gamma-ray emission is produced concurrently with magnetic reconnections (Thompson & Duncan 1995Gill & Heyl 2010;Elenbaas et al 2016), the absence of correlations between FRBs and hyper-flares can constrain the magnetar scenario (if the soft gamma-ray emission is ubiquitous). Based on these results, we encourage further soft gamma-ray searches especially with Swift.…”

Section: Possible Constraints On the Magnetar Scenariomentioning

confidence: 99%

A burst in a wind bubble and the impact on baryonic ejecta: high-energy gamma-ray flashes and afterglows from fast radio bursts and pulsar-driven supernova remnants

Murase

Kashiyama

Mészáros

2016

Mon. Not. R. Astron. Soc.

266

282

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Tenuous wind bubbles, which are formed by the spin-down activity of central compact remnants, are relevant in some models of fast radio bursts (FRBs) and superluminous supernovae. We study their high-energy signatures, focusing on the role of pair-enriched bubbles produced by young magnetars, rapidly-rotating neutron stars, and magnetized white dwarfs. (i) First, we study the nebular properties and the conditions allowing for escape of high-energy gamma-rays and radio waves, showing that their escape is possible for nebulae with ages of 10 − 100 yr. In the rapidly-rotating neutron star scenario, we find that radio emission from the quasi-steady nebula itself may be bright enough to be detected especially at sub-mm frequencies, which is relevant as a possible counterpart of pulsar-driven SNe and FRBs. (ii) Second, we consider the fate of bursting emission in the nebulae. We suggest that an impulsive burst may lead to a highly relativistic flow, which would interact with the nebula. If the shocked nebula is still relativistic, pre-existing non-thermal particles in the nebula can be significantly boosted by the forward shock, leading to short-duration (maybe millisecond or longer) high-energy gamma-ray flashes. Possible dissipation at the reverse shock may also lead to gamma-ray emission. (iii) After such flares, interactions with the baryonic ejecta may lead to afterglow emission with a duration of days to weeks. In the magnetar scenario, this burst-in-bubble model leads to the expectation that nearby ( 10 − 100 Mpc) high-energy gamma-ray flashes may be detected by the High-Altitude Water Cherenkov Observatory and the Cherenkov Telescope Array, and the subsequent afterglow emission may be seen by radio telescopes such as the Very Large Array. (iv) Finally, we discuss several implications specific to FRBs, including constraints on the emission regions and limits on soft gamma-ray counterparts.

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Section: Possible Constraints On the Magnetar Scenariomentioning

confidence: 99%

A burst in a wind bubble and the impact on baryonic ejecta: high-energy gamma-ray flashes and afterglows from fast radio bursts and pulsar-driven supernova remnants

Murase

Kashiyama

Mészáros

2016

Mon. Not. R. Astron. Soc.

266

282

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“…Moreover, several theoretical works [28,29,30] strongly suggest that the characteristic spatial and temporal scales introduced by reconnecting current sheets embedded in turbulent environments are crucial in shaping the spectral and statistical properties of turbulence. Other astrophysical application in relativistic environments include giant flares observed in the magnetosfere of magnetars [31], and gamma-ray flares observed, e.g., in the Crab nebula [32].…”

Section: Discussionmentioning

confidence: 99%

Fast magnetic reconnection: The ideal tearing instability in classic, Hall, and relativistic plasmas.

Papini

Landi

Zanna

2018

J. Phys.: Conf. Ser.

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Magnetic reconnection is believed to be the driver of many explosive phenomena in Astrophysics, from solar to gamma-ray flares in magnetars and in the Crab nebula. However, reconnection rates from classic MHD models are far too slow to explain such observations. Recently, it was realized that when a current sheet gets sufficiently thin, the reconnection rate of the tearing instability becomes "ideal", in the sense that the current sheet destabilizes on the "macroscopic" Alfvénic timescales, regardless of the Lundquist number of the plasma. Here we present 2D compressible MHD simulations in the classical, Hall, and relativistic regimes. In particular, the onset of secondary tearing instabilities is investigated within Hall-MHD for the first time. In the frame of relativistic MHD, we summarize the main results from Del Zanna et al. [1]: the relativistic tearing instability is found to be extremely fast, with reconnection rates of the order of the inverse of the light crossing time, as required to explain the high-energy explosive phenomena.

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“…However, astrophysical plasmas are often magnetically dominated, in the sense that fields are so strong that the Alfvén speed may approach the speed of light. It is well known that Soft Gamma Repeaters and Anomalous X-ray Pulsars are most likely activated by huge flares of magnetars, neutron stars with fields in their magnetospheres up to a thousand times stronger than in standard radio pulsars, say B ∼ 10 15 G (Usov 1994;Thompson & Duncan 1995;Lyutikov 2006;Elenbaas et al 2016). Fast-spinning newly born magnetars are becoming a favourite model for the inner engine of both long and short Gamma-Ray Bursts Bucciantini et al 2009;Metzger et al 2011;Bucciantini et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Fast reconnection in relativistic plasmas: the magnetohydrodynamics tearing instability revisited

Zanna

Papini

Landi

et al. 2016

Mon. Not. R. Astron. Soc.

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Fast reconnection operating in magnetically dominated plasmas is often invoked in models for magnetar giant flares, for magnetic dissipation in pulsar winds, or to explain the gamma-ray flares observed in the Crab nebula, hence its investigation is of paramount importance in high-energy astrophysics. Here we study, by means of two dimensional numerical simulations, the linear phase and the subsequent nonlinear evolution of the tearing instability within the framework of relativistic resistive magnetohydrodynamics, as appropriate in situations where the Alfvén velocity approaches the speed of light. It is found that the linear phase of the instability closely matches the analysis in classical MHD, where the growth rate scales with the Lundquist number S as S −1/2 , with the only exception of an enhanced inertial term due to the thermal and magnetic energy contributions. In addition, when thin current sheets of inverse aspect ratio scaling as S −1/3 are considered, the so-called ideal tearing regime is retrieved, with modes growing independently on S and extremely fast, on only a few light crossing times of the sheet length. The overall growth of fluctuations is seen to solely depend on the value of the background Alfvén velocity. In the fully nonlinear stage we observe an inverse cascade towards the fundamental mode, with Petschektype supersonic jets propagating at the external Alfvén speed from the X-point, and a fast reconnection rate at the predicted value R ∼ (ln S) −1 .

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The impulsive phase of magnetar giant flares: assessing linear tearing as the trigger mechanism

Cited by 21 publications

References 115 publications

A burst in a wind bubble and the impact on baryonic ejecta: high-energy gamma-ray flashes and afterglows from fast radio bursts and pulsar-driven supernova remnants

A burst in a wind bubble and the impact on baryonic ejecta: high-energy gamma-ray flashes and afterglows from fast radio bursts and pulsar-driven supernova remnants

Fast magnetic reconnection: The ideal tearing instability in classic, Hall, and relativistic plasmas.

Fast reconnection in relativistic plasmas: the magnetohydrodynamics tearing instability revisited

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