Gravitational wave signature of proto-neutron star convection: I. MHD numerical simulations

Raynaud, Raphaël; Cerdá-Durán, Pablo; Guilet, Jérôme

doi:10.48550/arxiv.2103.12445

Cited by 5 publications

(9 citation statements)

References 61 publications

(94 reference statements)

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“…Future 3D simulations should address the unusual time-frequency structure of the GW signal and the underlying emission mechanisms in magnetorotational hypernova explosions in more detail. Our findings suggest, similar to Raynaud et al (2021) that substantial GW emission may occur later in the explosion phase in hypernovae, which calls for significantly longer simulations as well. As in the case of rapidly rotating, non-magnetised models (Kuroda et al 2014;Andresen et al 2019;Shibagaki et al 2020) genuinely new features may appear in 3D in the GW signals of hypernovae.…”

Section: Discussionsupporting

confidence: 87%

“…As in the case of rapidly rotating, non-magnetised models (Kuroda et al 2014;Andresen et al 2019;Shibagaki et al 2020) genuinely new features may appear in 3D in the GW signals of hypernovae. In addition to the GW fingerprint of magnetoconvection and and α-Ω dynamo in the PNS (Raynaud et al 2021), the magnetic fields generated by the magnetorotational instability (Balbus & Hawley 1991;Akiyama et al 2003) or dynamo amplification within the gain region or at the PNS surface may leave unexpected traces in the GW signals. Although the odds are stacked against a nearby hypernova explosion, the GW emission may have significant potential to elucidate the nature of an extreme supernova explosion in case of such a lucky event.…”

Section: Discussionmentioning

confidence: 99%

“…Alternatively, there might be some instability at the base of the magnetically collimated jets, or oscillatory modes might be excited by the interplay of magnetic fields, convection, and differential rotation inside the PNS. It is interesting, though that Raynaud et al (2021) recently found strong GW emission in anelastic 3D MHD simulations of rapidly rotating PNSs without accretion, with several prominent frequency peaks that they attributed to the excitation of inertial modes. Due to the restriction of axisymmetry, one should not expect model m15afB12 to resemble any of the 3D simulations of Raynaud et al (2021) in terms of mode structure and mode excitation.…”

Section: Advanced Explosion Phasementioning

confidence: 99%

“…It is interesting, though that Raynaud et al (2021) recently found strong GW emission in anelastic 3D MHD simulations of rapidly rotating PNSs without accretion, with several prominent frequency peaks that they attributed to the excitation of inertial modes. Due to the restriction of axisymmetry, one should not expect model m15afB12 to resemble any of the 3D simulations of Raynaud et al (2021) in terms of mode structure and mode excitation. However, model m39afB12 provides another hint that new, relatively powerful GW emission processes may operate in rapidly rotating, strongly magnetised PNSs.…”

Section: Advanced Explosion Phasementioning

confidence: 99%

“…Studies of GW emission from rotating magnetised stellar cores have so far been confined to the collapse, bounce, and early post-bounce phase (Obergaulinger et al 2006;Scheidegger et al 2010;Takiwaki & Kotake 2011). Waveform predictions from anelastic long-time magnetohydrodynamic (MHD) simulations of PNS convection in rapidly rotating neutron stars have recently also become available (Raynaud et al 2021). The impact of magnetic fields in non-rotating models (Obergaulinger et al 2014) and the combined impact of rotation and magnetic fields (Obergaulinger & Aloy 2020) on supernova dynamics have been explored more systematically across a wider range of the parameter space already by means of long-time simulations including MHD and neutrino transport, but for the GW signal, such an exploration of parameter space is still lacking.…”

Section: Introductionmentioning

confidence: 99%

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Gravitational Wave Signals from Two-Dimensional Core-Collapse Supernova Models with Rotation and Magnetic Fields

Jardine,

Powell,

Müller

2021

Preprint

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We investigate the impact of rotation and magnetic fields on the dynamics and gravitational wave emission in 2D core-collapse supernova simulations with neutrino transport. We simulate 16 different models of 15 M and 39 M progenitor stars with various initial rotation profiles and initial magnetic fields strengths up to 10 12 G, assuming a dipolar field geometry in the progenitor. Strong magnetic fields generally prove conducive to shock revival, though this trend is not without exceptions. The impact of rotation on the post-bounce dynamics is more variegated, in line with previous studies. A significant impact on the time-frequency structure of the gravitational wave signal is found only for rapid rotation or strong initial fields. For rapid rotation, the angular momentum gradient at the proto-neutron star surface can appreciably affect the frequency of the dominant mode, so that known analytic relations for the high-frequency emission band no longer hold. In the case of two magnetorotational explosion models, the time-frequency structure of the post-bounce emission appears rather different from neutrino-driven explosions. In one of these two models, a new high-frequency emission component of significant amplitude emerges about 200 ms after the burst of gravitational wave emission around shock revival has subsided. This emission is characterised by broad-band power well into the kHz range. Its emission mechanism remains unclear and needs to be investigated further. We also estimate the maximum detection distances for our waveforms. The magnetorotational models do not stick out for higher detectability during the post-bounce and explosion phase.

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Section: Discussionsupporting

confidence: 87%

Section: Discussionmentioning

confidence: 99%

Section: Advanced Explosion Phasementioning

confidence: 99%

Section: Advanced Explosion Phasementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Gravitational Wave Signals from Two-Dimensional Core-Collapse Supernova Models with Rotation and Magnetic Fields

Jardine,

Powell,

Müller

2021

Preprint

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MRI-drivenαΩ dynamos in protoneutron stars

Reboul-Salze

Guilet

Raynaud

et al. 2022

A&A

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Context. Magnetars are highly magnetized neutron stars that can produce a wide diversity of X-ray and soft gamma-ray emissions that are powered by magnetic dissipation. Their magnetic dipole is constrained in the range of 10 14 to 10 15 G by the measurement of their spin-down. In addition to fast rotation, these strong fields are also invoked to explain extreme stellar explosions, such as hypernovae, which are associated with long gamma-ray bursts and superluminous supernovae. A promising mechanism for explaining magnetar formation is the amplification of the magnetic field by the magnetorotational instability (MRI) in fast-rotating protoneutron stars (PNS). This scenario is supported by recent global incompressible models, which showed that a dipole field with magnetar-like intensity can be generated from small-scale turbulence. However, the impact of important physical ingredients, such as buoyancy and density stratification, on the efficiency of the MRI in generating a dipole field is still unknown. Aims. We assess the impact of the density and entropy profiles on the MRI dynamo in a global model of a fast-rotating PNS. The model focuses on the outer stratified region of the PNS that is stable to convection. Methods. Using the pseudo-spectral code MagIC, we performed 3D Boussinesq and anelastic magnetohydrodynamics simulations in spherical geometry with explicit diffusivities and with differential rotation forced at the outer boundary. The thermodynamic background of the anelastic models was retrieved from the data of 1D core-collapse supernova simulations from the Garching group. We performed a parameter study in which we investigated the influence of different approximations and the effect of the thermal diffusion through the Prandtl number. Results. We obtain a self-sustained turbulent MRI-driven dynamo. This confirms most of our previous incompressible results when they are rescaled for density. The MRI generates a strong turbulent magnetic field and a nondominant equatorial dipole, which represents about 4.3% of the averaged magnetic field strength. Interestingly, an axisymmetric magnetic field at large scales is observed to oscillate with time, which can be described as a mean-field αΩ dynamo. By comparing these results with models without buoyancy or density stratification, we find that the key ingredient explaining the appearance of this mean-field behavior is the density gradient. Buoyancy due to the entropy gradient damps turbulence in the equatorial plane, but it has a relatively weak influence in the low Prandtl number regime overall, as expected from neutrino diffusion. However, the buoyancy starts to strongly impact the MRI dynamo for Prandtl numbers close to unity. Conclusions. Our results support the hypothesis that the MRI is able to generate magnetar-like large-scale magnetic fields. The results furthermore predict the presence of a αΩ dynamo in the protoneutron star, which could be important to model in-situ magnetic field amplification in global models of core-collapse supernovae or binary ...

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Three-dimensional core-collapse supernovae with complex magnetic structures: I. Explosion dynamics

Bugli,

Guilet,

Obergaulinger

2021

Preprint

Self Cite

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Magnetic fields can play a major role in the dynamics of outstanding explosions associated to violent events such as GRBs and hypernovae, since they provide a natural mechanism to harness the rotational energy of the central proto-neutron star and power relativistic jets through the stellar progenitor. As the structure of such fields is quite uncertain, most numerical models of MHD-driven core-collapse supernovae consider an aligned dipole as initial magnetic field, while the field's morphology can actually be much more complex. We present threedimensional simulations of core-collapse supernovae with more realistic magnetic structures, such as quadrupolar fields and, for the first time, a tilted dipolar field. Configurations other than an aligned dipole produce weaker explosions and less collimated outflows, but can at the same time be more efficient in extracting the rotational energy from the PNS. This energy is then stored in the surroundings of the PNS, rather than powering the polar jets. A significant axial dipolar component is also produced by models starting with a quadrupolar field, pointing to an effective dynamo mechanism operating in proximity of the PNS surface.

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Gravitational wave signature of proto-neutron star convection: I. MHD numerical simulations

Cited by 5 publications

References 61 publications

Gravitational Wave Signals from Two-Dimensional Core-Collapse Supernova Models with Rotation and Magnetic Fields

Gravitational Wave Signals from Two-Dimensional Core-Collapse Supernova Models with Rotation and Magnetic Fields

MRI-drivenαΩ dynamos in protoneutron stars

Three-dimensional core-collapse supernovae with complex magnetic structures: I. Explosion dynamics

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