Magnetically-driven explosions of rapidly-rotating white dwarfs following Accretion-Induced Collapse

Abstract

We present 2D multi-group flux-limited diffusion magnetohydrodynamics (MHD) simulations of the Accretion-Induced Collapse (AIC) of a rapidly-rotating white dwarf. We focus on the dynamical role of MHD processes after the formation of a millisecond-period protoneutron star. We find that including magnetic fields and stresses can lead to a powerful explosion with an energy of a few Bethe, rather than a weak one of at most 0.1 Bethe, with an associated ejecta mass of ~0.1Msun, instead of a few 0.001Msun. The core is spun down by ~30% within 500ms after bounce, and the rotational energy extracted from the core is channeled into magnetic energy that generates a strong magnetically-driven wind, rather than a weak neutrino-driven wind. Baryon loading of the ejecta, while this wind prevails, precludes it from becoming relativistic. This suggests that a GRB is not expected to emerge from such AICs during the early protoneutron star phase, except in the unlikely event that the massive white dwarf has sufficient mass to lead to black hole formation. In addition, we predict both negligible 56Ni-production (that should result in an optically-dark, adiabatically-cooled explosion) and the ejection of 0.1Msun of material with an electron fraction of 0.1-0.2. Such pollution by neutron-rich nuclei puts strong constraints on the possible rate of such AICs. Moreover, being free from ``fallback,'' such highly-magnetized millisecond-period protoneutron stars may later become magnetars, and the magnetically-driven winds may later transition to Poynting-flux-dominated, relativistic winds, eventually detectable as GRBs at cosmological distances. However, the low expected event rate of AICs will constrain them to be, at best, a small subset of GRB and/or magnetar progenitors.

16 pages, 8 figures, paper accepted to ApJ; High resolution version available at http://hermes.as.arizona.edu/~luc/aic_mhd/aic_mhd.html

References in corpus (10)

• Gamma-Ray Bursts: Progress, Problems & Prospects
• Fallback accretion in the aftermath of a compact binary merger
• 3D Collapse of Rotating Stellar Iron Cores in General Relativity including Deleptonization and a Nuclear Equation of State
• Features of the Acoustic Mechanism of Core-Collapse Supernova Explosions
• Magnetorotational collapse of massive stellar cores to neutron stars: Simulations in full general relativity
• Burial of the polar magnetic field of an accreting neutron star. II. Hydromagnetic stability of axisymmetric equilibria
• A Local Model for Angular Momentum Transport in Accretion Disks Driven by the Magnetorotational Instability
• General Relativistic Simulations of Slowly and Differentially Rotating Magnetized Neutron Stars
• Double Neutron Stars: Evidence For Two Different Neutron-Star Formation Mechanisms
• A Two-Dimensional MagnetoHydrodynamics Scheme for General Unstructured Grids

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