The Optically Thick Rotating Magnetic Wind from a Massive White Dwarf Merger Product. II. Axisymmetric Magnetohydrodynamic Simulations

Abstract

We numerically construct a series of axisymmetric rotating magnetic wind solutions, aiming at exploring the observation properties of massive white dwarf (WD) merger remnants with a strong magnetic field, a fast spin, and an intense mass loss, as inferred for WD J005311. We investigate the magnetospheric structure and the resultant spin-down torque exerted to the merger remnant with respect to the surface magnetic flux Φ _* , spin angular frequency Ω _* and the mass-loss rate $\dot{M}$ . We confirm that the wind properties for $\sigma \equiv {{\rm{\Phi }}}_{* }^{2}{{\rm{\Omega }}}_{* }^{2}/\dot{M}{v}_{\mathrm{esc}}^{3}\gtrsim 1$ significantly deviate from those of the spherical Parker wind, where v _esc is the escape velocity at stellar surface. For such a rotating magnetic wind sequence, we find (i) a quasiperiodic mass eruption triggered by magnetic reconnection along with the equatorial plane and (ii) a scaling relation for the spin-down torque $T\approx (1/2)\times \dot{M}{{\rm{\Omega }}}_{* }{R}_{* }^{2}{\sigma }^{1/4}$ . We apply our results to discuss the spin-down evolution and wind anisotropy of massive WD merger remnants, the latter of which could be probed by a successive observation of WD J005311 using Chandra.

Keywords

• Stellar winds
• White dwarf stars
• Stellar rotation
• Magnetohydrodynamics