The early evolution of magnetar rotation – I. Slowly rotating ‘normal’ magnetars

ABSTRACT In the seconds following their formation in core-collapse supernovae, ‘proto’-magnetars drive neutrino-heated magnetocentrifugal winds. Using a suite of two-dimensional axisymmetric magnetohydrodynamic simulations, we show that relatively slowly rotating magnetars with initial spin periods P?0 = 50–500 ms down rapidly during neutrino Kelvin–Helmholtz cooling epoch. These are representative those inferred for normal Galactic pulsars, and much slower than invoked gamma-ray bursts superluminous supernovae. Since flow is non-relativistic at early times, because Alfvén radius larger proto-magnetar radius, spin-down millions times more efficient typically used dipole formula. Quasi-periodic plasmoid ejections from closed zone enhance spin-down. For polar magnetic field strengths B0 ? 5 × 1014 G, time-scale can be shorter time-scale. 1015 it order phases. We compute evolution proto-magnetars as function B0, P?0, mass (M). Proto-magnetars born greater $\simeq 1.3\times 10^{15}\, {\rm \, G}\, (P_{\star 0}/{400\, \rm ms})^{-1.4}(M/1.4\, M}_\odot)^{2.2}$ to >1 s just first few evolution, well before end epoch onset classic Spin-down lower M P?0. discuss implications observed magnetars, including discrepancy between characteristic ages supernova remnant ages. Finally, speculate on origin 1E 161348?5055 RCW 103, potential other ultra-slowly magnetars.