Modelling spin evolution of magnetars

ABSTRACT The origin and fate of magnetars [young, extremely magnetized neutron stars (NSs)] remains unsolved. Probing their evolution is therefore crucial for investigating possible links to other species isolated NSs, such as the X-ray dim NSs (XDINSs) rotating radio transients (RRATs). Here, we investigate spin magnetars. Two avenues are considered: one with exponentially decaying B-fields, sub- superexponential decay. Using Monte Carlo methods, synthesize magnetar populations using different input distributions physical parameters, initial period, its time derivative, B-field decay time-scale. Additionally, introduce a fade-away procedure that can account fading old magnetars, briefly discuss effect alignment axes. Imposing Galactic core-collapse supernova rate ∼20 kyr−1 strict upper limit on birthrate comparing synthetic observed both manual automatic optimization algorithms our parameter study, find must or superexponentially characteristic time-scale 0.5−10 kyr (with best value ∼4 kyr). In addition, period be less than 2 s. If these constraints kept, conclude there multiple choices physics reproduce population reasonably well. We also may well evolutionary linked XDINSs, whereas they in general unlikely evolve into RRATs.