Accessibility of the stochastic gravitational wave background from magnetars to the interferometric gravitational wave detectors

Magnetars have been proposed as sources of gravitational waves, potentially observable by current and future terrestrial gravitational-wave detectors. In this paper, we calculate the stochastic gravitational wave background generated by summing the contributions from all magnetars in the Universe, and we study its accessibility to the second- and third-generation gravitational-wave detector networks. We perform systematic scans of the parameter space in this model, allowing the magnetic field, the ellipticity, the initial period, and the rate of magnetars to vary over the currently believed range of values. We also consider different proposed configurations of the magnetic field (poloidal, toroidal, and twisted torus) and different proposed star-formation histories. We identify regions in the parameter space of poloidal and toroidal models that will be accessible to the second- and third-generation gravitational-wave detectors and conclude that the twisted-torus models are likely out of reach of these detectors. The poloidal field configuration with a type II superconductor equation of state in the interior, or with a highly disordered magnetic field, and the toroidal configuration with a very strong toroidal magnetic field in the interior (>1016 G) are the most promising in terms of gravitational-wave detection.