Ultrahigh energy cosmic ray acceleration in newly born magnetars and their associated gravitational wave signatures

TL;DR

This paper explores how newly born magnetars can accelerate particles to ultrahigh energies and examines their potential gravitational wave signatures, suggesting detectable signals for future observatories.

Contribution

It introduces a model with varied initial voltages in magnetar winds to better fit the observed cosmic ray spectrum and predicts enhanced gravitational wave background signals.

Findings

Magnetar populations can produce gravitational wave backgrounds detectable by future detectors.

Adjusting initial voltage distributions softens the cosmic ray spectrum to match observations.

Predicted gravitational wave signals could be up to four orders of magnitude higher than standard models.

Abstract

Newly born magnetars are good candidate sources of ultrahigh energy cosmic rays. These objects can in principle easily accelerate particles to the highest energies required to satisfy the ultrahigh energy cosmic ray scenario (E~10^{20-21} eV), thanks to their important rotational and magnetic energy reservoirs. Their acceleration mechanism, based on unipolar induction, predicts however a hard particle injection that does not fit the observed ultrahigh energy cosmic ray spectrum. Here we show that an adequate distribution of initial voltages among magnetar winds can be found to soften the spectrum. We discuss the effect of these distributions for the stochastic gravitational wave background signature produced by magnetars. The magnetar population characteristics needed to fit the ultrahigh energy cosmic ray spectrum could lead in most optimistic cases to gravitational wave background signals enhanced of up to four orders of magnitudes in the range of frequency 1-100 Hz, compared to the standard predictions. These signals could reach the sensitivities of future detectors such as DECIGO or BBO.