A Broadband Emission Model of Magnetar Wind Nebulae

TL;DR

This paper develops a broadband emission model for magnetar wind nebulae, applying it to a specific magnetar, predicting gamma-ray flux, and highlighting the need for further observational and theoretical studies to understand magnetar winds.

Contribution

The paper introduces a modified broadband emission model for magnetar wind nebulae, adapted from pulsar wind nebula models, to analyze magnetar-specific properties with limited observational data.

Findings

Model predicts gamma-ray flux detectable by CTA.

MWN around 1E 1547.0-5408 is faint due to low spin-down power.

Spectral analysis cannot confirm initial millisecond period hypothesis.

Abstract

Angular momentum loss by the plasma wind is considered as a universal feature of isolated neutron stars including magnetars. The wind nebulae powered by magnetars allow us to compare the wind properties and the spin-evolution of magnetars with those of rotation-powered pulsars (RPPs). In this paper, we construct a broadband emission model of magnetar wind nebulae (MWNe). The model is similar to past studies of young pulsar wind nebulae (PWNe) around RPPs, but is modified for the application to MWNe that have far less observational information than the young PWNe. We apply the model to the MWN around the youngest ($\sim$ 1kyr) magnetar 1E 1547.0-5408 that has the largest spin-down power $L_{\rm spin}$ among all the magnetars. However, the MWN is faint because of low $L_{\rm spin}$ of 1E 1547.0-5408 compared with the young RPPs. Since most of parameters are not well constrained only by an X-ray flux upper limit of the MWN, we adopt the model parameters from young PWN Kes 75 around PSR J1846-0258 that is a peculiar RPP showing magnetar-like behaviors. The model predicts $\gamma$-ray flux that will be detected in a future TeV $\gamma$-ray observation by {\it CTA}. The MWN spectrum does not allow us to test hypothesis that 1E 1547.0-5408 had milliseconds period at its birth because the particles injected early phase of evolution are suffered from severe adiabatic and synchrotron losses. Further both observational and theoretical studies of the wind nebulae around magnetars are required to constrain the wind and spin-down properties of magnetars.