The Mysterious Magnetospheres of Magnetars

TL;DR

This paper explores the observational and theoretical aspects of magnetar magnetospheres, focusing on their steady hard X-ray emissions, dissipative processes, and quantum electrodynamics effects like photon splitting and pair creation.

Contribution

It provides a comprehensive analysis of magnetar magnetospheres, emphasizing dissipative processes, Comptonization, polarization, and potential QED signatures in their X-ray emissions.

Findings

Identification of key dissipative processes in magnetar magnetospheres

Discussion of potential observational signatures of photon splitting and pair creation

Analysis of the role of Comptonization and polarization in X-ray emission

Abstract

Magnetars are the most luminous compact objects in the stellar mass range observed in the Milky Way, with giant flares of hard X-ray power ~10^45 erg/sec being detected from three soft gamma repeaters in the Galactic neighborhood. Periodicity seen in magnetar persistent emission, and a distinctive "spin-down" lengthening of this period, have driven the paradigm that strongly-magnetized neutron stars constitute these fascinating sources. The steady X-ray emission includes both thermal atmospheric components, and magnetospheric contributions that are manifested as hard X-ray "tails." This paper addresses observational and theoretical elements pertinent to the steady hard X-ray emission of magnetars, focusing on dissipative processes in their magnetospheres, and elements of Comptonization and polarization. It also discusses the action and possible signatures of the exotic and fundamental QED mechanisms of photon splitting and magnetic pair creation, and the quest for their observational vindication.