Magnetars: the physics behind observations. A review

Abstract

Magnetars are the strongest magnets in the present universe and the combination of extreme magnetic field, gravity and density makes them unique laboratories to probe current physical theories (from quantum electrodynamics to general relativity) in the strong field limit. Magnetars are observed as peculiar, burst-active x-ray pulsars, the anomalous x-ray pulsars (AXPs) and the soft gamma repeaters (SGRs); the latter emitted also three 'giant flares', extremely powerful events during which luminosities can reach up to 10(47) erg s(-1) for about one second. The last five years have witnessed an explosion in magnetar research which has led, among other things, to the discovery of transient, or 'outbursting', and 'low-field' magnetars. Substantial progress has been made also on the theoretical side. Quite detailed models for explaining the magnetars' persistent x-ray emission, the properties of the bursts, the flux evolution in transient sources have been developed and confronted with observations. New insight on neutron star asteroseismology has been gained through improved models of magnetar oscillations. The long-debated issue of magnetic field decay in neutron stars has been addressed, and its importance recognized in relation to the evolution of magnetars and to the links among magnetars and other families of isolated neutron stars. The aim of this paper is to present a comprehensive overview in which the observational results are discussed in the light of the most up-to-date theoretical models and their implications. This addresses not only the particular case of magnetar sources, but the more fundamental issue of how physics in strong magnetic fields can be constrained by the observations of these unique sources.

The rotation-powered nature of some soft gamma-ray repeaters and anomalous X-ray pulsars

“…In this line we would like to point out that, at present, Jaziel G. Coelho et al: On the nature of some SGRs and AXPs as rotation-powered neutron stars eleven SGRs/AXPs have been identified as transient sources, i.e. sources which show flux variations by a factor ∼(10-1000) over the quiescent level (see, e.g., Turolla et al 2015), in timescales from days to months. Such a variations are usually accompanied by an enhancement of the bursting activity.…”

Electromagnetic fields and anomalous transports in heavy-ion collisions—a pedagogical review

“…It is much larger than the masses squared of electron, m 2 e , and light quarks, m 2 u , m 2 d , and thus is capable of inducing significant quantum effects. It is also larger than the magnetic fields of neutron stars including the magnetars which may have surface magnetic fields of the order of 10 14 − 10 15 Gauss [74,75]. Therefore the magnetic fields generated in high-energy heavy-ion collisions are among the strongest ones that we have ever known in current universe.…”

Relaxation of the chiral imbalance in dense matter of a neutron star

“…The matrix element for the ep collision, due to the electromagnetic interaction, has the form, M = ie 2 (k 1 − k 2 ) 2ē (p 2 )γ μ e(p 1 ) ·p(k 2 )γ μ p(k 1 …”

“…Some neutron stars (NS) can possess extremely strong magnetic fields B 10 15 G. These NSs are called magnetars [1]. Despite long observational history of magnetars and numerous theoretical models for the generation of their magnetic fields, nowadays there is no commonly accepted mechanism explaining the origin of magnetic fields in these compact stars.…”