Ultra-strong Magnetic Fields Research Articles

The Nature of AX J0051-733 in the SMC: A Pulsar Born with Ultrastrong Magnetic Field?

We investigate the nature of the pulsar of the Be/X-ray binary, AX J0051- 733. Although the system has a very short orbital period, it meets the basic definition of Be/X-ray binaries. We argue that, in order to interpret such a short orbital period, the initial magnetic field strength of the pulsar must be between 4.2 x 10(13) - 5 x 10(15) G, if typical values of the parameters chosen. Thus, the pulsar was most likely born as a magnetar. We further suggest that magnetar descendants can also be found among the massive X-ray binaries with extremely short-orbit periods, in addition to among the X-ray binaries with very long pulse periods.

Joint Discussion 2 On the present and future of pulsar astronomy

Neutron stars are formed in supernova explosions. They manifest themselves in many different ways, for example, as pulsars, anomalous X-ray pulsars (AXPs) and soft γ-ray repeaters (SGRs) and the so-called ‘radio-quiet neutron stars’. These objects are made visible by high-energy processes occurring on their surface or in the surrounding region. In most of these objects, ultra-strong magnetic fields are a crucial element in the radio, optical, X-ray and gamma-ray emission processes which dominate the observed spectrum.

Transient pulsed radio emission from a magnetar

Anomalous X-ray pulsars (AXPs) are slowly rotating neutron stars with very bright and highly variable X-ray emission that are believed to be powered by ultra-strong magnetic fields of >10(14) G, according to the 'magnetar' model. The radio pulsations that have been observed from more than 1,700 neutron stars with weaker magnetic fields have never been detected from any of the dozen known magnetars. The X-ray pulsar XTE J1810-197 was revealed (in 2003) as the first AXP with transient emission when its luminosity increased 100-fold from the quiescent level; a coincident radio source of unknown origin was detected one year later. Here we show that XTE J1810-197 emits bright, narrow, highly linearly polarized radio pulses, observed at every rotation, thereby establishing that magnetars can be radio pulsars. There is no evidence of radio emission before the 2003 X-ray outburst (unlike ordinary pulsars, which emit radio pulses all the time), and the flux varies from day to day. The flux at all radio frequencies is approximately equal--and at >20 GHz XTE J1810-197 is currently the brightest neutron star known. These observations link magnetars to ordinary radio pulsars, rule out alternative accretion models for AXPs, and provide a new window into the coronae of magnetars.

Light propagation effects in QED: Effective action approach

The effects of light propagation in constant magnetic and electric backgrounds are considered in the framework of the effective action approach. We use the exact analytic series representation for the one-loop effective action of QED and apply it to the birefringence effect. Analytical results for the light velocity modes are obtained for weak and strong field regime. We present asymptotic formulae for the light velocity modes for the ultra strong magnetic field which can be realized in some neutron stars.

Effect of a strong magnetic field on the surface electric field of strange stars

We made a detailed study of the properties of the electron layer near the quark surface of strange stars with strong (∼10 14 -10 17 G) magnetic fields. The electrostatic potential and the electric field at the quark surface were calculated as functions of the magnetic field intensity of bare strange stars. Using an ultrastrong (B ≥ 2.5×10 16 G) magnetic field, we found that the distribution of electrons becomes an exponential function of radial distance, which is quite different in a magnetic field-free case. We also calculated the variation in gap width between the strange core and the normal nuclear crust for strange stars, which is due to magnetic field effect.

Effect of isovector-scalar meson on neutron-star matter in strong magnetic fields

Within the mean-field approximation to the Lagrangian field theory, we study the effects of isovector-scalar meson δ on nucleon effective masses and the equation of state (EOS) of neutron-star matter in strong magnetic fields. We find that the δ-field leads to a large splitting of proton and neutron effective masses in neutron-star matter. The strength of the δ-field decreases, however, with the increase of the magnetic field and is near zero at ultrastrong field. Although the proton effective mass is found to be highly influenced by magnetic fields, the effect of magnetic fields on the neutron effective mass is negligible. The EOS of neutron-star matter turns out to be stiffer at B < 1015 G but becomes softer at stronger magnetic field after including the δ-field. The effect due to the anomalous magnetic moments of both nucleons and lepton is also studied and is found to be appreciable only at ultrastrong magnetic field (B > 1019 G). In the range of 1015–1018 G, the properties of neutron-star matter remain similar to those without magnetic fields.

High‐Energy Emission from Magnetars

The recently discovered soft gamma-ray emission from the anomalous X-ray pulsar 1E 1841-045 has a luminosity Lγ ~ 1036 ergs s-1. This luminosity exceeds the spin-down power by 3 orders of magnitude and must be fed by an alternative source of energy such as an ultrastrong magnetic field. A gradual release of energy in the stellar magnetosphere is expected if it is twisted and a strong electric current is induced on the closed field lines. We examine two mechanisms of gamma-ray emission associated with the gradual dissipation of this current. (1) A thin surface layer of the star is heated by the downward beam of current-carrying charges, which excite Langmuir turbulence in this layer. As a result, it can reach a temperature kBT ~ 100 keV and emit bremsstrahlung photons up to this characteristic energy. (2) The magnetosphere is also a source of soft gamma rays at a distance of ~100 km from the star, where the electron cyclotron energy is in the kilo-electron volt range. A large electric field develops in this region in response to the outward drag force felt by the current-carrying electrons from the flux of kilo-electron volt photons leaving the star. A seed positron injected in this region undergoes runaway acceleration and upscatters X-ray photons above the threshold for pair creation. The created pairs emit a synchrotron spectrum consistent with the observed 20-100 keV emission. This spectrum is predicted to extend to higher energies and reach a peak at ~1 MeV.

QUARK STARS AND QUANTUM-MAGNETICALLY INDUCED COLLAPSE

Quark matter is expected to exist in the interior of compact stellar objects as neutron stars or even the more exotic strange stars, based on the Bodmer–Witten conjecture. Bare strange quark stars and (normal) strange quark-matter stars, those possessing a baryon (electron-supported) crust, are hypothesized as good candidates to explain the properties of a set of peculiar stellar sources such as the enigmatic X-ray source RX J1856.5-3754, some pulsars such as PSR B1828-11 and PSR B1642-03, and the anomalous X-ray pulsars and soft γ-ray repeaters. In the MIT bag model, quarks are treated as a degenerate Fermi gas confined to a region of space having a vacuum energy density B bag (the Bag constant). In this note, we modify the MIT bag model by including the electromagnetic interaction. We also show that this version of the MIT model implies the anisotropy of the bag pressure due to the presence of the magnetic field. The equations of state of the degenerate quarks gases are studied in the presence of ultra strong magnetic fields. The behavior of a system made up of quarks having (or not) anomalous magnetic moment is reviewed. A structural instability is found, which is related to the anisotropic nature of the pressures in this highly magnetized matter. The conditions for the collapse of this system are obtained and compared to a previous model of neutron stars that is built on a neutron gas having anomalous magnetic moment.

The neutrino emissivity of strange stars with ultra strong magnetic field

The effect of a strong magnetic field on the dominant neutrino emissivity in strange stars is investigated. In an ultra strong magnetic field, there exists an enhanced neutrino emission because the charged particles are confined to the lowest Landau level. The results show that the neutrino emissivity is proportional to T 5 instead of conventional T 6, which implies more rapid cooling behavior in magnetars than usual strange stars.

COLLAPSE/FLATTENING OF NUCLEONIC BAGS IN ULTRA-STRONG MAGNETIC FIELD

It is shown explicitly using MIT bag model that in presence of ultra-strong magnetic fields, a nucleon either flattens or collapses in the direction transverse to the external magnetic field in the classical or quantum mechanical picture respectively. Which gives rise to some kind of mechanical instability. Alternatively, it is argued that the bag model of confinement may not be applicable in this strange situation.

Neutron capture reactions in strong magnetic fields of magnetars

The statistical model is employed to investigate $(n,\ensuremath{\gamma})$ reactions in ultrastrong magnetic fields relevant for supernovae and neutron stars. The predominant mechanisms are argued to correspond to modifications of nuclear level densities and $\ensuremath{\gamma}$-transition energies due to interactions of the field with magnetic moments of nuclei. The density of states reflects the nuclear structure and results in oscillations of reaction cross sections as a function of the field strength, while magnetic interaction energy enhances radiative neutron capture process.

Magnetoplasmons of the two-dimensional electron system in a parabolic channel over liquid helium

Magnetoplasmon waves of the nondegenerate two-dimensional electron system confined in a parabolic channel over liquid helium are studied in the ultra quantum limit (only the lowest spin-split Landau level is occupied) and strong magnetic fields. It is shown that the dispersion relations and spatial structures have the characteristic scale ℓ T= 2k B T/m ∗Ω 2 ⪢ℓ 0 , where Ω is the confinement frequency and ℓ 0 is the magnetic length. We find a rich spectrum of low-frequency excited acoustical modes whose phase velocities exhibit anticrossings as a function of the metal gate distance d, for d⪡ℓ T . It is shown that appearance of the anticrossings has essentially a quantum nature combined with the effect of the electron–electron interaction. In order to be able to discuss the conditions to detect the modes we determine the mode dissipation and compare our results with experimental data.

Mechanism of high-energy electron production in a laser plasma

A mechanism of high-energy electron production in the interaction of high-intensity short laser pulses with a solid target is proposed and analysed. The theoretical dependences of fast-electron kinetic energy on the parameters of laser radiation and target material are given. The effect of ionisation of the target material is considered. The generation of ultrastrong magnetic fields in the laser plasma is shown to play the key part in the formation, transfer, and acceleration of electron beams. This results in the production of vortex electric fields accelerating electrons. The theoretical dependences yield well-proved limits for the electron energy and are in good agreement with the results of experiments performed on high-intensity laser setups, including the results obtained with participation of the author.

Investigation of magnetic properties in strong and ultrastrong magnetic fields using the single-turn coil technique: new phenomena in intermetallic compounds and rare-earth zircons

Abstract Magnetic anomalies in rare-earth zircons RXO 4 (X=V, As, P; R-rare-earth ion), which are caused by the crossing of the lowest-lying energy levels of the van Vleck paramagnets, have been studied at different field sweep rates and different cryogenic temperatures. These anomalies occur at about 50 T for PrVO 4 and at about 30 T for TmPO 4 . Recent magnetization measurements of the intermetallic compounds RMn 2 Ge 2 (R=Gd, Tb, Dy, Ho, Er, Y) reveal new magnetic phase transitions for some R in strong magnetic fields up to 150 T.

MAGNETIC FIELDS AND VACUUM POLARIZATION AT THE PLANCK ERA

The one-loop effective action describing polarization of the vacuum due to virtual electron-positron pairs in the Maxwell theory of electromagnetism was obtained by Heisenberg and Euler, in the limit of a background field that is constant on the scale of the electron Compton-wavelength. The case of vanishing electric field and constant, ultra-strong magnetic field B≫Bc, where [Formula: see text], yields a configuration whose energy density is less than that of the equivalent radiation field, suggesting why a magnetic field may be present in the early Universe back to the Planck era. For there is a similar but larger effect, allowing a "ferromagnetic" Yang–Mills vacuum state, in the grand-unified theory at temperatures [Formula: see text], analyzed by Skalozub. Some further aspects of ultra-strong magnetic fields are discussed vis-à-vis the origin of the Galactic field B g .

Screenedαdecay in dense astrophysical plasmas and superstrong magnetic fields

This paper shows that ultrastrong magnetic fields (such as those of magnetars) and dense astrophysical plasmas can reduce the half-life of $\ensuremath{\alpha}$-decaying nuclei by many orders of magnitude. In such environments, the conventional Geiger-Nuttall law is modified so that all relevant half-lives are shifted to dramatically lower values.

Cyclotron mechanism of electron acceleration in subpicosecond laser plasma

The effect of ultrastrong magnetic fields generated in a relativistic-intensity subpicosecond laser plasma on the acceleration of fast electrons was studied. It is shown that resonance electrons can continuously accumulate energy from the circularly polarized laser field in the presence of a longitudinal magnetic field. For the linear polarization and a transverse magnetic field, energy accumulation has a pulse-periodic character, and the electron trajectories correspond to electron rotation in the Larmor orbit in a quasi-stationary magnetic field, while the energy strongly oscillates. In both cases, electron energy may attain values higher than 100 MeV for intensities of 1020 W/cm2.

New Evidence of Proton-Cyclotron Resonance in a Magnetar Strength Field from SGR 1806−20

A great deal of evidence has recently been gathered in favor of the picture that Soft Gamma Repeaters and Anomalous X-Ray Pulsars are powered by ultra-strong magnetic fields (B greater than 10(exp 14) G; i.e. magnetars). Nevertheless, present determination of the magnetic field in such magnetar candidates has been indirect and model dependent. A key prediction concerning magnetars is the detection of ion cyclotron resonance features, which would offer a decisive diagnostic of the field strength. Here we present the detection of a 5 keV absorption feature in a variety of bursts from the Soft Gamma Repeater SGR 1806-20, confirming our initial discovery and establishing the presence of the feature in the source's burst spectra. The line feature is well explained as proton cyclotron resonance in an ultra-strong magnetic field, offering a direct measurement of SGR 1806-20's magnetic field (B approx. 10(exp 15) G) and a clear evidence of a magnetar. Together with the source's spin-down rate, the feature also provides the first measurement of the gravitational redshift, mass and radius of a magnetar.

Radiative decay of the massive neutrino in magnetized plasma

Within the framework of one-loop approximation of the standard model, the probability of radiative decay of the massive Dirac neutrino νi → νj + γ in a dense medium was calculated in an intensive, external, constant magnetic field. It was found that in the case of a degenerate electron gas (important for astrophysical applications), the decay rate essentially increases due to the influence of an ultrastrong magnetic field.

Using self-generated harmonics as a diagnostic of high intensity laser-produced plasmas

The interaction of high intensity laser pulses (up to I∼1020 W cm−2) with plasmas can generate very high order harmonics of the laser frequency (up to the 75th order have been observed). Measurements of the properties of these harmonics can provide important insights into the plasma conditions which exist during such interactions. For example, observations of the spectrum of the harmonic emission can provide information of the dynamics of the critical surface as well as information on relativistic non-linear optical effects in the plasma. However, most importantly, observations of the polarization properties of the harmonics can provide a method to measure the ultra-strong magnetic fields (greater than 350 MG) which can be generated during these interactions. It is likely that such techniques can be scaled to provide a significant amount of information from experiments at even higher intensities.