Pulsars: Progress, Problems and Prospects

Arons, Jonathan

doi:10.48550/arxiv.0708.1050

“…Alternatively, the TeV photons can be produced as a result of π 0 → γ + γ decay, with π 0 being produced when the relativistic protons from the pulsar wind interact with the ambient matter [97]. If confirmed, the latter mechanism may provide the long-sought observational evidence for the elusive proton component in the pulsar wind [98].…”

Section: Luminosities and Spectramentioning

confidence: 99%

Pulsar Wind Nebulae in the Chandra Era

Kargaltsev

¹

,

Pavlov²

2008

AIP Conference Proceedings

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Pulsar winds shocked in the ambient medium produce spectacular nebulae observable from the radio through gamma-rays. The shape and the spectrum of a pulsar wind nebula (PWN) depend on the angular distribution, magnetization and energy spectrum of the wind streaming from the pulsar magnetosphere, as well as on the pulsar velocity and the properties of the ambient medium. The advent of Chandra, with its unprecedented angular resolution and high sensitivity, has allowed us not only to detect many new PWNe, but also study their spatial and spectral structure and dynamics, which has significantly advanced our understanding of these objects. Here we overview recent observational results on PWNe, with emphasis on Chandra observations.Comment: 15 pages, 5 tables, 10 figures. To appear in the proceedings of "40 Years of Pulsars: Millisecond Pulsars, Magnetars, and More", August 12-17, 2007, McGill University, Montreal, Canada. Corrected typos in Table

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“…There still exists a gap between analytical acceleration models and numerical simulations or observation data of perpendicular shocks, as very large amplitudes for the magnetic turbulence are needed to enable multiple scatterings of the particles in the shock and to form the observed energy spectra (Arons 2007). Since the acceleration process cannot be explained by a simple model, Arons (2007) suggested a mixture of diffusive Fermi acceleration and an additional acceleration process, where heavy ions play a major role.…”

Section: Introductionmentioning

confidence: 99%

“…There still exists a gap between analytical acceleration models and numerical simulations or observation data of perpendicular shocks, as very large amplitudes for the magnetic turbulence are needed to enable multiple scatterings of the particles in the shock and to form the observed energy spectra (Arons 2007). Since the acceleration process cannot be explained by a simple model, Arons (2007) suggested a mixture of diffusive Fermi acceleration and an additional acceleration process, where heavy ions play a major role. The latter process provides a mechanism to produce a broad energy range in plasmas, where pairs dominate by number and where ions are energetically dominant, explaining the observed range of optical, X-and γ-radiation in Pulsar Wind Nebulae, but still the spectra are not all in agreement with observations.…”

Section: Introductionmentioning

confidence: 99%

Acceleration in Perpendicular Relativistic Shocks for Plasmas Consisting of Leptons and Hadrons

Stockem¹,

Fiúza²,

Fonseca

³

et al. 2012

ApJ

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We investigate the acceleration of light particles in perpendicular shocks for plasmas consisting of a mixture of leptonic and hadronic particles. Starting from the full set of conservation equations for the mixed plasma constituents, we generalize the magnetohydrodynamical jump conditions for a multi-component plasma, including information about the specific adiabatic constants for the different species. The impact of deviations from the standard model of an ideal gas is compared in theory and particle-in-cell simulations, showing that the standard-MHD model is a good approximation. The simulations of shocks in electron-positron-ion plasmas are for the first time multi-dimensional, transverse effects are small in this configuration and 1D simulations are a good representation if the initial magnetization is chosen high. 1D runs with a mass ratio of 1836 are performed, which identify the Larmor frequency ω ci as the dominant frequency that determines the shock physics in mixed component plasmas. The maximum energy in the non-thermal tail of the particle spectra evolves in time according to a power-law ∝ t α with α in the range 1/3 < α < 1, depending on the initial parameters. A connection is made with transport theoretical models by Drury (1983) and Gargaté & Spitkovsky (2011), which predict an acceleration time ∝ γ and the theory for small wavelength scattering by Kirk & Reville (2010), which predicts a behavior rather as ∝ γ 2 . Furthermore, we compare different magnetic field orientations with B 0 inside and out of the plane, observing qualitatively different particle spectra than in pure electron-ion shocks.

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“…In the standard pulsar model (Goldreich & Julian 1969), the magnetosphere is considered to be 'force-free' in that the electromagnetic energy density dominates all other dissipative forces and that radiative emission has a negligible effect on the spin-down rate (Arons 2007). Instead, the configuration of the magnetosphere, based on the polar cap cascade zone and the current density within the open field lines, and its change over time dictates the pulsar spin-down rate (Timokhin 2006;Arons 2007;Timokhin 2010).…”

Section: Standard Model Assumptionsmentioning

confidence: 99%

“…In the standard pulsar model (Goldreich & Julian 1969), the magnetosphere is considered to be 'force-free' in that the electromagnetic energy density dominates all other dissipative forces and that radiative emission has a negligible effect on the spin-down rate (Arons 2007). Instead, the configuration of the magnetosphere, based on the polar cap cascade zone and the current density within the open field lines, and its change over time dictates the pulsar spin-down rate (Timokhin 2006;Arons 2007;Timokhin 2010). Recently, Timokhin (2010) speculates that the magnetospheres of some pulsars can have several quasi-stable states with different configurations and that the switching of the magnetosphere between these states can result in the observed mode changes and nulls.…”

Section: Standard Model Assumptionsmentioning

confidence: 99%

A Non-Radial Oscillation Model for Pulsar State Switching

Rosen¹,

McLaughlin²,

Thompson³

2011

ApJ

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Pulsars are unique astrophysical laboratories because of their clock-like timing precision, providing new ways to test general relativity and detect gravitational waves. One impediment to high-precision pulsar timing experiments is timing noise. Recently Lyne et al. (2010) showed that the timing noise in a number of pulsars is due to quasi-periodic fluctuations in the pulsars' spin-down rates and that some of the pulsars have associated changes in pulse profile shapes. Here we show that a non-radial oscillation model based on asteroseismological theory can explain these quasi-periodic fluctuations. Application of this model to neutron stars will increase our knowledge of neutron star emission and neutron star interiors and may improve pulsar timing precision.

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Pulsars: Progress, Problems and Prospects

Cited by 5 publications

References 94 publications

Pulsar Wind Nebulae in the Chandra Era

Pulsar Wind Nebulae in the Chandra Era

Acceleration in Perpendicular Relativistic Shocks for Plasmas Consisting of Leptons and Hadrons

A Non-Radial Oscillation Model for Pulsar State Switching

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