Pulsars and Magnetars

Mereghetti, S.

doi:10.1007/s13538-013-0137-y

Cited by 36 publications

(42 citation statements)

References 194 publications

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“…They are commonly called magnetars, because they are thought to have super-strong magnetic fields (10 14 −10 15 G). For recent reviews see Woods & Thompson (2006) and Mereghetti (2008Mereghetti ( , 2013. Two main models have been proposed to explain the observational data; the classical magnetar model (e.g., Thompson & Duncan 1993 and the fallback disk one (Chatterjee et al 2000;Alpar 2001).…”

Section: Introductionmentioning

confidence: 99%

Spectral formation in a radiative shock: application to anomalous X-ray pulsars and soft gamma-ray repeaters

Kylafis

Trümper

Ertan

2014

A&A

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Context. In the fallback disk model for the persistent emission of anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs), the hard X-ray emission arises from bulk-and thermal Comptonization of bremsstrahlung photons, which are generated in the accretion column. The relatively low X-ray luminosity of these sources implies a moderate transverse optical depth to electron scattering, with photons executing a small number of shock crossings before escaping sideways. Aims. We explore the range of spectral shapes that can be obtained with this model and characterize the most important parameter dependencies. Methods. We use a Monte Carlo code to study the crisscrossing of photons in a radiative shock in an accretion column and compute the resulting spectrum. Results. As expected, high-energy power-law X-ray spectra are produced in radiative shocks with photon-number spectral index Γ > ∼ 0.5. We find that the required transverse optical depth is 1 < ∼ τ ⊥ < ∼ 7. Such spectra are observed in low-luminosity X-ray pulsars. Conclusions. We demonstrate here with a simple model that Compton upscattering in the radiative shock in the accretion column can produce hard X-ray spectra similar to those seen in the persistent and transient emission of AXPs and SGRs. In particular, one can obtain a high-energy power-law spectrum, with photon-number spectral-index Γ ∼ 1 and a cutoff at 100−200 keV, with a transverse Thomson optical depth of ∼5, which is shown to be typical in AXPs/SGRs.

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Section: Introductionmentioning

confidence: 99%

Spectral formation in a radiative shock: application to anomalous X-ray pulsars and soft gamma-ray repeaters

Kylafis

Trümper

Ertan

2014

A&A

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“…The NPB can also be important in X-ray superbursts in accreting NSs (e.g. [16]), and in thermal evolution of magnetars [17], as well as in massive cooling white dwarfs.…”

Section: Discussionmentioning

confidence: 99%

An effective potential for electron-nucleus scattering in neutrino-pair bremsstrahlung in neutron star crust

Ofengeim

Kaminker

Yakovlev

2015

J. Phys.: Conf. Ser.

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Abstract.We derive an analytic approximation for the emissivity of neutrino-pair bremsstrahlung (NPB) due to scattering of electrons by atomic nuclei in a neutron star (NS) crust of any realistic composition. The emissivity is expressed through generalized Coulomb logarithm by introducing an effective potential of electron-nucleus scattering. In addition, we study the conditions at which NPB in the crust is affected by strong magnetic fields and outline the main effects of the fields on neutrino emission in NSs. The results can be used for modelling of many phenomena in NSs, such as cooling of young isolated NSs, thermal relaxation of accreting NSs with overheated crust in soft X-ray transients and evolution of magnetars.

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“…According to the most popular point of view, anomalous X-ray pulsars (AXPs) and soft gamma repeaters (SGRs) [38][39][40][41][42] are magnetars. For these objects, the estimate (1) most often (although not always) gives B ∼ 10 14 G, but in order to explain their energy balance, magnetic fields reaching up to B ∼ 10 16 -10 17 G in the core at the birth of the star are considered (see [43] and references therein).…”

Section: Magnetic Fieldsmentioning

confidence: 99%

“…Indeed, for a characteristic poloidal component B pol of a neutronstar magnetic field to be stable, a toroidal component B tor must be present, such that, by order of magnitude, B pol B tor 10 16 G B pol /(10 13 G) [47]. Meanwhile, there is increasing evidence for the absence of a clear distinction between AXPs and SGRs [48], as well as between these objects and other neutron stars [41,42,49]. There has even appeared the paradoxical name "a lowfield magnetar," applied to those AXPs and SGRs that have B ≪ 10 14 G (e.g., [50,51], and references therein).…”

Section: Magnetic Fieldsmentioning

confidence: 99%

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Atmospheres and radiating surfaces of neutron stars

Potekhin¹

2014

Phys.-Usp.

109

129

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The early 21st century witnesses a dramatic rise in the study of thermal radiation of neutron stars. Modern space telescopes have provided a wealth of valuable information which, when properly interpreted, can elucidate the physics of superdense matter in the interior of these stars. This interpretation is necessarily based on the theory of formation of neutron star thermal spectra, which, in turn, is based on plasma physics and on the understanding of radiative processes in stellar photospheres. In this paper, the current status of the theory is reviewed with particular emphasis on neutron stars with strong magnetic fields. In addition to the conventional deep (semi-infinite) atmospheres, radiative condensed surfaces of neutron stars and "thin" (finite) atmospheres are considered.

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Pulsars and Magnetars

Cited by 36 publications

References 194 publications

Spectral formation in a radiative shock: application to anomalous X-ray pulsars and soft gamma-ray repeaters

Spectral formation in a radiative shock: application to anomalous X-ray pulsars and soft gamma-ray repeaters

An effective potential for electron-nucleus scattering in neutrino-pair bremsstrahlung in neutron star crust

Atmospheres and radiating surfaces of neutron stars

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