Plasma Physics of Accreting Neutron Stars

Ghosh, Pranab; Lamb, Frederick K.

doi:10.1007/978-94-011-3536-8_20

Cited by 48 publications

(12 citation statements)

References 133 publications

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“…This is an order of L BB ] (R NS /r m )2 D 1034 magnitude below the luminosity of the soft component adopted by & Nagel (1985a& Nagel ( , 1985b. This discrepMe sza ros ancy can be reduced if, as shown in Figure 9, the accretion disk signiÐcantly distorts the shape of the magnetosphere (Ghosh & Lamb 1991), reducing the magnetospheric radius to the value where / is in the range 0.1È0.5 (see, r m , /R A , e.g., Ghosh & Lamb 1991 ;Burderi et al 1998). This raises the luminosity of the soft component up to 4 ] 1034È1036 ergs s~1.…”

Section: Discussionmentioning

confidence: 99%

The 0.1–100 keV Spectrum of Centaurus X‐3: Pulse Phase Spectroscopy of the Cyclotron Line and Magnetic Field Structure

Burderi

Salvo

Robba

et al. 2000

ApJ

114

120

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We report spectral and temporal analysis of the X-ray pulsar Centaurus X-3 out of eclipse observed by BeppoSAX. The broadband spectrum (0.12È100 keV) is well described by an absorbed power law modiÐed by a high-energy rollover at D14 keV (e-folding energy D8 keV) plus an iron emission line at D6.7 keV. A soft excess below 1 keV is also present. Interpreted as a blackbody (kT^0.1 keV), it corresponds to 58% of the total unabsorbed Ñux. This component seems to originate from reprocessing of the primary radiation by an opaque shell located at the magnetosphere. An absorption feature at D30 keV is also present. Interpreted as a cyclotron line, after correction for gravitational redshift, this corresponds to a surface magnetic Ðeld of D3.5 ] 1012 G. Phase-resolved spectroscopy reveals a variation by about 8 keV of the cyclotron resonance energy along the pulse proÐle. In particular, the line energy decreases from D36 to D28 keV along the peak, starting from the ascent. The asymmetric variations of the cyclotron line energy can be explained by assuming an o †set of the dipolar magnetic Ðeld with respect to the neutron star center. The spectral results are discussed in terms of emission from magnetic caps, where Comptonization of soft photons occurs. The soft photons could come from either magnetically resonant double Compton scattering or from illumination of the polar cap by the primary radiation reprocessed at the magnetospheric surface, a feedback mechanism similar to that proposed for the formation of black hole spectra.

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Section: Discussionmentioning

confidence: 99%

The 0.1–100 keV Spectrum of Centaurus X‐3: Pulse Phase Spectroscopy of the Cyclotron Line and Magnetic Field Structure

Burderi

Salvo

Robba

et al. 2000

ApJ

114

120

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“…The relation between the magnetospheric radius and the magnetic R m Ðeld strength is R m \ 4.3 ] 103/k 30 4@7 R 6 2@7 L 37 2@7 v2@7m1@7 km (see, e.g., Burderi et al 1998), where / D 0.5 is a correction factor for the radius when an accretion disk is Alfven present (Ghosh & Lamb 1991), is the magnetic moment k 30 in units of 1030 G cm3, is the neutron star radius, in R 6 R NS , units of 106 cm, is the intrinsic luminosity of the Com-L 37 ptonized component in units of 1037 ergs s~1, v is the ratio between the observed luminosity and the total gravitational potential energy released per second by the accreting matter, and m is the neutron star mass in units of solar mass. Adopting and m \ 1.4 (typical for a neutron R 6 \ 1 star), v D 1, and we can Ðnd a magnetic Ðeld R m \ R W , strength for each interval.…”

Section: Possible Presence Of a Magnetic Field Of D4 ] 1010 Gmentioning

confidence: 99%

A Hard Tail in the X‐Ray Broadband Spectrum of Circinus X‐1 at the Periastron: A Peculiar Z Source

Iaria

Burderi

Salvo

et al. 2001

ApJ

100

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We report on the spectral analysis of the peculiar source Cir X-1 observed by the BeppoSAX satellite when the X-ray source was near the periastron. A Ñare lasting D6 ] 103 s is present at the beginning of the observation. The luminosity during the persistent emission is 1 ] 1038 ergs s~1, while during the Ñare it is 2 ] 1038 ergs s~1. We produced broadband (0.1È100 keV) energy spectra during the Ñare and the persistent emission. At low energies the continuum is well Ðtted by a model consisting of Comptonization of soft photons, with a temperature of D0.4 keV, by electrons at a temperature of D1 keV. After the Ñare, a power-law component with photon index D3 is dominant at energies higher than 10 keV. This component contributes D4% of the total luminosity. During the Ñare its addition is not statistically signiÐcant. An absorption edge at D8.4 keV, with optical depth D1, corresponding to the K edge of Fe XXIIIÈFe XXV, and an iron emission line at 6.7 keV are also present. The iron-line energy is in agreement with the ionization level inferred from the absorption edge. The hydrogen column deduced from the absorption edge is D1024 cm~2, 2 orders of magnitude larger than the low-energy absorption measured in this source. We calculated the radius of the region originating the Comptonized seed photons, km. We propose a scenario where (the Wien radius) is the inner disk radius, a R W D 150 R W highly ionized torus surrounds the accretion disk, and a magnetosphere is present up to The R W . absorption edge and the emission line could originate in the photoionized torus, while the Comptonized component originates in an inner region of the disk.

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“…Using (47), (51), and (52) and analogy with Maxwell's equations, we get the gravitoelectromagnetic field equations [90]:…”

Section: Rotation Effects Andmentioning

confidence: 99%

Physical Environment of Accreting Neutron Stars

Wang

2016

Advances in Astronomy

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Neutron stars (NSs) powered by accretion, which are known as accretion-powered NSs, always are located in binary systems and manifest themselves as X-ray sources. Physical processes taking place during the accretion of material from their companions form a challenging and appealing topic, because of the strong magnetic field of NSs. In this paper, we review the physical process of accretion onto magnetized NS in X-ray binary systems. We, firstly, give an introduction to accretion-powered NSs and review the accretion mechanism in X-ray binaries. This review is mostly focused on accretion-induced evolution of NSs, which includes scenario of NSs both in high-mass binaries and in low-mass systems.

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Plasma Physics of Accreting Neutron Stars

Cited by 48 publications

References 133 publications

The 0.1–100 keV Spectrum of Centaurus X‐3: Pulse Phase Spectroscopy of the Cyclotron Line and Magnetic Field Structure

The 0.1–100 keV Spectrum of Centaurus X‐3: Pulse Phase Spectroscopy of the Cyclotron Line and Magnetic Field Structure

A Hard Tail in the X‐Ray Broadband Spectrum of Circinus X‐1 at the Periastron: A Peculiar Z Source

Physical Environment of Accreting Neutron Stars

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