A model of nonthermal radiation from accreting X-ray pulsars

Leung, P.; Cheng, K. S.; Fung, P. C. W.

doi:10.1086/172747

Cited by 2 publications

(2 citation statements)

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“…The process of particle acceleration in rapidly rotating magnetospheres, and the accompanying radiation, have been discussed extensively (e.g. Usov 1988, 1993; Leung, Cheng & Fung 1993; Ikhsanov & Biermann 2006). The lack of substantial mass accretion on to the surface of the white dwarf in AE Aqr (e.g.…”

Section: X‐ray Emission In Ae Aqrmentioning

confidence: 99%

X-ray characteristics and the spectral energy distribution of AE Aquarii

Oruru

Meintjes

2012

Monthly Notices of the Royal Astronomical Society

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Using data from contemporaneous observations with Chandra and Swift, it is shown that the X‐ray emission below 10 keV is predominantly thermal, characterized by flares and emission lines and dominated by the soft component. The Chandra and Swift X‐ray spectra (EX≤ 10 keV) can be reproduced by multicomponent thermal emission models with a time‐averaged X‐ray luminosity of LX∼ 1031 erg s−1. The pulsed 33‐s soft X‐ray emission below 10 keV is confirmed in both the Chandra and Swift data sets. The epoch of pulse maximum of the 33‐s white dwarf spin period is consistent with the recently derived ephemeris based upon Suzaku measurements. The recently detected Suzaku hard X‐ray component above 10 keV shows a non‐thermal power‐law nature, with a photon index of Γ∼ 1.2, possibly the result of synchrotron emission of high‐energy electrons in the white dwarf magnetosphere. The hard X‐ray luminosity of LX,hard≤ 5 × 1030 erg s−1 also constitutes κ∼ 0.1 per cent of the total spin‐down luminosity of the white dwarf. This places AE Aquarii in the same category as young spin‐powered pulsars between 2 and 20 keV. Additionally, it is shown that electrons can be accelerated to energies in excess of 10 TeV outside the light cylinder radius, providing interesting possibilities for VHE‐TeV follow‐up observations. The X‐ray emission below EX≤ 10 keV, on the other hand, is explained in terms of plasma heating at the magnetospheric radius, the result of the dissipation of gravitational potential energy. It is found that a conversion efficiency of α∼ 0.01 is sufficient to heat the plasma at the magnetospheric boundary to temperatures kT≤ 10 keV, sufficient to drive the X‐ray emission below 10 keV. Only a small fraction (β∼ 0.3 per cent) of the mass flow at the magnetospheric radius eventually accretes on to the surface of the white dwarf, emphasizing the very effective magnetospheric propeller process in the system.

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Section: X‐ray Emission In Ae Aqrmentioning

confidence: 99%

X-ray characteristics and the spectral energy distribution of AE Aquarii

Oruru

Meintjes

2012

Monthly Notices of the Royal Astronomical Society

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“…where l 8 is the typical size of the gap in units of 10 8 cm and s 8 is a curvature radius of the local magnetic field line in units of 10 8 cm. For simplicity, these two parameters are assumed to be equal to ∼ r 0 (for a similar assumption, see Cheng et al 1992;Leung et al 1993).…”

Section: Production Mechanism Of Non-thermal Radiation Spectramentioning

confidence: 99%

Non-thermal emissions from accreting X-ray binary pulsars

Zhang¹,

Jin²,

Dong³

2014

Res. Astron. Astrophys.

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We study non-thermal emissions from cascade processes in accreting X-ray binary pulsars. In the framework of the magnetospheric gap model, we consider three photon fields, which are respectively from the polar cap of a pulsar, its surrounding accretion disk and a massive companion star with a circumstellar disk, to shield the gap. The gap-accelerated ultra-relativistic electrons emit high-energy photons via curvature radiation and an inverse Compton scattering process, in which part of these high-energy photons absorbed by interactions with the surrounding photon fields can facilitate the following electromagnetic cascades. We first carry out numerical calculations of the cascade processes in order to obtain the predicted emission spectra. As an example, we subsequently apply this model to reproduce observations of LS I +61 • 303. We find that the results can fit observations ranging from hard X-ray to γ-ray bands. In particular, they can explain the spectral cutoff feature at a few GeV. Finally, we suggest that the emissions detected by the Fermi Large Area Telescope from X-ray binary pulsars originate in the magnetosphere region of the pulsar.

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A model of nonthermal radiation from accreting X-ray pulsars

Cited by 2 publications

References 0 publications

X-ray characteristics and the spectral energy distribution of AE Aquarii

X-ray characteristics and the spectral energy distribution of AE Aquarii

Non-thermal emissions from accreting X-ray binary pulsars

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