One- and two-photon Compton scattering in strong magnetic fields

Bussard, R. W.; Alexander, Shishkin; Mészáros, P.

doi:10.1103/physrevd.34.440

Cited by 55 publications

(67 citation statements)

References 12 publications

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“…The full details of the ST cross section formalism is described in Gonthier et al (2014); they supplant the spin-averaged Johnson & Lippmann (1949, hereafter JL) cross section formalism found in previous treatments (e.g. Herold 1979;Daugherty & Harding 1986;Bussard, Alexander & Mészáros 1986).…”

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confidence: 65%

Resonant Inverse Compton Scattering Spectra from Highly Magnetized Neutron Stars

Wadiasingh

Baring

Gonthier

et al. 2018

ApJ

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Hard, non-thermal, persistent pulsed X-ray emission extending between 10 keV and ∼ 150 keV has been observed in nearly ten magnetars. For inner-magnetospheric models of such emission, resonant inverse Compton scattering of soft thermal photons by ultra-relativistic charges is the most efficient production mechanism. We present angle-dependent upscattering spectra and pulsed intensity maps for uncooled, relativistic electrons injected in inner regions of magnetar magnetospheres, calculated using collisional integrals over field loops. Our computations employ a new formulation of the QED Compton scattering cross section in strong magnetic fields that is physically correct for treating important spindependent effects in the cyclotron resonance, thereby producing correct photon spectra. The spectral cut-off energies are sensitive to the choices of observer viewing geometry, electron Lorentz factor, and scattering kinematics. We find that electrons with energies < ∼ 15 MeV will emit most of their radiation below 250 keV, consistent with inferred turnovers for magnetar hard X-ray tails. More energetic electrons still emit mostly below 1 MeV, except for viewing perspectives sampling field line tangents. Pulse profiles may be singly-or doubly-peaked dependent upon viewing geometry, emission locale, and observed energy band. Magnetic pair production and photon splitting will attenuate spectra to hard X-ray energies, suppressing signals in the Fermi-LAT band. The resonant Compton spectra are strongly polarized, suggesting that hard X-ray polarimetry instruments such as X-Calibur, or a future Compton telescope, can prove central to constraining model geometry and physics.

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confidence: 65%

Resonant Inverse Compton Scattering Spectra from Highly Magnetized Neutron Stars

Wadiasingh

Baring

Gonthier

et al. 2018

ApJ

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“…For cyclotron features produced in hard incident continua (as in this investigation), the work led by the groups of Isemberg, Lamb, & Wang (1997 ;Lamb et al 1989 ;Wang et al 1989 ;Wang, Wasserman, & Salpeter 1988 ;Wasserman & Salpeter 1980 ;Ventura, Nagel, & 1979) and of Me sza ros Alexander, & Me sza ros Me sza ros, Bussard 1989 ;Bussard, Alexander, & 1986 ; Me sza ros & Nagel 1985a& Nagel , 1985bNagel 1981aNagel , 1981b Me sza ros depict the state of the art calculations and are most closely related to the models produced here. Isenberg et al (1997) o †er a thorough review of the general problem of cyclotron line formation with regard to the line photon transfer.…”

Section: Introductionmentioning

confidence: 83%

Cyclotron Line Features from Near‐critical Magnetic Fields: The Effect of Optical Depth and Plasma Geometry

Araya

Harding

1999

ApJ

132

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A detailed analytical study of the relativistic proÐle for magnetic Compton scattering is performed and use is made of Monte Carlo methods to construct a numerical scheme for the production of relativistic theoretical cyclotron spectra from internally irradiated scattering atmospheres in the low-density/highÐeld regime. The cross section includes natural line widths, and the Monte Carlo implementation allows for spatial di †usion of photons in arbitrary geometries while accounting for relativistic angular redistribution. Detailed consideration of "" Raman-Landau ÏÏ scattering permits photon spawning from up to fourth harmonic photons. This scheme is utilized to make speciÐc predictions on the e †ect of geometry and optical depth on the formation of cyclotron lines in hard incident continua. Even if the injection is isotropic, a strongly anisotropic radiation Ðeld ensues at relatively low optical depths. The scattering proÐles at large angles and low Ðelds are highly asymmetric and peak at the relativistic energy cuto †, not necessarily at the resonant energy. Higher harmonic features in general bear little resemblance to the fundamental even at high Ðelds (B D 10 TG), and slabs yield the deepest features, while cylinders present the widest lines at small angles. Moreover, the fundamental line photons in slab scattering regions tend to redistribute to the line wings from all angles, producing fairly broad emission line wings at small angles. Higher optical depths at those angles hampers such redistribution in cylindrical geometries.

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“…The redistribution matrix elements S i j are calculated using the equations for differential scattering cross sections from Bussard et al (1986) derived in a fully relativistic approximation. Thus the second-order Doppler effect and the non-harmonicity of the electron Landau levels are included in our calculations.…”

Section: Discussionmentioning

confidence: 99%

Luminosity-dependent changes of the cyclotron line energy and spectral hardness in Cepheus X-4

Vybornov

Klochkov

Gornostaev

et al. 2017

A&A

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Context. X-ray spectra of accreting pulsars are generally observed to vary with their X-ray luminosity. In particular, the hardness of the X-ray continuum is found to depend on luminosity. In a few sources, the correlation between the energy of the cyclotron resonance scattering feature (CRSF) and the luminosity is clear. Different types (signs) of the correlation are believed to reflect different accretion modes. Aims. We analyse two NuSTAR observations of the transient accreting pulsar Cep X-4 during its 2014 outburst. Our analysis is focused on a detailed investigation of the dependence of the CRSF energy and of the spectral hardness on X-ray luminosity, especially on short timescales. Methods. To investigate the spectral changes as a function of luminosity within each of the two observations, we used the intrinsic variability of the source on the timescale of individual pulse cycles (tens of seconds) , the so-called pulse-to-pulse variability. Results. We find that the NuSTAR spectrum of Cep X-4 contains two CRSFs: the fundamental line at~30 keV and its harmonic at~55 keV. We find for the first time that the energy of the fundamental CRSF increases and the continuum becomes harder with increasing X-ray luminosity not only between the two observations, that is, on the long timescale, but also within an individual observation, on the timescale of a few tens of seconds. We investigate these dependencies in detail including their non-linearity. We discuss a possible physical interpretation of the observed behaviour in the frame of a simple one-dimensional model of the polar emitting region with a collisionless shock formed in the infalling plasma near the neutron star surface. With this model, we are able to reproduce the observed variations of the continuum hardness ratio and of the CRSF energy with luminosity.

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One- and two-photon Compton scattering in strong magnetic fields

Cited by 55 publications

References 12 publications

Resonant Inverse Compton Scattering Spectra from Highly Magnetized Neutron Stars

Resonant Inverse Compton Scattering Spectra from Highly Magnetized Neutron Stars

Cyclotron Line Features from Near‐critical Magnetic Fields: The Effect of Optical Depth and Plasma Geometry

Luminosity-dependent changes of the cyclotron line energy and spectral hardness in Cepheus X-4

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