Annihilation radiation from a power-law distributed electron-positron plasma on the ground Landau level

the case of low magnetic fields

A. D. Kaminker, George Pavlov, P. G. Mamradze

Research output: Contribution to journalArticle

Abstract

Intensity, polarization, and cooling rate of the two-photon annihilation radiation are studied in detail in the case of one-dimensional power-law distributions of electrons and positrons, assuming that they occupy the ground Landau level in a strong magnetic field B∼1010-1012 G. Simple analytical expressions for limiting cases are obtained and results of numerical calculations of radiation characteristics are presented. Power-law e± distributions η± ∝ ε±-k are shown to generate power-law spectra of the annihilation radiation at E≫mc2 and E≪mc2, with indices depending on the direction of radiation. The annihilation spectra at θ{symbol}=0 show the largest blue-shifts of their maxima and the hardest high-energy tails I(E≫mc2, θ{symbol}=0)∝E-(k-1). The blue-shifts reduce, and the hard tials steepen, with increasing θ{symbol}. At θ{symbol}>(2 mc2/E)1/2 the slopes of the high-energy tails rapidly transform to that at θ{symbol}=π2, I(E≫mc2, θ{symbol}=π/2)∝E-(2 k+3). The direction-integrated spectra S(E) also display the power-law tials at low and high energies, S(E≫mc2)∝E-(k+1). The total annihilation rate and energy losses decrease with decreasing k, being higher than for the isotropic e± power-law distributions at the same k. The radiation is linearly polarized in the plane formed by the magnetic field and wave-vector. The polarization degree P is maximum at E≫mc2:Pmax≃0.6 for θ{symbol}=π/2. Annihilation features and power-law-like hard tails observed in many gamma-ray burst spectra may be associated with the annihilation radiation of the magnetized power-law distributed plasma near neutron stars. Comparison of the observed and theoretical spectra allows one to estimate the power-law index of the e-e+-distribution and the gravitational redshift factor in the radiating region.

Original languageEnglish (US)
Pages (from-to)175-200
Number of pages26
JournalAstrophysics and Space Science
Volume192
Issue number2
DOIs
StatePublished - Jun 1 1992

Fingerprint

electron-positron plasmas
power law
magnetic field
plasma
electron
radiation
magnetic fields
power law distribution
energy
polarization
blue shift
transform
gamma ray bursts
neutron stars
cooling
positrons
energy dissipation
slopes
photons

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

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title = "Annihilation radiation from a power-law distributed electron-positron plasma on the ground Landau level: the case of low magnetic fields",
abstract = "Intensity, polarization, and cooling rate of the two-photon annihilation radiation are studied in detail in the case of one-dimensional power-law distributions of electrons and positrons, assuming that they occupy the ground Landau level in a strong magnetic field B∼1010-1012 G. Simple analytical expressions for limiting cases are obtained and results of numerical calculations of radiation characteristics are presented. Power-law e± distributions η± ∝ ε±-k are shown to generate power-law spectra of the annihilation radiation at E≫mc2 and E≪mc2, with indices depending on the direction of radiation. The annihilation spectra at θ{symbol}=0 show the largest blue-shifts of their maxima and the hardest high-energy tails I(E≫mc2, θ{symbol}=0)∝E-(k-1). The blue-shifts reduce, and the hard tials steepen, with increasing θ{symbol}. At θ{symbol}>(2 mc2/E)1/2 the slopes of the high-energy tails rapidly transform to that at θ{symbol}=π2, I(E≫mc2, θ{symbol}=π/2)∝E-(2 k+3). The direction-integrated spectra S(E) also display the power-law tials at low and high energies, S(E≫mc2)∝E-(k+1). The total annihilation rate and energy losses decrease with decreasing k, being higher than for the isotropic e± power-law distributions at the same k. The radiation is linearly polarized in the plane formed by the magnetic field and wave-vector. The polarization degree P is maximum at E≫mc2:Pmax≃0.6 for θ{symbol}=π/2. Annihilation features and power-law-like hard tails observed in many gamma-ray burst spectra may be associated with the annihilation radiation of the magnetized power-law distributed plasma near neutron stars. Comparison of the observed and theoretical spectra allows one to estimate the power-law index of the e-e+-distribution and the gravitational redshift factor in the radiating region.",
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Annihilation radiation from a power-law distributed electron-positron plasma on the ground Landau level : the case of low magnetic fields. / Kaminker, A. D.; Pavlov, George; Mamradze, P. G.

In: Astrophysics and Space Science, Vol. 192, No. 2, 01.06.1992, p. 175-200.

Research output: Contribution to journalArticle

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