Production of pulsed emission from the Crab and Vela pulsars by the synchrotron mechanism

Journal Article · Thu Feb 01 04:00:00 EST 1979 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/156805· OSTI ID:6272293

Hardee, P E

In this paper we show that the pulsed optical, X-ray and ..gamma..-ray emission from the Crab pulsar can be produced by synchrotron emission. The emission region is located at a distance approx.10/sup 8/ cm from the stellar surface where the plasma becomes unstable to filamentation. Self-pinched filaments generate magnetic fields, deltaB, perpendicular to the ambient magnetic field, B, which leads to the scattering of particles entering the unstable region into pitch angles psi<0.01approx.deltaB/B. The average spectrum of emission, assumed continuous from the infrared through ..gamma..-rays, can be generated by a power law distribution of particles with a single power law index approx.2.2 and a low-energy cutoff or turnover E/sub 0/approx. =150mc/sup 2/. Particles with energy E>E/sub 1/2/approx.9 x 10/sup 3/mc/sup 2/ have half-lives tau/sub 1/2/<10/sup -3/ s, and this results in the steepening of the spectral index for frequencies ..nu..>2.5 x 10/sup 18/ Hz. The assumption of a quasi-neutral electron-positron plasma guarantees linearly polarized emission with polarization proportional to the projection of the magnetic field perpendicular to the line of sight. Plausible evolution of this emission mechanism suggests a decrease in the optical and ..gamma..-ray luminosity at least as rapidly as P/sup -9/ and P/sup -4/ (Pequivalent pulsed period), respectively. If radio emission is produced between the surface and the region unstable to filamentation and if ..gamma..-rays can escape from the surface of the Vela pulsar but not the Crab pulsar, it is possible to explain the relative phasing of emission produced by these two pulsars as evolution of three separate emission mechanisms. The angular structure of the Crab's optical pulse profile can be attributed to small angular size in the emission region and aberration. The small angular size can be produced by surface fields approx.10/sup 14/ gauss in high multipole moments.

• Research Organization: National Radio Astronomy Observatory, Charlottesville
• OSTI ID: 6272293
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 227:3; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics &amp; Cosmology-- Stars &amp; Quasi-Stellar
Radio &amp; X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATMOSPHERES
BREMSSTRAHLUNG
COSMIC RADIO SOURCES
ELECTROMAGNETIC RADIATION
EMISSION SPECTRA
FLUID MECHANICS
HYDRODYNAMICS
INSTABILITY
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
MATHEMATICAL MODELS
MECHANICS
PLASMA
PULSARS
PULSATIONS
RADIATIONS
SPECTRA
STAR MODELS
STELLAR ATMOSPHERES
STELLAR MAGNETOSPHERES
STELLAR RADIATION
SYNCHROTRON RADIATION