Astronomy and Astrophysics – Astronomy
Scientific paper
Sep 1997
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997mnras.290...49m&link_type=abstract
Monthly Notices of the Royal Astronomical Society, Volume 290, Issue 1, pp. 49-58.
Astronomy and Astrophysics
Astronomy
11
Pulsars: General, Pulsars: Individual: Crab, Gamma-Rays: Theory
Scientific paper
We calculate phase-dependent gamma-ray spectra and energy-dependent pulse shape for the Crab pulsar based on the single polar-cap model and compare our results with the observation obtained by EGRET on the Compton Gamma-ray Observatory (CGRO) satellite. We assume that the acceleration region lies above the surface of the neutron star and that primary electrons are injected at an energy of a few tens of TeV. Injected electrons generate cascade processes of curvature radiation, magnetic pair creation and synchrotron radiation. We investigate the magnetic pair creation more carefully than in previous work and obtain a new approximation formula for the attenuation coefficient applicable to a wider range. We calculate the gamma-ray spectra for three models in which the height of the acceleration region from the surface of the neutron star is taken to be 0, 10^6 and 4x10^6 cm. We find that the phase-averaged spectrum, energy-dependent pulse shape and phase-dependent spectra are basically reproduced when the height is about 10^6cm. However, there remain some detailed discrepancies between our results and observations. We estimate the injection rate of particles to the Crab nebula by multiplying the injection rate of primary electrons with the multiplication factor obtained from cascade processes. It turns out to be 2.6x10^37 s^-1 for the height of 10^6 cm, which is marginally consistent with the estimate based on the X-ray emission of the Crab nebula.
Miyazaki Junichi
Takahara Fumio
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