Modelling high-energy pulsar light curves from first principles

Current models of gamma-ray light curves in pulsars suffer from large uncertainties on the precise location of particle acceleration and radiation. Here, we present an attempt to alleviate these difficulties by solving for the electromagnetic structure of the oblique magnetosphere, particle accelera...

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Bibliographic Details
Published in:Monthly notices of the Royal Astronomical Society 2016-04, Vol.457 (3), p.2401-2414
Main Authors: Cerutti, Benoît, Philippov, Alexander A., Spitkovsky, Anatoly
Format: Article
Language:English
Subjects:
Astronomy
Astrophysics
Caustics
Current sheets
Cylinders
Emission
Gamma ray astronomy
Gamma rays
Particle acceleration
Pulsars
Radiation
Sciences of the Universe
Star & galaxy formation
Three dimensional
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Summary:Current models of gamma-ray light curves in pulsars suffer from large uncertainties on the precise location of particle acceleration and radiation. Here, we present an attempt to alleviate these difficulties by solving for the electromagnetic structure of the oblique magnetosphere, particle acceleration, and the emission of radiation self-consistently, using 3D spherical particle-in-cell simulations. We find that the low-energy radiation is synchro-curvature radiation from the polar-cap regions within the light cylinder. In contrast, the high-energy emission is synchrotron radiation that originates exclusively from the Y-point and the equatorial current sheet where relativistic magnetic reconnection accelerates particles. In most cases, synthetic high-energy light curves contain two peaks that form when the current sheet sweeps across the observer's line of sight. We find clear evidence of caustics in the emission pattern from the current sheet. High-obliquity solutions can present up to two additional secondary peaks from energetic particles in the wind region accelerated by the reconnection-induced flow near the current sheet. The high-energy radiative efficiency depends sensitively on the viewing angle, and decreases with increasing pulsar inclination. The high-energy emission is concentrated in the equatorial regions where most of the pulsar spin-down is released and dissipated. These results have important implications for the interpretation of gamma-ray pulsar data.
ISSN:0035-8711
1365-2966
DOI:10.1093/mnras/stw124