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Spectral Hardening in the Trailing Peak of Gamma-ray Pulsar Light Curve

圖片來源: Kouichi Hirotani

Evolution of the photon index Γ (top panel) and the cutoff energy Ec (bottom panel) with the rotational phase is depicted by the (red) thick solid curve.

So far, the six brightest gamma-ray pulsars, which allow us to measure their detailed phase-resolved spectra, all show a spectral hardening in the second light-curve peak in GeV energies. Specifically, they show an increase of the "cutoff energy" of a power-law spectral shape in the second peak. Considering the actual particle motion in the three-dimensional pulsar magnetosphere, this work first explained this general behavior of spectral hardening, as indicated by the lower panel. (Kouichi Hirotani, Astrophys. J. 733, Letters 49-53 (2011))