Spectral Hardening in the Trailing Peak of Gamma-ray Pulsar Light Curve
Figure 5 of "Pulsar Outer-gap Electrodynamics: Hardening of Spectral Shape in the Trailing Peak in Gamma-ray Light Curve", Kouichi Hirotani, Astrophys. J. 733, Letters 49-53 (2011).
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.