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arXiv · 2607.29126

Polar cap plasma loading and the morphology of pulsar $γ$-ray light curves

Jérôme Pétri
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Abstract

The discovery of more than 300 $γ$-ray pulsars by the Fermi Large Area Telescope (Fermi-LAT) has revealed a rich diversity of light-curve morphologies that remains challenging to reproduce within purely magnetospheric emission models, suggesting that particle acceleration and radiation may occur, at least in part, in the striped-wind current sheet. We compute a comprehensive atlas of pulsar $γ$-ray light curves based on the split-monopole current sheet geometry, with the goal of quantifying the role of pair plasma loading in shaping the observed pulse morphology. The current-sheet surface is described analytically and assumed to be the dominant site of high-energy photon emission. Spatially dependent emissivity prescriptions are introduced through a minimal set of parameters that explicitly break the north-south and azimuthal symmetries of the emitting plasma. With only a few physically motivated parameters, the model is able to reproduce a broad range of the observed $γ$-ray light-curve morphologies, including asymmetric, multi-peaked, and highly structured profiles. The results show that asymmetric emissivity, possibly related to pair-plasma loading, provides a natural and economical mechanism capable of reproducing a substantial fraction of the observed diversity of $γ$-ray pulse profiles. The current-sheet scenario therefore appears to provide a promising and physically motivated framework for high-energy pulsar emission.

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Jérôme Pétri. 2026-07-31. Polar cap plasma loading and the morphology of pulsar $γ$-ray light curves. https://arxiv.org/abs/2607.29126

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