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Energy-dependent extension of the Crab Nebula as a diagnostic of ultrahigh-energy hadronic emission

Fang-Wu Lu1, Bo-Tao Zhu2,*, Ji-Yang Ren1, and Li Zhang3,†

  • *Contact author: bo_taozhu@126.com
  • †Contact author: lizhang@ynu.edu.cn
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Phys. Rev. D 114, 043066 – Published 25 August, 2026

DOI: https://doi.org/10.1103/dnsv-plc9

Abstract

The energy-dependent apparent extension of the Crab Nebula, inconsistent with leptonic expectations between x-ray and TeV bands, can be naturally accounted for in a spatially resolved lepto-hadronic scenario. A transition to hadronic dominance occurs above ∼400  TeV, with nearly pure hadronic emission at PeV energies. The predicted 68% containment radius at 1.1 PeV is ∼1.4′, about six times larger than in purely leptonic scenarios. This energy-dependent extension therefore provides an observable discriminator of the origin of ultrahigh-energy gamma-ray emission in pulsar wind nebulae, offering a diagnostic of PeV hadronic acceleration in the Crab Nebula.

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Phys. Rev. D 114, 043066– Published 25 August, 2026
  • Received 15 April 2026
  • Accepted 27 July 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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