Slow diffusion is necessary to explain the gamma-ray pulsar halos

Abstract

It was suggested that the $\gamma$-ray halo around Geminga might not be interpreted by slow-diffusion. If the ballistic regime of electron/positron propagation is considered, the Geminga halo may be explained even with a large diffusion coefficient. In this work, we examine this effect by taking the generalized Jüttner propagator as the approximate relativistic Green's function for diffusion and find that the morphology of the Geminga halo can be marginally fitted in the fast-diffusion scenario. However, the recently discovered $\gamma$-ray halo around PSR J0622$+$3749 at LHAASO cannot be explained by the same effect and slow diffusion is the only solution. Furthermore, both the two pulsar halos require a conversion efficiency from the pulsar spin-down energy to the high energy electrons/positrons much larger than 100\%, if they are interpreted by this ballistic transport effect. Therefore, we conclude that slow diffusion is necessary to account for the $\gamma$-ray halos around pulsars.

11 pages, 8 figures; version accepted by APJ

References in corpus (7)

• Extended gamma-ray sources around pulsars constrain the origin of the positron flux at Earth
• Extended Very-High-Energy Gamma-Ray Emission Surrounding PSR J0622 + 3749 Observed by LHAASO-KM2A
• Relativistic diffusion processes and random walk models
• Does the Geminga, Monogem and PSR J0622+3749 $\gamma$-ray halos imply slow diffusion around pulsars?
• Relative entropy, Haar measures and relativistic canonical velocity distributions
• Klein-Nishina effect and the cosmic ray electron spectrum
• Self-consistent interpretations of the multi-wavelength gamma-ray spectrum of LHAASO J0621$+$3755

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• Features of the gamma-ray pulsar halo HESS J1831$-$098
• Effect of magnetic field correlation length on the gamma-ray pulsar halo morphology under anisotropic diffusion
• Constraining the slow-diffusion zone size and electron injection spectral index for the Geminga pulsar halo
• Constraints on the $e^{\pm }$ Pair Injection of Pulsar Halos: Implications from the Galactic Diffuse Multi-TeV Gamma-ray Emission
• A rigorous solution to the superluminal issue in the diffusion equation
• PHECT: A lightweight computation tool for pulsar halo emission
• Anisotropic Diffusion in Pulsar Halos: Interpreting the asymmetric morphology of Geminga and Monogem halos measured by HAWC
• Suppressed diffusion and gamma-ray emission from the Cygnus bubble