An assessment of the pulsar outer gap model. I: Assumptions, uncertainties, and implications for the gap size and the accelerating field

Abstract

The popular outer gap model of magnetospheric emission from pulsars has been widely applied to explain the properties observed in $\gamma$-rays. However, its quantitative predictions rely on a number of approximations and assumptions that are usually overlooked. Here we examine them, reviewing the main ingredients entering in the model, evaluating their range of uncertainties. Usually, in the quantitative applications of the model, key parameters like the radius of curvature and the energies of the interacting photons are taken to be a fixed, single value. Instead, here we explore their realistic ranges, and the impact of these on the consistency of the model itself. We conclude that the popular evaluation of the trans-field size of the gap as a function of period and period derivative, is unreliable and affected by a huge dispersion. Last, the exploration of the possible values for the radius of curvature, the local magnetic field and other quantities deserve more attention for quantitative applications of the outer gap model, like the calculation of $\gamma$-ray spectra, which is the subject of an accompanying paper.

arXiv comment19 pages, 5 figures, 3 tables. Accepted for pubblication in MNRAS main journal. References updated

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• Modeling of the gamma-ray pulsed spectra of Geminga, Crab, and Vela with synchro-curvature radiation
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• An assessment of the pulsar outer gap model. II: Implications for the predicted $\gamma$-ray spectra
• Very High-Energy Emission from the Direct Vicinity of Rapidly Rotating Black Holes
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• Efficiency of Synchrotron Radiation from Rotation-Powered Pulsars
• A novel approach for the analysis of the geometry involved in determining light curves of pulsars
• Dissecting the emission from LHAASO J0341+5258: implications for future multi-wavelength observations
• Strongly pulsed thermal X-rays from a single extended hot spot on PSR J2021+4026
• Energy release from magnetospheres deformed by gravitational waves
• Detection of the Geminga pulsar at energies down to 20 GeV with the LST-1 of CTAO
• The Potential for Hadronic Particle Acceleration in Galactic Pulsar Wind Nebulae
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