Comparison of multiwavelength observations of 9 broad-band pulsars with the spectrum of the emission from an extended current with a superluminally rotating distribution pattern

TL;DR

This paper models pulsar spectra across multiple wavelengths using a unified emission process involving an extended superluminally rotating current, successfully explaining diverse spectral features with a single theoretical framework.

Contribution

It introduces a novel model of pulsar emission based on an extended superluminal current, providing a unified explanation for multiwavelength spectra of pulsars.

Findings

Quantitative fit of pulsar spectra with the model

Explanation of ultraviolet and X-ray peaks as oscillatory maxima

Universal spectral steepening linked to observer's Rayleigh distance crossing

Abstract

The observed spectra of 9 pulsars for which multiwavelength data are available from radio to $X$- or $\gamma$-ray bands (Crab, Vela, Geminga, B0656+14, B1055-52, B1509-58, B1706-44, B1929+10, and B1951+32) are compared with the spectrum of the radiation generated by an extended polarization current whose distribution pattern rotates faster than light {\it in vacuo}. It is shown that by inferring the values of two free parameters from observational data (values that are consistent with those of plasma frequency and electron cyclotron frequency in a conventional pulsar magnetosphere), and by adjusting the spectral indices of the power laws describing the source spectrum in various frequency bands, one can account {\em quantitatively} for the entire spectrum of each pulsar in terms of a single emission process. This emission process (a generalization of the synchrotron-\'Cerenkov process to a volume-distributed source in vacuum) gives rise to an oscillatory radiation spectrum. Thus, the bell-shaped peaks of pulsar spectra in the ultraviolet or $X$-ray bands (the features that are normally interpreted as manifestations of thermal radiation) appear in the present model as higher-frequency maxima of the same oscillations that constitute the emission bands observed in the radio spectrum of the Crab pulsar. Likewise, the sudden steepening of the gradient of the spectrum by -1, which occurs around $10^{18}-10^{21}$ Hz, appears as a universal feature of the pulsar emission: a feature that reflects the transit of the position of the observer across the frequency-dependent Rayleigh distance. Inferred values of the free parameters of the present model suggest, moreover, that the lower the rotation frequency of a pulsar, the more weighted towards higher frequencies will be its observed spectral intensity.