A unified model for the time variability of the Crab: the dispersion measure variation and the $\gamma$-ray flare of the nebula

TL;DR

This paper proposes a unified model linking dispersion measure variations and gamma-ray flares in the Crab nebula, explaining their correlation through electron activity in the nebula's inner shock region.

Contribution

It introduces a novel model connecting DM fluctuations and gamma-ray flares based on electron dynamics, motivated by observed correlations with the braking index.

Findings

The model explains both DM enhancements and gamma-ray flares simultaneously.

It suggests electrons in the inner shock region drive the observed variability.

The approach provides a unified explanation for different observed phenomena.

Abstract

The Crab pulsar and its nebula are very luminous and variable. Since 1982, random fluctuations of the dispersion measure (DM) have been recorded. Also in 2011, Fermi-LAT telescope detected $\gamma$-ray flux variation of the Crab nebula. No correlation between these phenomena have considered although their fluctuating patterns look similar. We propose a model which connects the DM and the Crab nebula $\gamma$-ray flux fluctuation, motivated by recently reported correlation between the braking index and the DM variability. Considering electrons within the inner shock region of the nebula produced in breaking index change events, we can explain both the DM enhancement and the $\gamma$-ray flare in a simple way.