Reconstructing the Guitar: Blowing Bubbles with a Pulsar Bow Shock Back Flow

TL;DR

This paper proposes that the unique morphology of the Guitar Nebula results from instabilities in the back flow of the pulsar's bow shock, with simulations showing how these lead to bubble formation consistent with observations.

Contribution

It introduces a novel scenario linking back flow instabilities to the formation of nebula bubbles, supported by simulations matching observed features.

Findings

Back flow instabilities can produce bubble structures.

Simulated bubble sizes and velocities match observations.

Instabilities may explain features in other bow shocks.

Abstract

The Guitar Nebula is an H-alpha nebula produced by the interaction of the relativistic wind of a very fast pulsar, PSR B2224+65, with the interstellar medium. It consists of a ram-pressure confined bow shock near its head and a series of semi-circular bubbles further behind, the two largest of which form the body of the Guitar. We present a scenario in which this peculiar morphology is due to instabilities in the back flow from the pulsar bow shock. From simulations, these back flows appear similar to jets and their kinetic energy is a large fraction of the total energy in the pulsar's relativistic wind. We suggest that, like jets, these flows become unstable some distance down-stream, leading to rapid dissipation of the kinetic energy into heat, and the formation of an expanding bubble. We show that in this scenario the sizes, velocities, and surface brightnesses of the bubbles depend mostly on observables, and that they match roughly what is seen for the Guitar. Similar instabilities may account for features seen in other bow shocks.