Rapid X-ray variations of the Geminga pulsar wind nebula

TL;DR

This study reports rapid X-ray variability in the Geminga pulsar wind nebula, including morphological changes, a bent jet possibly caused by torsional Alfven waves, and spectral hardening, revealing dynamic processes in the nebula.

Contribution

It provides the first detailed observation of rapid morphological and spectral variations in the Geminga PWN, highlighting dynamic behaviors on timescales of days to months.

Findings

Detected variability in nebula components over days to months

Observed jet bending and wiggling at significant fractions of light speed

Identified spectral hardening along the tail for about nine months

Abstract

A recent study by Posselt et al. (2017) reported the deepest X-ray investigation of the Geminga pulsar wind nebula (PWN) by using \emph{Chandra X-ray Observatory}. In comparison with previous studies of this system, a number of new findings have been reported and we found these suggest the possible variabilities in various components of this PWN. This motivates us to carry out a dedicated search for the morphological and spectral variations of this complex nebula. We have discovered variabilities on timescales from a few days to a few months from different components of the nebula. The fastest change occurred in the circumstellar environment at a rate of 80 per cent of the speed of light. One of the most spectacular results is the wiggling of a half light-year long tail as an extension of the jet, which is significantly bent by the ram pressure. The jet wiggling occurred at a rate of about 20 per cent of the speed of light. This twisted structure can possibly be a result of a propagating torsional Alf\`{v}en wave. We have also found evidence of spectral hardening along this tail for a period of about nine months.