Temporal and Spatial Variation of Synchrotron X-ray Stripes in Tycho's Supernova Remnant

TL;DR

This study investigates the temporal and spatial variability of synchrotron X-ray stripes in Tycho's supernova remnant, revealing frequent variability, spectral hardness differences, and implications for magnetic field amplification and stochastic particle acceleration.

Contribution

It provides the first detailed analysis of the variability and spectral properties of multiple X-ray stripes over time, suggesting magnetic field amplification and stochastic acceleration processes.

Findings

Time variability is more common among stripes than previously reported.

A strong anti-correlation exists between surface brightness and photon indices.

Stripes exhibit harder spectra than the outer rim, indicating magnetic field amplification.

Abstract

The synchrotron X-ray "stripes" discovered in Tycho's supernova remnant (SNR) have been attracting attention since they may be evidence for proton acceleration up to PeV. We analyzed Chandra data taken in 2003, 2007, 2009, and 2015 for imaging and spectroscopy of the stripes in the southwestern region of the SNR. Comparing images obtained at different epochs, we find that time variability of synchrotron X-rays is not limited to two structures previously reported but is more common in the region. Spectral analysis of nine bright stripes reveals not only their time variabilities but also a strong anti-correlation between the surface brightness and photon indices. The spectra of the nine stripes have photon indices of \Gamma = 2.1--2.6 and are significantly harder than those of the outer rim of the SNR in the same region with \Gamma = 2.7--2.9. Based on these findings, we indicate that the magnetic field is substantially amplified, and suggest that particle acceleration through a stochastic process may be at work in the stripes.