Steady X-Ray Synchrotron Emission in the Northeastern Limb of SN 1006

TL;DR

This study analyzes X-ray synchrotron emission in SN 1006's northeastern limb over eight years, finding minimal flux variation and a correlation between flux and cutoff frequency, suggesting stable magnetic fields and electron acceleration conditions.

Contribution

It provides the first detailed temporal and spatial analysis of synchrotron emission in SN 1006, revealing minimal variability and a flux-cutoff frequency correlation, contrasting with other remnants.

Findings

No significant flux variability detected over 8 years.

Flux decline is likely a calibration artifact, not intrinsic.

Spatial correlation suggests magnetic field influences cutoff frequency.

Abstract

We investigate time variations and detailed spatial structures of X-ray synchrotron emission in the northeastern limb of SN 1006, using two Chandra observations taken in 2000 and 2008. We extract spectra from a number of small (about 10") regions. After taking account of proper motion and isolating the synchrotron from the thermal emission, we study time variations in the synchrotron emission in the small regions. We find that there are no regions showing strong flux variations. Our analysis shows an apparent flux decline in the overall synchrotron flux of about 4% at high energies, but we suspect that this is mostly a calibration effect, and that flux is actually constant to about 1%. This is much less than the variation found in other remnants where it was used to infer magnetic-field strengths up to 1 mG. We attribute the lack of variability to the smoothness of the synchrotron morphology, in contrast to the small-scale knots found to be variable in other remnants. The smoothness is to be expected for a Type Ia remnant encountering uniform material. Finally we find a spatial correlation between the flux and the cut-off frequency in synchrotron emission. The simplest interpretation is that the cut-off frequency depends on the magnetic-field strength. This would require that the maximum energy of accelerated electrons is not limited by synchrotron losses, but by some other effect. Alternatively, the rate of particle injection and acceleration may vary due to some effect not yet accounted for, such as a dependence on shock obliquity.