G64.5+0.9, a new shell supernova remnant with unusual central emission

TL;DR

This paper confirms G64.5+0.9 as a new Galactic shell supernova remnant with an unusual central emission, using multi-frequency radio observations, and discusses its spectral properties and possible nature.

Contribution

The study provides detailed spectral analysis of G64.5+0.9, identifying a shell structure and unusual central emission, and rules out extragalactic origins, contributing new insights into this remnant's characteristics.

Findings

G64.5+0.9 is a shell supernova remnant approximately 8 arcmin in diameter.

The remnant's spectral index is approximately 0.47, with central emission having a spectral index of about 0.81.

No spectral breaks were observed within the 1.4 to 18 GHz frequency range.

Abstract

We present observations between 1.4 and 18 GHz confirming that G64.5+0.9 is new Galactic shell supernova remnant, using the Very Large Array and the Arcminute Microkelvin Imager. The remnant is a shell ~8 arcmin in diameter with a spectral index of alpha = 0.47 +/- 0.03 (with alpha defined such that flux density S varies with frequency nu as S proportional to nu to the power of -alpha). There is also emission near the centre of the shell, ~1 arcmin in extent, with a spectral index of alpha = 0.81 +/- 0.02. We do not find any evidence for spectral breaks for either source within our frequency range. The nature of the central object is unclear and requires further investigation, but we argue that is most unlikely to be extragalactic. It is difficult to avoid the conclusion that it is associated with the shell, although its spectrum is very unlike that of known pulsar wind nebulae.