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

Abstract

We present observations between 1.4 and 18 GHz con?rming that G64.5+0.9 is a new Galacticshell 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 a = 0.47 ± 0.03 (witha de?ned such that ?ux density S varies with frequency ? as S ? ?-a). There is also emissionnear the centre of the shell,1 arcmin in extent, with a spectral index of a =0.81±0.02. Wedo not ?nd any evidence for spectral breaks for either source within our frequency range. Thenature of the central object is unclear and requires further investigation, but we argue that itis most unlikely to be extragalactic. It is dif?cult to avoid the conclusion that it is associatedwith the shell, although its spectrum is very unlike that of known pulsar wind nebulae.