2004ApJ...615..275S

This paper presents archival ROSAT PSPC observations of the G65.2+5.7 supernova remnant (also known as G65.3+5.7). Little material obscures this remnant, and so it was well observed, even at the softest end of ROSAT's bandpass (∼0.11-0.28 keV). These soft X-ray images reveal the remnant's centrally filled morphology, which, in combination with existing radio frequency observations, places G65.2+5.7 in the thermal composite (mixed-morphology) class of supernova remnants. Not only might G65.2+5.7 be the oldest known thermal composite supernova remnant, but owing to its optically revealed cool, dense shell, this remnant supports the proposal that thermal composite supernova remnants lack X-ray-bright shells because they have evolved beyond the adiabatic phase. These observations also reveal a slightly extended point source centered on R.A. 19^h36^m46^s, decl. 30°40'07" and extending 6'.5 in radius in the band 67 map. The source of this emission has yet to be discovered, as there is no known pulsar at this location.