An XMM–Newton study of Kesteven 69: Challenging the classification as a typical thermal composite supernova remnant?

Abstract Supernova remnants are diffuse nebulae generated by the interaction of supernova explosions with the surrounding environment, usually observed in the X-ray band. Thermal composite supernova remnants are primarily characterized by their center-brightened emission, yet they lack an associated pulsar wind nebula. Within this category, Kesteven 69 has traditionally been the sole candidate without gamma-ray detection or recombining plasma emission. In this study, the first Australian Square Kilometre Array Pathfinder image and the XMM–Newton background-subtracted image are presented, and spatially resolved spectral analyses are described. These multiwavelength investigations reveal a novel perspective that Kesteven 69 is likely to be a shell-type supernova remnant located on the periphery of molecular clouds, featuring two major X-ray arcs. This finding suggests a reevaluation of the unusual morphology observed in other special thermal composite supernova remnant candidates.