The Chandra View of DA 530: A Subenergetic Supernova Remnant with a Pulsar Wind Nebula?

DA 530 (G93.3+6.9) is a high Galactic latitude supernova (SN) remnant with a well-defined shell-like radio morphology and an exceptionally low X-ray-to-radio luminosity ratio. Based on a Chandra ACIS observation, we report the detection of an extended X-ray feature close to the center of the remnant at 5.3 σ above the background within a circle of 20'' radius. The spectrum of this feature can be characterized by a power law with photon index Γ = 1.6 ± 0.8. This feature, which is spatially coincident with a nonthermal radio source, most likely represents a pulsar wind nebula. We have further examined the spectrum of the diffuse X-ray emission from the remnant's interior, which has a background-subtracted count rate of ~0.06 s^-1 at 0.3-3.5 keV. The emission spectrum can be described by a thermal plasma with a temperature of ~0.3-0.6 keV and an Si overabundance of ≳7 times solar. These spectral characteristics, together with the extremely low X-ray luminosity, suggest that the remnant arose from a SN with an anomalously low mechanical energy (<10⁵⁰ ergs). The centrally filled thermal X-ray emission of the remnant may indicate an early thermalization of the SN ejecta by the circumstellar medium. Our results suggest that the remnant is likely the product of a core-collapse SN with a progenitor mass of 8-12 M_☉. Similar remnants are probably common in the Galaxy but have rarely been studied.