A ug 2 00 7 Chandra View of DA 530 : A Sub - energetic Supernova Remnant with a Pulsar Wind Nebula ?

DA 530 (G93.3+6.9) is a high Galactic latitude supernova 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 with 5.3σ above the background within a circle of 20 radius. The spectrum of this feature can be characterized by a power-law with the photon index Γ = 1.6± 0.8. This feature, spatially coinciding 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 interior with a background-subtracted count rate of ∼ 0.06 counts s in 0.3-3.5 keV. The spectrum of the emission can be described by a thermal plasma with a temperature of ∼ 0.3–0.6 keV and a Si over-abundance of & 7 solar. These spectral characteristics, together with the extremely low X-ray luminosity, suggest that the remnant arises from a supernova with an anomalously low mechanical energy (< 10 ergs). The centrally-filled thermal X-ray emission of the remnant may indicate an early thermalization of the SN ejecta by the circum-stellar medium. Our results suggest that the remnant is likely the product of a core-collapsed SN with a progenitor mass of 8-12 M⊙. Similar remnants are probably common in the Galaxy, but have rarely been studied. Subject headings: supernova remnants: individual: DA 530 (G93.3+6.9) — X-rays: ISM