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[10.18] The Central Engine of the Unusual Supernova Remnant DA 495

Z. Arzoumanian (USRA/NASA-GSFC), S. Safi-Harb (Univ. of Manitoba), R. Kothes, T. Landecker (DRAO, NRC-Canada)

We describe new and archival X-ray observations of the synchrotron nebula DA 495 (G65.7+1.2), a likely supernova remnant with properties similar to those of the Crab Nebula. Two unusual features of the radio nebula are its uncharacteristically steep radio spectrum and its annular morphology, with a flux minimum at the geometrical center. A recently acquired Chandra image confirms results derived from earlier ROSAT and ASCA observations: the X-ray morphology strongly suggests extended ``plerionic'' emission roughly centered on a hard, unresolved source lying near the edge of the central radio ``hole.'' The power-law spectrum of the source is consistent with that of a magnetospherically active neutron star. Our results reveal for the first time the high-energy engine powering the synchrotron nebula, and strengthen the classification of DA 495 as a plerionic supernova remnant, one that may represent a late evolutionary stage of Crab-like plerions.

Bulletin of the American Astronomical Society, 35#2
© 2003. The American Astronomical Soceity.