AAS 204th Meeting, June 2004
Session 74 Stellar Leftovers
Poster, Thursday, June 3, 2004, 9:20am-4:00pm, Ballroom

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[74.17] A New Thermal Composite Supernova Remnant, G65.2+5.7

R. L. Shelton (University of Georgia), K. D. Kuntz (University of Maryland at Baltimore County), R. Petre (NASA's GSFC)

G65.2+5.7 has long been known to be a large old supernova remnant. The archival ROSAT PSPC observations presented in this poster reveal that this remnant's interior is X-ray bright, while its shell is X-ray dim. These observations, in combination with existing radio-frequency observations, qualify G65.2+5.7 to be a member of the intriguing "thermal composite" class of SNRs (also known as "mixed morphology" SNRs).

Many hypothesis had been put forth to explain these remnants' odd combination of features (thermal X-ray bright centers, thermal X-ray dim shells, and radio synchrotron shells). One hypothesis explains the lack of X-ray shells by suggesting that these remnants have evolved beyond the adiabatic phase (in which their shockfronts are hot and X-ray emissive), into the radiative phase (in which their shockfronts are cool and X-ray dim). G65.2+5.7, with its optically observed, cool, dense shell, provides crucial support for this hypothesis.

NASA supported this work, through grant number NAG5-10807.

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