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Session 53 - SNs, Planetaries and Circumstellar Disks.
Display session, Wednesday, June 10
Atlas Ballroom,

[53.18] The X-ray Properties of SNRs in Diffuse Media

R. L. Shelton (NASA/Goddard Space Flight Center)

Supernova explosions in very tenuous medium are important in many contexts such as the lower Galactic halo, the Local Bubble, and external galaxies. This poster presents the X-ray properties of a simulated supernova remnant (SNR) evolving in a diffuse medium and applies the results to SNRs in the lower Galactic halo.

I present very high resolution spectra, diagrams of the spatial appearance, and estimates for the ROSAT PSPC count rates at various ages in the remnant's life. The X-ray emitting gas is out of collisional equilibrium --- in the young remnant, the gas is dramatically underionized and later it is noticeably overionized. As a result, the remnant has a ROSAT PSPC R1/R2 color temperature of \sim10^6 K during its X-ray bright phase and a slightly lower color temperature thereafter.

Given the progenitor statistics and the duration of the X-ray bright phase in the SNR's evolution, the lower halo in each Galactic hemisphere should contain approximately 1 X-ray bright SNR at any given time. X-ray bright SNRs should cover roughly 1% of the halo and provide hundreds to thousands of ROSAT 1/4 KeV counts s^-1 arcmin^-2. Maps of the halo emission in the south show a couple of bright patches and a dimmer, mottly background. The halo SNRs have the potential to explain a couple of the bright patches seen in the south, while other mechanisms are required to explain the additional more widespread but dimmer emission.

Program listing for Wednesday