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Session 40 - Supernova Remnants & SN 1987A.
Display session, Thursday, January 08
Exhibit Hall,
The fast-moving supernova ejecta drive a blast wave through a moderately dense H\,II region interior to the inner ring of SN\,1987A. The shocked H\,II region is now visible through its X-ray and radio emission. But the circumstellar medium of SN\,1987A, including the H\,II region, contains dust which produced light echoes shortly after the explosion. The dust in the shocked H\,II region is heated by thermal electrons to a temperature of \sim 170 K, and should be a strong emitter of infrared (IR) radiation. The calculated IR spectrum peaks in the wavelength range 10--20 \mum. Assuming a conservative gas/dust mass ratio of 1000, the predicted IR flux density is \sim 10 mJy in this wavelength range. This emission should be detectable with ISOCAM onboard the Infrared Space Observatory (ISO).
The supernova ejecta themselves also produce line and continuum IR radiation. The strongest line is expected to be [\,Fe\,II\,] 26 \mum. The flux in this line is simply related to the energy input by the radioactive decay of ^44Ti, and was expected to be easily detected by ISO. However, an ISO SWS spectrum of the region around 26 \mum does not show any evidence of the line, giving an upper limit on the ^44Ti mass of 1.5 \times 10^-5 M_ødot. This is much lower than the 10^-4 M_ødot usually assumed. The UV and optical emission, produced by the decay of ^44Ti in the Fe-rich core and by recombination in the hydrogen envelope, heats the dust in the SN ejecta. This heated dust emits in the IR, but its detection might be difficult because the dust is cooler and the predicted IR luminosity is an order of magnitude lower than for the collisionally-heated dust in the H\,II region.
