FOSSIL SYMBIOTIC NOVAE

While a symbiotic nova's outburst quickly degrades the molecular conte nt of a circumstellar shell, it takes almost-equal-to 1000 yr to move fresh material out from a star to its OH masing zone. During this post -outburst phase a shell lacks its usual complement of molecules, and s o bears a stamp from the nova outburst, even though it is no longer a soft X-ray, UV or radio source. These objects are ''fossil'' symbiotic novae. The number of potential ''fossils'' with dense shells is comme nsurate with the frequency of observed Galactic symbiotic novae. The d ensest O-rich shells exhibit the 9.7 mum silicate line in absorption. This places them in the IRAS low resolution spectral type 38-39 class. About 50% of these mass-losing giants have had comparably massive com panions. Of 38 class members examined at 1612 MHz, 32 exhibit masers. But six (16%) lack them. We identify these six with ''fossil'' symbiot ic novae.