R. P. Kirshner

Ionization Structure of the Cygnus Loop

A survey instrument capable of narrow band filter imagery has been put into operation at KPNO. It consists of large diameter filters with 27 to 90 Angstroms (full width at half transmission), a commercially available 300 mm f/2.8 lens and a two-stage magnetically focused image intensifier. Frames having thirty arcsecond angular resolution over a nominal seven degree field of view are recorded to sky background limit in ten to fifteen minutes. This camera is being used to survey the galactic plane in Hβ,[SII] (6725 A), [OIII] (5007 A), Hα + [NII] (6570 A) and continuum at 4770 A. A preliminary program surveying special objects such as supernova remnants is near completion.

ABUNDANCES IN SUPERNOVAE

The temperature and density in the expanding envelope of a supernova can be derived from spectrophotometry. Once the physical conditions are known, the observed line strengths of emission and absorption features can be used to estimate the abundances of elements in the ejected material. For SN IIs, a consistent model that explains the presence, strengths, and evolution of many spectral features requires about 3 M/sub solar/ of hydrogen in the ejecta and solar abundances of iron, oxygen, magnesium, sodium, and calcium. For SN Is, no such definite model is suggested, but one possibility that accounts for some of the strong emission features observed many months after maximum light is that the ejecta include roughly 1 M/sub solar/ of hydrogen and about 10/sup -2/ M/sub solar/ of once ionized iron. This value is 20 times the mass of iron in the Sun and raises the perennial suggestion that supernovae may have some connection with the formation of elements. 7 references. (BJG)