Baschek, B. | Search NASA

NASA NTRS1988

The chemical composition of the Lambda Bootis stars

Measurements of the equivalent widths of 24 ultraviolet lines from IUE spectra of 10 Lambda Bootis or suspected Lambda Bootis stars and 19 normal standard stars of spectral types B8-A7 have been compared with line strengths determined using model atmospheres. Abundance differences are estimated via a differential analysis technique. It is found that the ratio of C, N, and O to the heavier elements Mg to Ni is significantly larger than that for solar composition stars.

Baschek, B.↗

NASA NTRS1988

The analysis of spectra of novae taken near maximum

A project to analyze ultraviolet spectra of novae obtained at or near maximum optical light is presented. These spectra are characterized by a relatively cool continuum with superimposed permitted emission lines from ions such as Fe II, Mg II, and Si II. Spectra obtained late in the outburst show only emission lines from highly ionized species and in many cases these are forbidden lines. The ultraviolet data will be used with calculations of spherical, expanding, stellar atmospheres for novae to determine elemental abundances by spectral line synthesis. This method is extremely sensitive to the abundances and completely independent of the nebular analyses usually used to obtain novae abundances.

Stryker, L. L.↗