The quantitative chemical analysis of early-type stars

Abstract

The University of Michigan programme for the determination of the abundances of the elements in hot stars involves an observational, a theoretical, and an experimental phase. A description of the spectrum of [gamma] Pegasi from [lambda]3570-[lambda]3970 and the profiles of the stronger linesin the photographic region illustrate the type of observational material that is being employed in this investigation. The point of view adopted for the theoretical programme is next described. Briefly, the model atmosphere of any given star must represent the observations of the continuous energy distribution, the Balmer discontinuity, the relative intensities of different spectral lines and the profiles of the stronger lines, notably those of hydrogen and helium. For this phase, a knowledge of the line-broadening coefficient is essential. Hence the emphasis on the experimental work with the luminous shock tube in which the Stark broadening of lines of hydrogen and other gases can be studied.