Abstract
Otto Struve and P. Swings have an article with this title in the August issue of the Observatory (No. 809, 64, August, 1942). Morgan pointed out about seven years ago that there is some physical factor other than temperature and surface gravity concerned in the production of the spectra of these stars. The theory of ionization has failed to solve the problem, and the authors are convinced that existing interpretations, which are very unsatisfactory, should be abandoned. They believe that a new solution should be attempted along lines which have been forced on them by the results of their recent work on stellar shells, Wolf-Rayet stars and planetary nebulae. It is suggestive that certain peculiarities occur in that region of the sequence of the stellar spectra where the Lyman lines and the Lyman continuous absorption cause a large redistribution of the energy in the continuous spectrum. This redistribution has a profound effect on the continuous spectrum of an A star, as shown by the curve computed by Panne-koek for a temperature To = 8,480°, and it must have a marked instances of this are given. A wide variety of unexplained observations are capable of interpretation along the general lines suggested by the authors, details of which are to be published in the Astro -physical Journal. Departures from thermodynamic equilibrium are now being emphasized by recent developments in stellar spectroscopy, in contrast to the long and successful period characterized by the use of thermodynamic equilibrium.
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The Problems of the A-Type Stars. Nature 150, 370–371 (1942). https://doi.org/10.1038/150370d0
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DOI: https://doi.org/10.1038/150370d0