Simultaneous Photometric and Image-Tube Spectroscopic Observations of Short Period Binary Systems and Rapid Intrinsic Variables

Abstract

An extremely important new frontier in variable star research lies in the application of image tube techniques to the study of the spectroscopic phenomena in extremely rapid intrinsic variables and in short-period binary systems. Within limits, the use of image tubes for the spectroscopic observation of constant or slowly varying stars can be regarded as a convenience — as a means of increasing the efficiency of use of time at the telescope; the same results could, in principle, be obtained by observing for a longer time by conventional means. However, when one wishes to observe rapid changes, there is no substitute for the higher information collection rate provided by the image tube. Electronographic image tubes are especially well suited to this type of investigation owing to their high quantum efficiency, high resolution, large storage capacity, and linearity of response. Typically, image tubes of this type may have quantum efficiencies of 10% to 20%, an information-rate gain of 10 to 20 over the fastest photographic plate (baked Kodak IIaO at 4000 A), and resolutions between 80 and 100 lp/mm. With proper choice of photographic emulsion to record the electronic images, a linear relationship exists between photographic density and intensity of the incident light up to densities of about six, making electronographic image tubes especially valuable for spectrophotometric observations. Despite the great potential of this technique, very little work of this type has so far been done. In this paper I shall outline some of the results that have been obtained at Mount Hamilton to illustrate the possibilities of this type of observational research.