Low Luminosity Stars and White Dwarfs

Abstract

(1) When discussing properties of stars of low luminosity we should first define what we mean by that term. My own feeling is that a bolometric luminosity of 0.001 of that of the Sun appears to be a reasonable upper limit for ‘low luminosity’. Further, it is obvious that, in order to find any numbers of them, one must go down to the very faintest objects, near the limit of what our present telescopes can show. This, in turn, means that virtually no accurate magnitudes, colors, or parallaxes will be available, and that our observational data must be obtained almost exclusively from proper motion surveys for very faint stars. Thus we end up by saying that only the 48-in. Palomar Schmidt telescope can produce large numbers of them. Such a statement is, of course, an oversimplification, but how much of one can be judged from the fact that when three years ago I published a catalogue of 1055 such stars only 36 had come from other sources, and 1019, or 961/2% from the Palomar Schmidt plates. We have now processed more than 400 pairs of plates with our automated-computerized blink machine, and we have at least another 1000 new, low-luminosity stars, and the Palomar Schmidt contribution reaches at least 98%.