Temperatures of Stars in Planetary Nebulæ

Abstract

DURING the past summer, when working at the Dominion Astrophysical Observatory in Victoria, I secured some quantitative data as regards the luminosity of planetary nebulæ. I did not have occasion to elaborate the material until this winter, which I spent in Pasadena, on my leave of absence from the University of Washington at Seattle.¹ The method consists of taking a slitless spectrogram of the nebula with its central star, and impressing on the same film on which this spectrum is taken a series of comparison spectra of varying intensities and of the same time of exposure as the nebula. The comparison spectra are obtained from a sensitometer having the daylight sky as a source, a real image of the sensitometer patches being formed at the slit of the spectrograph. The photographs yield the total intensity of each monochromatic picture of the nebular envelope in terms of the intensity per frequency unit of the adjoining star spectrum of approximately the same wave-length.