A classification atlas of stellar spectra of luminosity types III and V for the Burke-Gaffney Observatory

Abstract

The MK classification system is defined by the spectra of an array of standard stars and is based on the appearances and relative intensities of selected spectral lines, blends, and bands observed in the blue-violet region of the spectrum. In spite of recent studies showing the necessity of revising the system to include an abundance parameter, the MK system remains a two dimensional classification system based on temperature types and luminosity classes. A Spotz spectrograph which was recently acquired by the Burke-Gaffney Observatory, was used after an initial period of testing, to produce a series of spectrograms of selected MK standard stars of luminosity types III and V. The testing period was necessary to obtain the correct spectrograph operating settings (camera focus, grating title, slit width, and stellar exposure times) and to devise a satisfactory observing procedure for photographing stellar spectra in the blue-violet wavelength region. The resulting photographic sequence or atlas of spectrograms could then be used at the Burke-Gaffney Observatory to assign MK classifications to other stars. Eleven program stars were employed to test the classification capability and accuracy of the produced atlas. The results proved very satisfactory as in all cases the atlas-assigned spectral types were within one subclass of the accepted classifications and nine of the eleven stars were given the correct luminosity classes. Secondary objectives involved the testing of the classification capacity of the spectrograph when using the Observatory’s Varo image tube and a study of the Halifax night sky spectrum. The results of the image tube testing indicated that a classification atlas using this apparatus may prove valuable and should be produced. The night sky spectrum of Halifax was heavily marked with emission lines from mercury and sodium vapour lamps.