The authors compiled this moderate-resolution spectral atlas to aid in the classification of carbon stars on the Revised MK System (Keenan 1993PASP..105..905K) as refined and extended by the present work. Hence the main purpose of this atlas is to permit rapid and reasonably accurate comparison of the properties of carbon stars in the Solar neighborhood with those in the Galactic bulge, the Magellanic Clouds, and in other nearby external systems. The classification scheme employed makes no assumptions about evolutionary status of the stars but is based entirely on observable criteria. Spectra of 39 stars are presented in detail, along with a catalog of 119 carbon stars classified according to the Revised MK System; the catalog lists also the variability type from Kholopov (1985), and the instrument used. The table is a modified version of table 4 in the source reference. This classification catalog uses not only the stars we observed (the spectral data in this catalog) but also used other material -- photographic plates and some of the stars in the high resolution barnbaum atlas. Stars observed solely with those two instruments are so noted. The spectral files are the data for the standard Carbon Stars in Figs 1 and 2 of the paper. Introduction and background: Except for the early R stars, most carbon stars have spectra so densely occupied by bands of carbon compounds that nearly all the atomic lines that normally provide the criteria for spectral classification are either distorted or obliterated. It is this complexity that makes it so difficult to sort the spectra into types that can be calibrated in terms of fundamental physical variables: effective temperature (Teff), luminosity, and composition. Nevertheless, the authors have been able to assign temperature types, luminosity classes (at least for the R stars) and abundance indices for the principal compounds of carbon. The C2 index is included in the type for every carbon star; it seems to be the best measure of the ratio of carbon to oxygen. In using the index, allowance must be made for its sensitivity to temperature also. The C2 index runs from 1 to 5, indicating that the strong bands at 4737 and 5135 A are barely visible at the atlas scale. Other indices are included in the type only when it appears necessary to call attention to the behavior of a particular feature. Thus, for example, a CH index of 3.5 or greater defines a CH star. Since the relative strengths of the bands of carbon compounds containing the isotopes 12C and 13C differ widely in different kinds of carbon stars, an isotopic index, j, is used as a measure of 12C/13C. The index and its range from 1 to 5 agree with the usage of Yamashita (1972AnTok..13..169Y). Normally this index is included in the type only when j > 3.5 which defines an isotopic (or J) star. The relation of the index to isotopic ratio is shown in Table 1 of Barnbaum et al (1996ApJS..105..419B). Notation, however, is not the only problem. Both theory and observation have made it clear that an excess of carbon over oxygen can appear in te atmospheres of stars of different masses or original composition at different stages of their evolution. The new classification attempts to assign different spectral types to members of different spectroscopic groups.
Cone search capability for table J/ApJS/105/419/table4 (Catalog of standard stars on the Revised MK System)
