Spectrophotometry of cool carbon stars

1 August 1977

journal article
research article
Published by IOP Publishing in Publications of the Astronomical Society of the Pacific

Vol. 89 (530) , 510
https://doi.org/10.1086/130153

Abstract

Observations of 75 carbon stars have been made with the Indiana rapid spectrum scanner covering a wavelength range of 5000 A-7000 A at 30-A resolution. The data have been used to form molecular indices for a quantitative measurement of the strength of the C2 Swan system and the shape of the CN red (6, 1) band sequence which is sensitive to the C-12/C-13 isotope ratio. The C2 strength is plotted against the strength of CN and CO; the observed band strengths are found to behave as would be expected from model-atmosphere calculations. Using C/O ratios from Kilston (1975) it is possible to calculate the observed CN/C2 ratio and determine photometric C/O ratios for 61 cool carbon stars. The CN red (6, 1) band photometry shows that only a few (25%) of cool carbon stars have C-12/C-13 isotope ratios significantly lower than the majority of cool carbon stars.

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