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Published February 1990 | Published
Journal Article Open

Classification of Very Red Stars Using Narrowband Colors


A classification technique for faint, very red stars is described, based on two composite colors, derived from flux measurements in six narrowbands in the visual and red parts of the spectrum. One of the composite colors, ST, is an M spectral type indicator, common to both dwarfs and giants. It can be used to predict the spectral types to within half a class. The other color, DG, is a dwarf-giant discriminator for spectral types later than about M4, and whose power increases for the later types, where most other methods fail. It reflects the differences in blanketing between the late-M type dwarfs and the giants. The method can be generalized to other, similar colors, depending on the data and task at hand. It should be useful in surveys for extreme low-mass dwarfs, or alternatively, for luminous red giants, or other kinds of objects. We illustrate the application of the method on an example of a very red star identified earlier by Blair and Long, and show it to be a distant red giant.

Additional Information

© 1990 American Astronomical Society. Provided by the NASA Astrophysics Data System. Received 7 August 1989, revised 27 October 1989. It is a pleasure to thank the staff of Palomar Observatory for their expert assistance at the telescope, in particular to Juan Carrasco, Dave Tennant, and John Henning, and to Charles Evans for assistance with the observations of the Blair-Long star. We are grateful to Jim Gunn for the detailed printout of his multichannel spectrophotometry, to Bev Oke for data on the dM's taken with the Double Spectrograph, and to Jim Gunn, Maarten Schmidt, and Don Schneider for 4-Shooter output on the faintest dM's. We also acknowledge very illuminating discussions with Jim Liebert. We thank the referee for directing us to several useful references about the related previous work. This work was supported in part by Alfred P. Sloan Foundation and California Institute of Technology (S.D.), and by a Special Caltech Institute Fellowship (D.J.T.).

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Published - 1990AJ_____99__684D.pdf


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