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OSU College of Arts and Sciences Department of Astronomy

The Revised Catalog of MK Spectra Types
for the Cooler Stars

Philip C. Keenan & Gerald H. Newsom
Department of Astronomy, The Ohio State University

Updated 2000 January 14

We regret to announce the death of Phillip C. Keenan on 2000 April 20 in Columbus, Ohio, at the age of 92. The contents of the tables below represent the state of the catalog on 1999 October 4.


This revision replaces the Perkins Catalog (Keenan & McNeil 1989) of standard stars classified on the Revised MK system. The purpose of the catalog is to provide observers working at any latitude with a set of consistent spectral types for stars later than GO. The Catalog is not a survey complete to any magnitude and is not intended for statistical studies.

The availability of the Hipparcos parallaxes (ESA 1997) has not only made possible a more accurate calibration of the luminosity classes of giants, but has also revealed some systematic departures from the original intent that class III should represent the main ridge of giants for types G, K and M. This aim has been realized by making slight modifications in the assignment of luminosity classes from the observed ratios of lines and bands that serve as criteria (Keenan & Barnbaum 1999).

For types G5 to K3 luminosity class IIIb defines members of the clump below the main giant branch. A few clump stars are still mis-classified as III. These are probably marginal barium stars, but since in low-resolution spectra it is not possible to detect slight strengthening of the lines of s-process elements resulting from abundance changes, we are not entitled to alter their apparent classes until spectra of resolution better than 1Å become available. In the catalog these suspect stars have a colon (:) after the luminosity classes.

The same ambiguity has been known for some time to exist at the upper edge of the giant branch (Keenan & Wilson 1977). Marginal barium stars of luminosity class III often look like normal stars of class III, IIIa, or even II, when observed at low resolution. Again, the catalog indicates such suspected barium stars by a colon following the luminosity class. The confirmed marginal barium stars are listed as such in the Catalog.

At the same time the Catalog has been extended to include S-stars and carbon stars, as well as a number of other stars newly classified, chiefly southern stars observed with the Garrison spectrograph on the Toronto telescope at Las Campanas. For the S-type stars the types given by Keenan & Boeshaar (1980) have been slightly simplified by listing both the Zr and Ti abundance indices after the temperature type (Keenan 1994). This makes the notation consistent with that of the other MK types. The spectral types for the carbon stars included in the catalog have been taken from the list of revised types of Barnbaum, Stone & Keenan (1996). As in earlier MK catalogs, the entries for stars considered to be the best determined spectral standards are preceded by plus signs (+).

We are grateful to Dr. Robert Garrison for making observing time available on the Toronto telescope at Las Campanas. A number of the spectrograms from there were taken by the Toronto resident observers.


ESA, 1997. The Hipparcos Catalog. ESA SP-1200
Keenan, P.C. 1994, ASP Conference Ser, 60, 15.
Keenan, P.C., & Wilson, O.C. 1977, ApJ, 214, 399
Keenan, P.C., & Boeshaar, P.C. 1980, ApJS, 43, 379
Keenan, P.C., & McNeil, R.C. 1989, ApJS, 71, 245
Keenan, P.C., & Barnbaum, C. 1999, ApJ, 518, 859

The Catalog

Updated 2000 Jan 14
ASCII Format (39Kb) [Not yet up to date]
HTML Format (270Kb)

Notes to the Catalog

Updated 1998 Oct 19
ASCII Format (9Kb)
HTML Format (9Kb)
Please see the Release Notes (1Kb ASCII text) for a summary of changes and updates to the catalog.