A Comparision of B-Star Spectral Types on the MK and Ultraviolet Classification Systems

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Session 80 -- Stellar Activity II: Early Type Stars, Normal Stars
Display presentation, Wednesday, 11, 1995, 9:20am - 6:30pm

[80.04] A Comparision of B-Star Spectral Types on the MK and Ultraviolet Classification Systems

J. Rountree (SAIC/U. Arizona), G. Sonneborn (NASA/GSFC)

Rountree and Sonneborn (1991, ApJ 369, 515, Paper I) established a set of criteria for the classification of B-type spectra in the ultraviolet, using MK standards and photospheric absorption lines in the 1200-1900 A region. They predicted that spectral types of B-type dwarfs, subgiants and giants classified on this system would be equivilant to optical MK types. Spectra of more than 100 additional stars, not used in the definition of the system, have been classified using the criteria and standards of Paper I. Some of these spectra have already been published in the ultraviolet Atlas of B-Type Spectra by Rountree and Sonneborn (1993, NASA Ref. Pub. 1312). Like the original set, these data were drawn from the IUE archives of high-dispersion, short-wavelength spectra. They were resampled and processed as described in Paper I. Each new spectrum was classified with no prior knowledge of the star's identity of its optical MK type, except that the sample was known to be composed of B stars, and in principal did not contain any supergiants or Be stars. The new ultraviolet types were then compared to with the optical MK types. There were no systematic differences, either in temperature type or luminosity class, for B0-B5 spectra. Mean errors were less than one-half spectral subtype or one luminosity class. Later B stars tended to have larger errors and to be classified systematically too early and/or too bright. The B8 stars were proorly represented in the sample and were not included in the error statistics.

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