THE ASTROPHYSICAL JOURNAL, 446:300-317, 1995 June 10

          NEURAL NETWORK CLASSIFICATION OF THE NEAR-INFRARED SPECTRA
                                OF A-TYPE STARS

                   WM. BRUCE WEAVER AND ANA V. TORRES-DODGEN
             Monterey Institute for Research in Astronomy (MIRA),
                  900 Major Sherman Lane, Monterey, CA 93940


                                   ABSTRACT

        We present an atlas of near-infrared (NIR) spectra of A stars for
     luminosity classes Ia through V in the 15 A resolution system
     described by Torres-Dodgen and Weaver (1993, PASP, 105, 693) and
     demonstrate an accurate method to automatically classify A stars on
     this system.  Using equivalent widths, artificial neural networks
     (ANNs) can classify these spectra to an accuracy of 0.4 types
     (subclasses) in temperature and 0.15 classes in luminosity.  Using the
     spectrum, with no manual intervention except wavelength registration,
     ANNs can classify these spectra with an accuracy comparable to that of
     2 A resolution MK classification: 0.5 types in temperature and 0.35
     classes in luminosity. In addition, ANNs can concurrently determine
     reddening to an accuracy of 0.05 in E(B-V).  We demonstrate that this
     NIR-ANN spectral classification system has the primary properties
     needed for automated classification surveys: it is based in the most
     efficient spectral region of modern silicon-based detectors, it
     requires low resolution (15 A) spectra to achieve sub-classification
     box accuracy, it can produce two dimensional classifications at least
     as accurate as those by expert human classifiers, it is relatively
     insensitive to interstellar reddening and can accurately determine the
     reddening, it can identify and classify composite spectra, it degrades
     slowly with decreasing signal-to-noise ratio, and it requires a
     minimum of human interaction at all stages of the process.


     Subject headings: atlases -- dust, extinction -- infrared: stars --
                       stars: fundamental parameters -- techniques: 
                       spectroscopic