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[49.01] Narrow-Band Photometry of Red Supergiants in the Small Magellanic Cloud

R.F. Wing, K.M. Walker (OSU), E. Costa (U. de Chile), M.L. Houdashelt (JHU), D.J. MacConnell (CSC/STScI)

A set of 36 red supergiants belonging to the Small Magellanic Cloud have been observed on a six-color narrow-band photometric system that measures continuum points and bands of TiO and CN, all in the near-infrared. The TiO--based spectral types range from The absolute magnitudes M_V and M(104), based on a distance modulus of 18.9 mag and a very small correction for interstellar absorption, imply that the stars observed are Ia and Iab supergiants. Their CN--based luminosity classes, however, are mostly Ib. The difference is attributed to the effect of the lower metallicity of the SMC, relative to the Population I stars of the Milky Way, on the observed CN strength. These observations allow us to express the CN/luminosity calibration as a function of metallicity, thereby enhancing the usefulness of red supergiants as distance indicators for nearby galaxies of known metallicity.

The observations were made at Cerro Tololo Inter-American Observatory.

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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.