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R. F. Wing (Ohio State University)
A six-color (6c) system of narrow-band photometry, closely related to the author's eight-color (8c) photomultiplier system but modified to permit observations with a CCD detector, has been established. Both systems are intended to provide two-dimensional (temperautre/luminosity) spectral classifications for oxygen-rich stars later than type K4 by measuring near-infrared continuum points and strong bands of TiO and CN (and also VO in stars of types M6 and later). The new filters are circular and 50 mm in diameter to take advantage of the imaging capabilities of the CCD. The filters centered at 7120 Å(TiO), 7540 Å(continuum), 7810 Å(weak TiO; C--star continuum), and 8120 Å(CN) have FWHM widths of 40--60 Åand are essentially identical to their counterparts on the 8c system. Because of the rapidly decreasing sensitivity of typical CCDs at wavelengths beyond 10000 Å, the filters at 10350 Å (continuum) and 10560 Å(VO) were widened to 100 Åbut serve the same purposes as on the 8c system. For the same reason, the two filters of longest wavelength on the 8c system, which measure the (0,0) band of CN, had to be abandoned on the 6c system. A new set of equatorial standard stars, approximately 2 mag fainter than the 8c photomultiplier standards, were selected from the lists of Landolt standards and have been tied to the 8c standards through observations with the CTIO/SMARTS 0.9-m telescope.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.