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Improved Astrometry and Photometry for the Luyten Catalog. II. Faint Stars and the Revised Catalog
We complete construction of a catalog containing improved astrometry andnew optical/infrared photometry for the vast majority of NLTT starslying in the overlap of regions covered by POSS I and by the secondincremental Two Micron All Sky Survey (2MASS) release, approximately 44%of the sky. The epoch 2000 positions are typically accurate to 130 mas,the proper motions to 5.5 mas yr-1, and the V-J colors to0.25 mag. Relative proper motions of binary components are measured to 3mas yr-1. The false-identification rate is ~1% for11<~V<~18 and substantially less at brighter magnitudes. Theseimprovements permit the construction of a reduced proper-motion diagramthat, for the first time, allows one to classify NLTT stars intomain-sequence (MS) stars, subdwarfs (SDs), and white dwarfs (WDs). We inturn use this diagram to analyze the properties of both our catalog andthe NLTT catalog on which it is based. In sharp contrast to popularbelief, we find that NLTT incompleteness in the plane is almostcompletely concentrated in MS stars, and that SDs and WDs are detectedalmost uniformly over the sky δ>-33deg. Our catalogwill therefore provide a powerful tool to probe these populationsstatistically, as well as to reliably identify individual SDs and WDs.
| UV Spectral Classification of O and B Stars in the Small Magellanic =
We present an ultraviolet classification system for 0 and B stars of theSmall Magellanic Cloud (SMC). This system is defined by a set ofstandard, low resolution, International Ultraviolet Explorer (JUE)spectra. This UV classification system results from the development ofspectral sequences demonstrating systematic patterus of UV spectralfeatures. These spectral sequences yield Uv classifications for 133 0and B stars of the SMC, which we also present here. Although independentof the MK System, our UV classifications show general agreement withthose deduced from visual data. This UV classification system isdesigned to be applicable to 0 and B stars in other nearby galaxies ofmetallicity comparable to the SMC. The classification technique itselfis applicable to any UV dataset of sufficient size and quality, and canbe used to extend our UV classification system to other galactic metalabundances. These UV classification systems will be essential foranalysis of datasets from new spaceborne instrumentation such as theSpace Telescope Imaging Spectrograph (STIS), which will be capable ofobserving stars in external galaxies for which no opticalclassifications exist. 0 1997 American Astronomical Society.[S0004-6256(97)0231 1-X]
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