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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.
| Light variations of massive stars (Alpha Cygni variables). XII - The photometric history of the G8Ia(+) hypergiant V766 CEN (= HR 5171A) during the years 1953-1991 and its interpretation
VBLUW photometry of the G8 Ia(+) hypergiant V 766 Cen (= HR 5171A) madein the interval 1980-1991 is presented and discussed, together with UBVphotometry taken from the literature, which goes back in time until1953. The star shows a very strong reddening of about 0.65 m between1953 and 1981, a brightness oscillation with a quasi-period of 494 d, inthe interval 1973-1991, and a drop in brightness between 1973 and 1977.Whether the strong reddening is caused by an increasing circumstellardust density or by evolution to the red in the HR diagram is discussed.The radial velocity curve (1979-1981) appears to be in phase with thelight curve. This peculiar behavior is shared with the variable F-typesupergiant BL Tel(F). The radius variation amounts to about 8 percent.
| Five-channel photometry of cepheids and supergiants in the southern Milky Way.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976A&AS...24..413P&db_key=AST
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