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Mapping the Local Galactic Halo. I. Optical Photometry of Cool Subdwarf Candidates
Optical (BVRI) photometric measurements of a sample of 564 candidatecool subdwarfs in the nearby halo are presented. The stars generallyspan the color range 0.4<(B-V)<1.8 hence, the sample is composedof early F- through early M-type stars on the subdwarf sequence. Thesample is selected from the revised NLTT catalog of Gould and Salim andSalim and Gould via a reduced proper motion diagram. The photometry isprecise and accurate; in particular, for stars with 9
| 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.
| Early-type stars detected on UK Schmidt objective-prism plates - III. UKST area 881.
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Gözlemler ve gökölçümü verileri
| Takýmyýldýz: | Kartal |
| Sað Açýklýk: | 19h10m05.13s |
| Yükselim: | -00°58'38.8" |
| Görünürdeki Parlaklýk: | 9.933 |
| özdevim Sað Açýklýk: | -24.3 |
| özdevim Yükselim: | -173.3 |
| B-T magnitude: | 10.173 |
| V-T magnitude: | 9.953 |
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