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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.
| Magnitude, color and spectral type of AQL X-1 in quiescence
Direct I and V-band imaging of Aql X-1 in quiescence and during outburstmaximum shows that the true optical counterpart is the interloperlocated 0.48'' West of the previously known star. We find for the newcounterpart V = 21.6 and V-I = 2.2 in quiescence, when its contributionto the total light was 12% in V and 22% in I. Analysis of thisphotometry and of low-resolution spectra of the sum of both stars, alsotaken during quiescence, shows that the likely spectral types for thepreviously known star and the optical counterpart are late G and late K,respectively, reddened by E(B-V) = 0.5+/-0.1. Based on observationsobtained at the European Southern Observatory, La Silla, Chile
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Pozíciós és asztrometriai adatok
| Csillagkép: | Déli Korona |
| Rektaszcenzió: | 18h21m11.46s |
| Deklináció: | -38°40'56.0" |
| Vizuális fényesség: | 9.306 |
| RA sajátmozgás: | -141.7 |
| Dec sajátmozgás: | -181.9 |
| B-T magnitude: | 10.122 |
| V-T magnitude: | 9.374 |
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