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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.
| The influence of convection and rotation on X-ray emission in main sequence stars
The dependence of X-ray luminosity on rotation rate and other parametersrelevant to the creation of enhanced magnetic regions is investigated.The role of the Rossby number as a measure of interaction between flowvelocities and rotation is considered, and some useful correlationsbetween this number and the X-ray luminosity are shown. The significanceof these results are considered and a physical conclusion is derived asto the unity of the mechanism generating the magnetic field along thewhole spectral sequence.
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Osservazione e dati astrometrici
| Costellazione: | Balena |
| Ascensione retta: | 01h31m34.99s |
| Declinazione: | -13°41'24.4" |
| Magnitudine apparente: | 8.878 |
| Distanza: | 77.34 parsec |
| Moto proprio RA: | 24.9 |
| Moto proprio Dec: | -188.6 |
| B-T magnitude: | 9.722 |
| V-T magnitude: | 8.948 |
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