Improved astrometry and photometry for the Luyten catalog. II. Faint stars and the revised catalog.
SALIM S. and GOULD A.
Abstract (from CDS):
We complete construction of a catalog containing improved astrometry and new optical/infrared photometry for the vast majority of NLTT stars lying in the overlap of regions covered by POSS I and by the second incremental 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 to 0.25 mag. Relative proper motions of binary components are measured to 3 mas.yr–1. The false-identification rate is ∼1% for 11≲V≲18 and substantially less at brighter magnitudes. These improvements permit the construction of a reduced proper-motion diagram that, for the first time, allows one to classify NLTT stars into main-sequence (MS) stars, subdwarfs (SDs), and white dwarfs (WDs). We in turn use this diagram to analyze the properties of both our catalog and the NLTT catalog on which it is based. In sharp contrast to popular belief, we find that NLTT incompleteness in the plane is almost completely concentrated in MS stars, and that SDs and WDs are detected almost uniformly over the sky δ>-33°. Our catalog will therefore provide a powerful tool to probe these populations statistically, as well as to reliably identify individual SDs and WDs.