Revised Coordinates and Proper Motions of the Stars in the Luyten Half-Second Catalog

We present refined coordinates and proper-motion data for the high proper-motion (HPM) stars in the Luyten Half-Second (LHS) catalog. The positional uncertainty in the original Luyten catalog is typically greater than 10" and is often greater than 30". We have used the digital scans of the POSS I and POSS II plates to derive more accurate positions and proper motions of the objects. Out of the 4470 candidates in the LHS catalog, 4323 objects were manually reidentified in the POSS I and POSS II scans. A small fraction of the stars were not found because of the lack of finder charts and digitized POSS II scans. The uncertainties in the revised positions are typically ~2" but can be as high as ~8" in a few cases, which is a large improvement over the original data. Cross-correlation with the Tycho-2 and Hipparcos catalogs yielded 819 candidates (with m_R<~12). For these brighter sources, the position and proper-motion data were replaced with the more accurate Tycho-2/Hipparcos data. In total, we have revised proper-motion measurements and coordinates for 4040 stars and revised coordinates for 4330 stars. The electronic version of the paper5 contains the updated information on all 4470 stars in the LHS catalog.