Completeness of USNO-B for High Proper-Motion Stars

Abstract

I test the completeness of USNO-B detections of high proper-motion (mu>0.18"/yr) stars and the accuracy of its measurements by comparing them to the revised NLTT (rNLTT) catalog of Salim & Gould. For 14.5<V<18.5, only 6% of such stars are missing from USNO-B while another 4% have large errors, mostly too large to be useful. Including both classes, incompleteness is 10%. These fractions rise toward both brighter and fainter magnitudes. Incompleteness rises with proper motion to about 30% at mu=1"/yr. It also rises to about 35% at the Galactic plane, although this is only determined for relatively bright stars V<~14. For binaries, incompleteness rises from 10% at separations of 30" to 47% at 10". The proper-motion errors reported internally by USNO-B are generally correct. However, there is floor of sigma_mu~4mas/yr below which the reported errors should not be taken at face value. The small number of stars with relatively large reported errors (sigma_mu>~20mas/yr) may actually have still larger errors than tabulated.Comment: Submitted to AJ, 26 pages including 10 figure