The Second US Naval Observatory CCD Astrograph Catalog (UCAC2)

Abstract

The second USNO CCD Astrograph Catalog, UCAC2 was released in July 2003. Positions and proper motions for 48,330,571 sources (mostly stars) are available on 3 CDs, supplemented with 2MASS photometry for 99.5% of the sources. The catalog covers the sky area from −90 • to +40 • degrees declination, going up to +52 • in some areas; this completely supersedes the UCAC1 released in 2001. Current epoch positions are obtained from observations with the USNO 8-inch Twin Astrograph equipped with a 4k CCD camera. The precision of the positions are 15 to 70 mas, depending on magnitude, with estimated systematic errors of 10 mas or below. Proper motions are derived by utilizing over 140 ground-and space-based catalogs, including Hipparcos/Tycho, the AC2000.2, as well as yet unpublished re-measures of the AGK2 plates and scans from the NPM and SPM plates. Proper motion errors are about 1 to 3 mas/yr for stars to 12th magnitude, and about 4 to 7 mas/yr for fainter stars to 16th magnitude. The observational data, astrometric reductions, results, and important information for the users of this catalog are presented.

Binary frequency of planet-host stars at wide separations

“…The survey ended at the beginning of 2001, providing a final world-public catalogue of ∼471 million sources (Cutri et al 2003). Comparison of the 2MASS catalogue with other catalogues such as Tycho-2 (Høg et al 2000) and UCAC (Zacharias et al 2003) indicate that 2MASS positions in the International Celestial Reference System are accurate to 70−80 mas (root-mean-square; rms) over most of the magnitude range (K s between 6 and 15 mag). This all-sky survey played a major role in astronomy over the past decade, in particular in our knowledge of the low-mass and substellar populations of the solar neighbourhood (e.g.…”

WASP 1628+10 – an EL CVn-type binary with a very low mass stripped red giant star and multiperiodic pulsations

“…Near-ultraviolet (NUV) and far-ultraviolet (FUV) photometry was obtained from the GALEX GR6 catalogue 5 (Morrissey et al 2007). Optical photometry was obtained from the NOMAD catalogue 6 (Zacharias et al 2004). Near-infrared photometry was obtained from the 2MASS 7 and DENIS 8 catalogues (Skrutskie et al 2006;The DENIS Consortium 2005).…”

The Tycho-2 Catalogue: a reference for astrometry and photometry. Combining the most modern and the oldest astrometric data

“…It is impressive to see that the number of interrogations is increasing, with a maximum of 600 000 and an average of 230 000 per month. These numbers can be compared to similar numbers for the main Hipparcos Catalogue (Perryman et al 1997): max 940 000, average 280 000, and for the UCAC2 Catalogue (Zacharias et al 2004), which is the astrometric reference catalog for stars down to magnitude 16: max 220 000, Article published by EDP Sciences average 63 000. Another noticeable effect is that the interrogation statistics of these three catalogs exhibit very similar behavior with a parallel and strong increase from 2008.…”