Ellis R. Holdenried

The Third US Naval Observatory CCD Astrograph Catalog (UCAC3)

The second US Naval Observatory (USNO) CCD Astrograph Catalog, UCAC2 was released in 2003 July. Positions and proper motions for 48,330,571 sources (mostly stars) are available on 3 CDs, supplemented with Two Micron All Sky Survey photometry for 99.5% of the sources. The catalog covers the sky area from -90° to +40° 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 (0.2 m) Twin Astrograph equipped with a 4K CCD camera. The precision of the positions are 15–70 mas, depending on magnitude, with estimated systematic errors of 10 mas or below. Proper motions are derived by using over 140 ground- and space-based catalogs, including Hipparcos/Tycho and the AC2000.2, as well as yet unpublished remeasures of the AGK2 plates and scans from the NPM and SPM plates. Proper-motion errors are about 1–3 mas yr-1 for stars to 12th magnitude, and about 4–7 mas yr-1 for fainter stars to 16th magnitude. The observational data, astrometric reductions, results, and important information for the users of this catalog are presented.

The First US Naval Observatory CCD Astrograph Catalog

The USNO CCD Astrograph (UCA) started an astrometric survey in 1998 February at Cerro Tololo, Chile. This first, preliminary catalog (UCAC1) includes data taken up to 1999 November with about 80% of the Southern Hemisphere covered. Observing continues, and full sky coverage is expected by mid-2003 after moving the instrument to a Northern Hemisphere site in early 2001. The survey is performed in a single bandpass (579–642 nm), a twofold overlap pattern of fields, and with a long and a short exposure on each field. Stars in the magnitude range 10–14 have positional precisions of ≤20 mas. At the limiting magnitude of R ≈ 16 mag, the positional precision is 70 mas. The UCAC aims at a density (stars per square degree) larger than that of the Guide Star Catalog (GSC) with a positional accuracy similar to Tycho. The UCAC program is a major step toward a high-precision densification of the optical reference frame in the post–Hipparcos era, and the first stage, the UCAC1 contains over 27 million stars. Preliminary proper motions are included, which were derived from Tycho-2, Hipparcos, and ground-based transit circle and photographic surveys for the bright stars (V ≤ 12.5 mag) and the USNO A2.0 for the fainter stars. The accuracy of the proper motions varies widely, from 1 to over 15 mas yr-1. The UCAC1 is available on CD-ROM from the US Naval Observatory.

SPECKLE INTERFEROMETRY OF NEW AND PROBLEM HIPPARCOS BINARIES. II. OBSERVATIONS OBTAINED IN 1998¨1999 FROM McDONALD OBSERVATORY

The Hipparcos satellite made measurements of over 9734 known double stars, 3406 new double stars, and 11,687 unresolved but possible double stars. The high angular resolution aUorded by speckle interferometry makes it an efficient means to con—rm these systems from the ground, which were —rst dis

SPECKLE INTERFEROMETRY AT THE US NAVAL OBSERVATORY. IX

The results of 3056 speckle interferometric observations of double stars, made with the 26 inch (66 cm) refractor of the US Naval Observatory, are presented. Each speckle interferometric observation of a system represents a combination of over a thousand short-exposure images. These observations are averaged into 1675 mean relative positions and range in separation from 019 to 4521, with a median separation of 299. This is the ninth in a series of papers presenting measures obtained with this system and covers the period 2002 January 1 through 2002 December 29. Included in these data are 28 older measures whose positions were previously deemed possibly aberrant but are no longer classified this way following a confirming observation. Nine of these systems have new orbital elements, which are presented here as well.

Speckle Interferometry at the US Naval Observatory. XII.

The results of 1657 speckle interferometric observations of double stars, made with the 26 inch (66 cm) refractor of the US Naval Observatory, are presented. Each speckle interferometric observation of a system represents a combination of over 2000 short-exposure images. These observations are averaged into 1111 mean relative positions and range in separation from 016 to 1699, with a median separation of 165. This is the 12th in a series of papers presenting measurements obtained with this system and covers the period 2005 January 3-December 29. Included in these data are 30 older measurements whose positions were previously deemed possibly aberrant but are no longer classified this way following a confirming observation. Sixteen of these systems have new orbital elements, which are presented here as well. For η Coronae Borealis (STF 1937) we determine masses of 1.207 and 1.077 M⊙ and an orbital parallax of 54.95 mas.

Speckle Interferometry at the US Naval Observatory. V.

The results of 1544 speckle interferometric observations of 637 binary stars, ranging in separation from 025 to 525, are tabulated. These observations were obtained using the 66 cm refractor at the US Naval Observatory in Washington, DC, with an intensified CCD detector. This is the fifth in a series of papers presenting measures obtained with this system and covers the period 1998 January 1 through December 31. Random errors for all measures are estimated to be 17.6 mas in separation and 055/ρ in position angle, where ρ is the separation in arcseconds.

Speckle Interferometry at the US Naval Observatory. VI.

The results of 1068 speckle interferometric observations of double stars, made with the 26 inch (0.66 m) refractor of the US Naval Observatory, are presented. These observations are averaged into 841 means of 815 binary stars. The systems range in separation from 022 to 601 with a mean separation of 221 and have a limiting secondary magnitude of V = 12.5. This is the sixth in a series of papers presenting measures obtained with this system, and it covers the period 1999 January 1 through 2000 January 9.

Speckle Interferometry at the US Naval Observatory. VIII.

The results of 2044 speckle interferometric observations of double stars, made with the 26 inch (66 cm) refractor of the US Naval Observatory, are presented. Each speckle interferometric observation of a system represents a combination of over a thousand short-exposure images. These observations are averaged into 1399 mean positions and range in separation from 016 to 1497, with a mean separation of 251. This is the eighth in a series of papers presenting measures obtained with this system and covers the period 2001 March 18 through 2001 December 30.

DOUBLE STARS IN THE TYCHO-2 CATALOGUE

The Tycho-2 Catalogue provides astrometric and photometric information for 2.5 million stars. Within the Tycho-2 Catalogue, while there is no separate listing of double-star parameters, there is a wealth of double-star data. For all measured double-star systems, each component has its own entry in Tycho-2 (this corresponds to the Hipparcos ii double-entry systems ˇˇ), and the classical double-star parameters of separation, position angle, and magnitude diUerence can be calculated for these systems. Most double stars in the Tycho-2 Catalogue are identi—ed by a code indicating a double, failed double, or photo- centric solution. Stars —agged in this manner include 6251 known double stars and 1234 new double-star systems (designated in the Washington Double Star Catalog (WDS) with a ii TDS ˇˇ discovery code). Also, 4726 systems solved via Tycho-2 ii single-star treatment ˇˇ not only matched one component of a WDS pair but also had a nearby star that closely approximated the position and magnitude of the other WDS component. Finally, 1133 WDS systems were seen as single in Tycho-2 whose historical double- star parameters would indicate that Tycho-2 should have measured them. The observational statistics of these various classes of objects are presented together with catalog statistics for those with single-star solutions. A quantitative assessment of Tycho-2 double-star measures is provided via a comparison of Tycho-2 O(C residuals to known orbits. Finally, a subset of systems measured by Tycho-2 have been veri—ed via speckle interferometry using the 82 inch (2 m) telescope of McDonald Observatory. These results are presented here.

Speckle Interferometry at the US Naval Observatory. VII.

The results of 2014 speckle interferometric observations of double stars, made with the 26 inch (66 cm) refractor of the US Naval Observatory, are presented. These observations are averaged into 1266 mean positions and range in separation from 021 to 1341, with a mean separation of 261. This is the seventh in a series of papers presenting measures obtained with this system and covers the period 2000 January 10 through December 8.