Theodore J. Rafferty

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derived by using over 140 ground- and space-based catalogs, including Hipparcos/Tycho and the AC2000.2, as well as yet unpublished remeasures of the AGK2 plates and scans from the NPM and SPM plates.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. X.

The results of 3047 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 1572 mean relative positions and range in separation from 020 to 6286, with a median separation of 419. This is the 10th in a series of papers presenting measures obtained with this system and covers the period 2003 January 13 through 2003 December 1. Included in these data are nine older measures whose positions were previously deemed possibly aberrant but are no longer classified this way following a confirming observation. Four of these systems have new orbital elements, which are presented here as well.

SPECKLE INTERFEROMETRY AT THE USNO FLAGSTAFF STATION: OBSERVATIONS OBTAINED IN 2003-2004 AND 17 NEW ORBITS

Results are presented for 353 speckle interferometric observations of double stars, obtained in 2003 and 2004 at the USNO Flagstaff Station using the 1.55 m Kaj Strand Astrometric Reflector. Separations range from 012 to 742, with a median of 042. These two observing runs concentrated on systems in need of improved orbital elements, and new solutions have been determined for 17 systems as a result.

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.

Optical Positions of ICRF Sources Using UCAC Reference Stars

New optical positions on the 30 mas precision level have been obtained for 172 extragalactic International Celestial Reference Frame (ICRF) sources mainly in the range -30° ≤ δ ≤ +25°. Results are presented from a pilot investigation including four Cerro Tololo (CTIO) 0.9 m runs (1999–2001). Reference stars in the R ≈ 10–16.5 mag range from a preliminary US Naval Observatory CCD Astrograph Catalog (UCAC) are used. Systematic errors have been investigated, and a field distortion pattern based on the residuals has been removed. The errors of the fainter stars in the CTIO data were assessed by evaluating an auxiliary set of CCD observations of common ICRF sources, taken at the 1.60 m Cassegrain telescope of the Laboratorio Nacional de Astrofisica, Brazil. A significant improvement in the optical positions was achieved over a previous determination of source positions. The mean optical positions are compared with the ICRF radio positions. The overall optical minus radio offsets are -6 and -15 mas for right ascension and declination, respectively. The formal internal error of these mean offsets is ≈2.3 mas. This indicates a possible systematic error in the UCAC declinations of ≈10 to 15 mas. Both the optical counterpart observations and the optical reference stars are observed about 9 yr after the Hipparcos mean epoch, and our results set an upper limit for a possible Hipparcos system rotation with respect to the International Celestial Reference System for the z-axis of about 0.7 mas yr-1.

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. XI

The results of 1683 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 805 mean relative positions and range in separation from 023 to 4334, with a median separation of 433. This is the 11th in a series of papers presenting measurements obtained with this system and covers the period 2004 January 4-December 30. Included in these data are two older measurements whose positions were previously deemed possibly aberrant but are no longer classified this way following a confirming observation. Two of these systems have new orbital elements, which are also presented here.