- ID:
- ivo://CDS.VizieR/I/171
- Title:
- Astrographic Catalog Reference Stars (ACRS)
- Short Name:
- I/171
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ACRS is an all-sky catalog of positions and proper motions that is based on the AGK3 in the north and on the newly completed second Cape Photographic Catalogue (CPC2, de Vegt et al. 1989) in the south. The astrometric data are on the system of the International Reference Stars (IRS, catalog <I/172>), compiled on B1950.0 FK4 and then transformed to J2000.0 FK5. The ACRS contains 320,111 stars, the mean positions for which were derived from a total of 1,643,783 individual input positions. The catalog is divided into two parts. Part 1 contains stars having better observational histories and, therefore, more reliable positions and proper motions, while the stars in Part 2 have poor histories and consist mostly of objects for which only two catalog positions in one or both coordinates were available for computing proper motions. For Part 1, which consists of 78 percent of the catalog, the mean errors of the proper motions in right ascension and declination are 0.47 and 0.46 seconds of arc/century (4.7 and 4.6 mas/yr), respectively. It is intended that, as more observations are accumulated for stars in Part 2, they will be migrated to Part 1. The catalog was compiled at the U.S. Naval Observatory, Washington, D.C., for purposes of performing new reductions of the Astrographic Catalogue plates. Additional details about the construction of the ACRS may be found in Corbin and Urban (1989). The data included are catalog part, ACRS number, equatorial coordinates (equinox, equator, epoch B1950.0 and J2000.0), proper motions (B1950.0 and J2000.0), original epochs, weights for right ascension and declination, and reference data such as DM numbers (BD, CD, CPD), AGK3 and CPC2 designations, and an IAU recommended ACRS identifier (based on coordinates).
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/565/A21
- Title:
- Astrometric catalog around ultracool dwarfs
- Short Name:
- J/A+A/565/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the astrometric reduction of images obtained with the FORS2/VLT camera in the framework of an astrometric planet search around 20 M/L-transition dwarfs. We present the correction of systematic errors, the achieved astrometric performance, and a new astrometric catalogue containing the faint reference stars in 20 fields located close to the galactic plane. Remote reference stars are used both to determine the astrometric trajectories of the nearby planet search targets and to identify and correct systematic errors. We detected three types of systematic errors in the FORS2 astrometry: the relative motion of the camera's two CCD chips, errors that are correlated in space, and an error contribution of yet unexplained origin. The relative CCD motion has probably a thermal origin and usually is 0.001-0.010px (0.1-1mas), but sometimes amounts to 0.02-0.05px (3-6mas). This instability and space- correlated errors are detected and mitigated using reference stars. The third component of unknown origin has an amplitude of 0.03-0.14mas and is independent of the observing conditions. We find that a consecutive sequence of 32 images of a well-exposed star over 40min at 0.6arcsec seeing results in a median r.m.s. of the epoch residuals of 0.126mas. Overall, the epoch residuals are distributed according to a normal law with a {chi}^2^ value near unity. We compiled a catalogue of 12000 stars with I-band magnitudes of 16-22 located in 20 fields, each covering 2x2'. It contains I-band magnitudes, ICRF positions with 40-70mas precision, and relative proper motions and absolute trigonometric parallaxes with a precision of 0.1mas/yr and 0.1mas at the bright end, respectively. This work shows that an astrometric accuracy of ~100 micro-arcseconds over two years can be achieved with a large optical telescope in a survey covering several targets and varying observing conditions.
- ID:
- ivo://CDS.VizieR/I/332
- Title:
- Astrometric catalogue of stars KMAC2
- Short Name:
- I/332
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of astrometric observations of faint V<17mag stars obtained with the Kyiv meridian axial circle. Observations were carried out in 2001-2005 in a declination zone of 0+2 degrees and with use of Johnson V-band filter. The catalogue contains data for about a million of stars.
- ID:
- ivo://CDS.VizieR/J/A+A/642/A21
- Title:
- Astrometric parameters for 135 OB stars
- Short Name:
- J/A+A/642/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our goal is to better understand the origin and the star-formation history of regions NGC 6334 and NGC 6357. We focus our study on the young stars (young stellar objects and OB stars) kinematics in both regions using mainly Gaia-DR2 data. For both regions we compiled OB stars and young stellar objects catalogues from literature and we complemented them using VPHAS+ DR2 and Spitzer IRAC/GLIMPSE photometry catalogues. A cross-match is performed with the Gaia-DR2 catalogue in order to obtain the parallax and transverse motion information. We confirm that NGC 6334 and NGC 6357 are in the far side of the Saggitarius-Carina arm at a distance of 1.76kpc. For NGC 6357, OB stars show strong clustering and ordered star motion with Vlon~-10.7km/s and Vlat ~3.7km/s while for NGC 6334, no significant systemic motion is observed. The OB stars motions and distribution in NGC 6334 suggest to classify it as an association. Ten and two runaway candidates can be related to NGC 6357 and NGC 6334, respectively. The spatial distributions of the runaway candidates in and around NGC 6357 favor a dynamical (and early) ejection during the cluster(s) formation. Because such stars are likely to be ejected during cluster's formation the fact of not observing as many of such stars towards NGC 6334 suggest different formation conditions than for NGC 6357.
- ID:
- ivo://CDS.VizieR/J/AJ/136/452
- Title:
- Astrometric studies of GAT stars
- Short Name:
- J/AJ/136/452
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of astrometric studies in the regions of Groombridge 34A, the Hyades, Aldebaran, Ross 47, BD+5 1668, 81 Cancri, BD+15 2620, Arcturus, Vega, and Ross 248 are presented. Estimates of the absolute parallax of each star are presented and a mass estimate is present for 81 Cancri. Comments include the discussion of the apparent motions of a few previously suggested planetary systems.
- ID:
- ivo://CDS.VizieR/J/AJ/126/2922
- Title:
- Astrometry and membership in NGC 188
- Short Name:
- J/AJ/126/2922
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present techniques for obtaining precision astrometry using old photographic plates from assorted large-aperture reflectors in combination with recent CCD Mosaic Imager frames. At the core of this approach is a transformation of plate/CCD coordinates into a previously constructed astrometric reference frame around the open cluster NGC 188.
- ID:
- ivo://CDS.VizieR/J/ApJ/718/810
- Title:
- Astrometry and Photometry in the Arches cluster
- Short Name:
- J/ApJ/718/810
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Deep Keck/NIRC2 HK'L' observations of the Arches cluster near the Galactic center reveal a significant population of near-infrared excess sources. We combine the L'-band excess observations with K'-band proper motions, which allow us to confirm cluster membership of excess sources in a starburst cluster for the first time. The robust removal of field contamination provides a reliable disk fraction down to our completeness limit of H=19mag, or ~5M_{sun}_ at the distance of the Arches. Of the 24 identified sources with K'-L'>2.0mag, 21 have reliable proper motion measurements, all of which are proper motion members of the Arches cluster. VLT/SINFONI K'-band spectroscopy of 3 excess sources reveals strong CO bandhead emission, which we interpret as the signature of dense circumstellar disks. The detection of strong disk emission from the Arches stars is surprising in view of the high mass of the B-type main sequence host stars of the disks and the intense starburst environment. We find a disk fraction of 6%+/-2% among B-type stars in the Arches cluster. A radial increase in the disk fraction from 3% to 10% suggests rapid disk destruction in the immediate vicinity of numerous O-type stars in the cluster core. A comparison between the Arches and other high- and low-mass star-forming regions provides strong indication that disk depletion is significantly more rapid in compact starburst clusters than in moderate star-forming environments.
- ID:
- ivo://CDS.VizieR/J/AJ/145/136
- Title:
- Astrometry and photometry of nearby white dwarfs
- Short Name:
- J/AJ/145/136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the preliminary results of a survey aimed at significantly increasing the range and completeness of the local census of spectroscopically confirmed white dwarfs. The current census of nearby white dwarfs is reasonably complete only to about 20pc of the Sun, a volume that includes around 130 white dwarfs, a sample too small for detailed statistical analyses. This census is largely based on follow-up investigations of stars with very large proper motions. We describe here the basis of a method that will lead to a catalog of white dwarfs within 40pc of the Sun and north of the celestial equator, thus increasing by a factor of eight the extent of the northern sky census. White dwarf candidates are identified from the SUPERBLINK proper motion database, allowing us to investigate stars down to a proper motion limit {mu}>40mas/yr, while minimizing the kinematic bias for nearby objects. The selection criteria and distance estimates are based on a combination of color-magnitude and reduced proper motion diagrams. Our follow-up spectroscopic observation campaign has so far uncovered 193 new white dwarfs, among which we identify 127 DA (including 9 DA+dM and 4 magnetic), 1 DB, 56 DC, 3 DQ, and 6 DZ stars. We perform a spectroscopic analysis on a subsample of 84 DAs, and provide their atmospheric parameters. In particular, we identify 11 new white dwarfs with spectroscopic distances within 25pc of the Sun, including five candidates to the D<20pc subset.
- ID:
- ivo://CDS.VizieR/J/AJ/146/76
- Title:
- Astrometry and photometry of UCAC4 double stars
- Short Name:
- J/AJ/146/76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The newly completed Fourth USNO CCD Astrographic Catalog (UCAC4) has proven to be a rich source of double star astrometry and photometry. Following initial comparisons of UCAC4 results against those obtained by speckle interferometry, the UCAC4 catalog was matched against known double stars in the Washington Double Star Catalog in order to provide additional differential astrometry and photometry for these pairs. Matches to 58131 pairs yielded 61895 astrometric and 68935 photometric measurements. Finally, a search for possible new common proper motion (CPM) pairs was made using new UCAC4 proper motion data; this resulted in 4755 new potential CPM doubles (and an additional 27718 astrometric and photometric measures from UCAC and other sources).
- ID:
- ivo://CDS.VizieR/J/ApJ/725/331
- Title:
- Astrometry in the Galactic Center
- Short Name:
- J/ApJ/725/331
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present significantly improved proper motion measurements of the Milky Way's central stellar cluster. These improvements are made possible by refining our astrometric reference frame with a new geometric optical distortion model for the W. M. Keck II 10m telescope's adaptive optics camera (NIRC2) in its narrow field mode. For the first time, this distortion model is constructed from on-sky measurements and is made available to the public in the form of FITS files. When applied to widely dithered images, it produces residuals in the separations of stars that are a factor of ~3 smaller compared with the outcome using previous models. By applying this new model, along with corrections for differential atmospheric refraction, to widely dithered images of SiO masers at the Galactic center (GC), we improve our ability to tie into the precisely measured radio Sgr A*-rest frame. The resulting infrared reference frame is ~2-3 times more accurate and stable than earlier published efforts. In this reference frame, Sgr A* is localized to within a position of 0.6mas and a velocity of 0.09mas/yr, or ~3.4km/s at 8kpc (1{sigma}). Also, proper motions for members of the central stellar cluster are more accurate, although less precise, due to the limited number of these wide field measurements. We define a reference frame with SiO masers and this reference frame's stability should improve steadily with future measurements of the SiO masers in this region ({propto}t^-3/2^). This is essential for achieving the necessary reference frame stability required to detect the effects of general relativity and extended mass on short-period stars at the GC.
