Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/381/446
- Title:
- Astrometric Radial Velocities. III.
- Short Name:
- J/A+A/381/446
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Astrometrically determined kinematic data are given for nearby clusters and associations, including astrometric radial velocities and kinematically improved parallaxes for individual stars. The astrometric radial velocities are determined independent of spectroscopy. Table 1 gives the space velocities and internal velocity dispersions of the clusters and associations. The electronic Table1 (Table1.dat) is an extended version of Table 1 in the journal paper, now including the full covariances of the space velocity components as well as the space motion in spherical coordinates. Table 2 gives the astrometric radial velocities and kinematically improved parallaxes for the individual stars. The electronic Table 2 is an extended version of Table 2 in the journal paper, now including all clusters and associations studied; results using data from both the Hipparcos and Tycho-2catalogues, as well as the standard errors for all deduced quantities. The electronic Table 2 is divided into 10 sub-tables (table1a.dat through table2j.dat), one for each cluster or association.
- 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/PAZh/27/456
- Title:
- Astrometric study of ADS 48
- Short Name:
- J/PAZh/27/456
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The series of relative positions of the hierarchical triple system ADS 48 ABF (AB=6",AF=327") obtained with the 26-inch Pulkovo refractor during 1961-1995 and measured with the Fantazia automated measuring system are analyzed.
- 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/AJ/161/204
- Title:
- Astrometry and photometry for 156 ZNG UV-bright stars
- Short Name:
- J/AJ/161/204
- Date:
- 09 Mar 2022 22:00:00
- Publisher:
- CDS
- Description:
- In 1972, Zinn, Newell, & Gibson (ZNG) published a list of 156 candidate UV-bright stars they had found in 27 Galactic globular clusters (GCs), based on photographs in the U and V bands. UV-bright stars lie above the horizontal branch (HB) and blueward of the asymptotic giant branch (AGB) and red giant branch in the clusters' color-magnitude diagrams. They are in rapid evolutionary phases-if they are members and not unrelated bright foreground stars. The ZNG list has inspired numerous follow-up studies, aimed at understanding late stages of stellar evolution. However, the ZNG candidates were presented only in finding charts, and celestial coordinates were not given. Using my own collection of CCD frames in u and V, I have identified all of the ZNG objects, and have assembled their coordinates, parallaxes, and proper motions from the recent Gaia Early Data Release 3 (EDR3). Based on the Gaia astrometry, I have determined which objects are probable cluster members (45% of the sample). For the members, using photometry from EDR3, I have assigned the stars to various evolutionary stages, including luminous post-AGB stars, and stars above the HB. I point out several ZNG stars of special interest that have still, to my knowledge, never been studied in detail. This study is an adjunct to a forthcoming survey of the Galactic GCs in the uBVI photometric system, designed for detection of low-gravity stars with large Balmer discontinuities.
- 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/660/1428
- Title:
- Astrometry around RX J0720.4-3125
- Short Name:
- J/ApJ/660/1428
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used a set of dedicated astrometric data from the Hubble Space Telescope to measure the parallax and proper motion of the nearby neutron star RX J0720.4-3125. At each of eight epochs over 2 years, we used the High Resolution Camera of the Advanced Camera for Surveys to measure the position of the B=26.6 target to a precision of ~2mas (~0.07pix) relative to 22 other stars. From these data we measure a parallax of plx=2.8+/-0.9mas (for a distance of 360^+170^_-90_pc) and a proper motion of mu=107.8+/-1.2mas/yr. Exhaustive testing of every stage of our analysis suggests that it is robust, with a maximum systematic uncertainty on the parallax of 0.4mas. The distance is compatible with earlier estimates made from scaling the optical emission of RX J0720.4-3125 relative to the even closer neutron star RX J1856.5-3754. The distance and proper motion imply a transverse velocity of 180^+90^_-40_km/s, comparable to velocities observed for radio pulsars. The speed and direction suggest an origin for RX J0720.4-3125 in the Trumpler 10 OB association ~0.7Myr ago, with a possible range of 0.5-1.0Myr given by the uncertainty in the distance.
