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151. Errors in the FK5 Catalog
ID:
ivo://CDS.VizieR/J/AJ/114/850
Title:
Errors in the FK5 Catalog
Short Name:
J/AJ/114/850
Date:
21 Oct 2021
Publisher:
CDS
Description:
This paper presents new positions for 689 FK5 stars determined directly in the extragalactic reference system from CCD scan observations made with the Flagstaff Astrometric Scanning Transit Telescope (FASTT). All the observations were made in 1994-1996 with an accuracy of ~+/-40mas in each coordinate. When these positions are compared with their counterparts in the FK5 catalog, systematic errors in the FK5 are found that vary in both right ascension and declination and can be as large as 100 mas in magnitude. No magnitude-dependent errors in the FK5 were found. Moreover, the true error in FK5 star positions is determined to be ~+/-80mas in both coordinates or two times the expected catalog positional errors. There is an excellent agreement between the systematic errors in the FK5 found in this paper and those presented in Lindegren et al. (1995A&A...304...44L) comparing FK5 and Hipparcos 30-month star positions. By comparing corresponding FASTT and FK5 star positions, the link between the optical and extragalactic reference frames was determined and is given by the following rotations ({omega}_x_,{omega}_y_,{omega}_z_) = (3+/-5, 25+/-5, 16+/-4) (s.e.) mas, which agree well with previous determinations made by other investigators. Two of the rotations ({omega}_y_,{omega}_z_) are significantly larger than their standard errors and, therefore, presumably real. Finally, since these rotations are small (<=25mas), the FK5 and extragalactic reference frames must be closely aligned to one another.
152. Extended Hipparcos Compilation (XHIP)
ID:
ivo://CDS.VizieR/V/137D
Title:
Extended Hipparcos Compilation (XHIP)
Short Name:
V/137D
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Extended Hipparcos Compilation (XHIP) cross-references the New Hipparcos Reduction (HIP2, Cat. I/311) with relatable data from a broad survey of presently available sources. The resulting collection uniquely assigns 116,096 spectral classifications, 46,392 radial velocities, and 19,097 iron abundances [Fe/H] to Hipparcos stars. Stellar classifications from SIMBAD and indications of multiplicity from either CCDM (Cat. I/274) or WDS (Cat. B/wds) are provided. Parameters for solar encounters and Galactic orbits are calculated for a subset of stars that can be made kinematically complete. Memberships in open clusters and stellar associations are assigned. We also provide stellar ages from The Geneva-Copenhagen survey of the Solar neighbourhood III (Cat. V/130), identifications of exoplanet host stars, and supplemental photometry from 2MASS (Cat. II/246) and SIMBAD.
153. Extended Meingast 1 source catalogue
ID:
ivo://CDS.VizieR/J/A+A/639/A64
Title:
Extended Meingast 1 source catalogue
Short Name:
J/A+A/639/A64
Date:
21 Oct 2021
Publisher:
CDS
Description:
Nearby stellar streams carry unique information on the dynamical evolution and disruption of stellar systems in the Galaxy, the mass distribution in the disk, and they provide unique targets for planet formation and evolution studies. Recently, Meingast 1, a 120{deg} stellar stream with a length of at least 400pc, was discovered. We aim to revisit the Meingast 1 stream to search for new members within its currently known 400pc extent, using Gaia DR2 data and an innovative machine learning approach. We used a bagging classifier of one-class support vector machines with Gaia DR2 data to perform a 5D search (positions and proper motions) for new stream members. The ensemble was created by randomly sampling 2.4 million hyper-parameter realizations admitting classifiers that fulfill a set of prior assumptions. We used the variable prediction frequency resulting from the multitude of classifiers to estimate a stream membership criterion, which we used to select high-fidelity sources. We used the HR diagram and the Cartesian velocity distribution as test and validation tools. We find about 2000 stream members with high fidelity, or about an order of magnitude more than previously known, unveiling the stream's population across the entire stellar mass spectrum, from B stars to M stars, including white dwarfs. We find that, apart from being slightly more metal poor, the HRD of the stream is indistinguishable from that of the Pleiades cluster. For the mass range at which we are mostly complete, ~0.2M_{sun}_<M<~4M_{sun}_, we find a normal IMF, allowing us to estimate the total mass of stream to be about 2000M_{sun}_, making this relatively young stream by far the most massive one known. In addition, we identify several white dwarfs as potential stream members. The nearby Meingast 1 stream, due to its richness, age, and distance, is a new fundamental laboratory for star and planet formation and evolution studies for the poorly studied and gravitationally unbound star formation mode. We also demonstrate that one-class support vector machines can be effectively used to unveil the full stellar populations of nearby stellar systems with Gaia data.
154. Extension of ICRF for selected areas down to V=16
ID:
ivo://CDS.VizieR/J/A+A/409/361
Title:
Extension of ICRF for selected areas down to V=16
Short Name:
J/A+A/409/361
Date:
21 Oct 2021
Publisher:
CDS
Description:
A catalogue of accurate positions and proper motions for 678,828 objects is provided. Objects are within areas of special astronomical interest, containing extragalactic radio sources, mostly from ICRF (see Cat. <I/251>), and pre-main-sequence (PMS) stars in Southern star-forming regions (Chamaeleon, Lupus and Upper Scorpius-Ophiuchus). This work represents a major upgrade of that presented in Camargo et al., 2001, Cat. <J/A+A/375/308>, aiming at the extension of the ICRF at optical wavelengths in regions of special astronomical interest, using observations from the Bordeaux and Valinhos meridian circles. Along with the new fields, the main differences, when compared to the first release, are: a much larger sky coverage, the replacement of the AC2000 by its upgraded version AC2000.2 (<I/275>) as one of the first epoch astrometrical sources, inclusion of Tycho-2 (<I/259>) and 2MASS (2nd Incremental Data Release, See Cat <II/246>) photometry when available, and the correction for a magnitude equation on the Valinhos right ascension system as well. Positional external precisions, on both coordinates, range from 50-60mas (V<=13.5) to 70-140mas (13.5<V<=16.0). For the proper motions, precisions range from 3mas/year to about 15mas/year, depending on magnitude and declination. The strips scanned by the meridian circles are described in Table 1
155. Extension of ICRF for selected areas down to V=15
ID:
ivo://CDS.VizieR/J/A+A/375/308
Title:
Extension of ICRF for selected areas down to V=15
Short Name:
J/A+A/375/308
Date:
21 Oct 2021
Publisher:
CDS
Description:
A catalogue of accurate positions and proper motions for 41,721 objects is provided. Objects are within areas of special astronomical interest, containing extragalactic radio sources, mostly from ICRF (see Cat. I/251), and pre-main-sequence (PMS) stars in Southern star-forming regions (Chamaeleon, Lupus and Upper Scorpius-Ophiuchus). Positions and proper motions were derived by combining current epoch positions, obtained with the Valinhos CCD meridian circle (VMC, see 1999A&AS..134..173V), with first epoch catalogues, AC2000 (I/247) and USNO-A2.0 (I/252) mainly, as well as positions from plate measurements performed with the MAMA measuring machine (Guibert J., Charvin P. & Stoclet P., 1983, in Proceedings of the 78th Colloquium of the IAU), in Paris. On average, objects with V<=14.0 have positional precisions better than 50mas in both coordinates, and 100mas near the detection limit of the VMC (V~16,0). For proper motions, average precisions are better than 4mas/year, whatever the magnitude, when delta>=-17{deg}. To the south of this declination, a magnitude dependence is verified due to a particular feature of the USNO-A2.0's epochs, providing figures of 3mas/year when V<=12.0, where the participation of AC2000 is noted, and reaching 17mas/year at the detection limit. The catalogue data is grouped by area, following the same order and identification as given in table 2 of the paper; within each area, objects are sorted by right ascension. The respective record numbers for the beginning of each area are provided in a separate table.
156. Extragalactic radio sources optical positions
ID:
ivo://CDS.VizieR/J/A+AS/120/201
Title:
Extragalactic radio sources optical positions
Short Name:
J/A+AS/120/201
Date:
21 Oct 2021
Publisher:
CDS
Description:
Based on 28 individual catalogues, in which the positions of optical counterparts of extragalactic radio sources are listed, we compiled a combined catalogue by means of a weighted least squares adjustment. The catalogue is in the system of FK5/J2000.0. It consists of about five hundred sources, among which there are 56 primary sources with position uncertainties as 0.09". Comparisons show that the orientation differences between optical and radio frames are A1=-0.013"+/-0.012", A2=0.077"+/-0.012", A3=0.005"+/-0.009". Local relative deformations are not obvious within the precision of ground-based optical observations.
157. Extragalactic Reference Link Catalog (ERLcat)
ID:
ivo://CDS.VizieR/I/273A
Title:
Extragalactic Reference Link Catalog (ERLcat)
Short Name:
I/273A
Date:
21 Oct 2021
Publisher:
CDS
Description:
This is an astrometric catalog, providing positions of 89,422 stars in 398 selected fields of extragalactic reference frame sources. The stars are mainly in the 11 to 14 magnitude range. The average positional accuracy is about 50 mas per coordinate at the epoch of observation, which is between 1976.2 and 1991.9. The observations are based on photographic plates, taken with 2 telescopes which are: - the Hamburg Zone astrograph (in the Northern Hemisphere) - the USNO Twin astrograph at Black Birch (New Zealand)
158. Far-UV photometry in Ori
ID:
ivo://CDS.VizieR/J/ApJS/89/259
Title:
Far-UV photometry in Ori
Short Name:
J/ApJS/89/259
Date:
21 Oct 2021
Publisher:
CDS
Description:
(no description available)
159. FBS blue stellar objects DSS1/DSS2 astrometry
ID:
ivo://CDS.VizieR/J/A+A/426/367
Title:
FBS blue stellar objects DSS1/DSS2 astrometry
Short Name:
J/A+A/426/367
Date:
21 Oct 2021
Publisher:
CDS
Description:
Accurate measurements of the positions of 1103 First Byurakan Survey (FBS) blue stellar objects (the Second part of the FBS, <II/223>) have been carried out on the DSS1 and DSS2 (red and blue images). To establish the accuracy of the DSS1 and DSS2, measurements have been made for 153 AGN for which absolute VLBI coordinates have been published. The rms errors are: 0.45" for DSS1, 0.33" for DSS2 red, and 0.59" for DSS2 blue in each coordinate, the corresponding total positional errors being 0.64", 0.46", and 0.83", respectively. The highest accuracy (0.42") is obtained by weighted averaging of the DSS1 and DSS2 red positions. It is shown that by using all three DSS images accidental errors can be significantly reduced. The comparison of DSS2 and DSS1 images made it possible to reveal positional differences and proper motions for 78 objects (for 62 of these for the first time), including new high-probability candidate white dwarfs, and to find objects showing strong variability, i.e. high-probability candidate cataclysmic variables.
160. Field horizontal-branch stars in the Galaxy
ID:
ivo://CDS.VizieR/J/A+A/431/143
Title:
Field horizontal-branch stars in the Galaxy
Short Name:
J/A+A/431/143
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a sample of 8321 candidate Field Horizontal-Branch (FHB) stars selected by automatic spectral classification in the digital data base of the Hamburg/ESO objective-prism survey. The stars are distributed over 8225 square degrees of the southern sky, at |b|>~30{deg}. The average distance of the sample, assuming that they are all FHB stars, is 9.8kpc, and distances of up to ~30kpc are reached. Moderate-resolution spectroscopic follow-up observations and $UBV$ photometry of 125 test sample stars demonstrate that the contamination of the full candidate sample with main-sequence A-type stars is <16%, while it would be up to 50% in a flux-limited sample at high galactic latitudes. Hence more than ~6800 of our FHB candidates are expected to be genuine FHB stars. The candidates are being used as distance probes for high-velocity clouds and for studies of the structure and kinematics of the Galactic halo.

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