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211. Hipparcos, the New Reduction
ID:
ivo://CDS.VizieR/I/311
Title:
Hipparcos, the New Reduction
Short Name:
I/311
Date:
21 Oct 2021
Publisher:
CDS
Description:
A new reduction of the astrometric data as produced by the Hipparcos mission has been published, claiming accuracies for nearly all stars brighter than magnitude Hp=8 to be better, by up to a factor 4, than in the original catalogue. The new Hipparcos astrometric catalogue is checked for the quality of the data and the consistency of the formal errors as well as the possible presence of error correlations. The differences with the earlier publication are explained. Methods. The internal errors are followed through the reduction process, and the external errors are investigated on the basis of a comparison with radio observations of a small selection of stars, and the distribution of negative parallaxes. Error correlation levels are investigated and the reduction by more than a factor 10 as obtained in the new catalogue is explained. Results. The formal errors on the parallaxes for the new catalogue are confirmed. The presence of a small amount of additional noise, though unlikely, cannot be ruled out. Conclusions. The new reduction of the Hipparcos astrometric data provides an improvement by a factor 2.2 in the total weight compared to the catalogue published in 1997, and provides much improved data for a wide range of studies on stellar luminosities and local galactic kinematics.
212. HIP stars DEC proper motions comparison
ID:
ivo://CDS.VizieR/J/A+A/631/A145
Title:
HIP stars DEC proper motions comparison
Short Name:
J/A+A/631/A145
Date:
21 Oct 2021
Publisher:
CDS
Description:
The second solution of the Gaia catalog, which has been available since April 2018, plays an important role in the realization of the future Gaia reference frame. Since 1997, the reference frame has been materialized by the optical HIPPARCOS positions of about 120000 stars. The HIPPARCOS has been compared with and linked to the International Celestial Reference Frame (ICRF). The ICRF is materialized by means of the radio positions of extragalactic sources using very large baseline interferometry observations. Both, the HIPPARCOS and Gaia missions belong to the European Space Agency, and it is important to note that the Gaia catalog is going to replace the HIPPARCOS catalog. It has been shown that the International Latitude Service zenith telescope data pertaining to ground-based surveys that span a time baseline of about 80yr, and which are also key when measuring proper motions, could be useful for the accurate determination of {mu}_{delta}_ for 387 ILS stars. Therefore, in this study we aim first to reduce these stars to the HIPPARCOS reference system; second, to made our original catalog of {mu}_{delta}_, which we refer to as the ILS catalog, for these 387 bright stars; third, to present comparison results of the four catalogs by pairs (the ILS, HIPPARCOS or HIP, new HIPPARCOS or NHIP, and Gaia DR2); and fourth, to analyze the differences in {mu}_{delta}_ between pairs of catalogs to characterize the {mu}_{delta}_ errors for these catalogs with a special focus on the Gaia DR2 and ILS catalogs. At seven ILS sites around the world at latitude 39.1{deg}, a set of seven telescopes was used to monitor the latitude variation via observations of the same stars for about 80 yr. Here, the inverse task was applied to improve {mu}_{delta}_ values of the 387 HIPPARCOS stars using the previously mentioned observations. Due to the specific Horrebow-Talcott method of the measured star pair, it is difficult to determine {mu}_{delta}_ for each single star. However, we achieved this by developing the original method and in combination with the HIPPARCOS data. We used the previously developed least squares method and formula to determine the coefficients, which describe the systematic part of differences in {mu}_{delta}_ between the pairs of catalogs. We calculated the coefficients with the aforementioned formula (in line with the coordinates, stellar magnitude, and color index of every star) to compare ILS, HIP, NHIP, and Gaia DR2 data of {mu}_{delta}_ against each other by using the set of 387 stars. The presented differences of {mu}_{delta}_ show that the systematic errors in the four catalogs are nearly at the same level of 0.1mas/yr. This means that the DR2 and ILS {mu}_{delta}_ values are in good agreement with each other, and with values from the HIPPARCOS and new HIPPARCOS catalogs. Also, the random errors of differences are small ones; they are near 1mas/yr for ILS-HIP and ILS-NHIP, and about 2mas/yr for ILS-DR2, HIP-DR2, and NHIP-DR2. It is important to note that there is a similar level of proper motion formal errors in HIPPARCOS and new HIPPARCOS catalogs.
213. HITEP. II. Transiting exoplanets imaging
ID:
ivo://CDS.VizieR/J/A+A/610/A20
Title:
HITEP. II. Transiting exoplanets imaging
Short Name:
J/A+A/610/A20
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of the second part of a high resolution imaging survey of hot Jupiter host stars. We search for binary companions to known transiting exoplanet host stars, in order to determine the multiplicity properties of hot Jupiter host stars. We also search for and characterise unassociated stars along the line of sight, allowing photometric and spectroscopic observations of the planetary system to be corrected for contaminating light.
214. HKE Sydney Catalog
ID:
ivo://CDS.VizieR/I/73
Title:
HKE Sydney Catalog
Short Name:
I/73
Date:
21 Oct 2021
Publisher:
CDS
Description:
The methods for constructing a catalogue of 20457 star positions for the epoch 1964 between -48 and -58{deg} declination are described. The positions were obtained by the overlap method, and images generated by a coarse diffraction grating were employed to control magnitude-related effects on the position. A selection of about 2 faint Astrographic Catalog (AC) stars per square degree was included to serve as material for the eventual determination of magnitude effects on the AC positions. The standard error of a catalogued position estimate based on 2 images is 0.12'' in either coordinate.
215. HK survey emission-line candidates
ID:
ivo://CDS.VizieR/J/AJ/112/1188
Title:
HK survey emission-line candidates
Short Name:
J/AJ/112/1188
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a list of 218 additional candidate emission-line objects discovered with the northern and southern HK interference-filter/ objective-prism survey of Beers and collaborators. The objects have apparent magnitudes in the range 10<=B<=16, several magnitudes fainter than obtained with previous prism surveys of similar resolution. Of the new candidates, 73 have been previously identified. The total list of HK-survey emission-line candidates now numbers 376 objects, 104 of which were noted by previous surveys.
216. Hot Stuff for One Year (HSOY)
ID:
ivo://CDS.VizieR/I/339
Title:
Hot Stuff for One Year (HSOY)
Short Name:
I/339
Date:
21 Oct 2021
Publisher:
CDS
Description:
Recently, the first installment of data from ESA's Gaia astrometric satellite mission (Gaia DR1) was released, containing positions of more than 1 billion stars with unprecedented precision, as well as proper motions and parallaxes, however only for a subset of 2 million objects. The second release will include those quantities for most objects. In order to provide a dataset that bridges the time gap between the Gaia DR1 and Gaia DR2 releases and partly remedies the lack of proper motions in the former, HSOY ("Hot Stuff for One Year") was created as a hybrid catalog between Gaia and ground-based astrometry, featuring proper motions (but no parallaxes) for a large fraction of the DR1 objects. While not attempting to compete with future Gaia releases in terms of data quality or number of objects, the aim of HSOY is to provide improved proper motions partly based on Gaia data, allowing studies to be carried out just now or as pilot studies for later projects requiring higher-precision data. The HSOY catalog was compiled using the positions taken from Gaia DR1 combined with the input data from the PPMXL catalog, employing the same weighted least-squares technique that was used to assemble the PPMXL catalog itself. This effect resulted in a four-parameter astrometric catalog containing 583 million stars, with Gaia DR1 quality positions and proper motions with precisions from far less than 1 mas/yr to 5 mas/yr, depending on object brightness and location on the sky.
217. HST astrometry of TNOs
ID:
ivo://CDS.VizieR/J/ApJS/189/336
Title:
HST astrometry of TNOs
Short Name:
J/ApJS/189/336
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present 1428 individual astrometric measurements of 256 trans-Neptunian objects made with Hubble Space Telescope (HST). The observations were collected over three years with two instruments, the Wide Field Planetary Camera 2 and the Advanced Camera for Surveys High Resolution Camera, as part of four HST programs. We briefly describe the data and our analysis procedures. The submission of these measurements to the Minor Planet Center increased the individual arc length of objects by 1.83 days to 8.11 years. Of the 256 total objects, 62 (24.2%) had arc length increases of >=3 years. The arc length for 60 objects (23.4%) was increased by a factor of 2 or greater.
218. HST FGS-1r parallaxes for 8 metal-poor stars
ID:
ivo://CDS.VizieR/J/ApJ/835/152
Title:
HST FGS-1r parallaxes for 8 metal-poor stars
Short Name:
J/ApJ/835/152
Date:
21 Oct 2021
Publisher:
CDS
Description:
Hubble Space Telescope (HST) fine guidance sensor observations were used to obtain parallaxes of eight metal-poor ([Fe/H]< -1.4) stars. The parallaxes of these stars determined by the new Hipparcos reduction average 17% accuracy, in contrast to our new HST parallaxes, which average 1% accuracy and have errors on the individual parallaxes ranging from 85 to 144{mu}as. These parallax data were combined with HST Advanced Camera for Surveys photometry in the F606W and F814W filters to obtain the absolute magnitudes of the stars with an accuracy of 0.02-0.03 mag. Six of these stars are on the main sequence (MS) (with -2.7<[Fe/H]< -1.8) and are suitable for testing metal-poor stellar evolution models and determining the distances to metal-poor globular clusters (GCs). Using the abundances obtained by O'Malley+ (2017ApJ...838...90O), we find that standard stellar models using the VandenBerg & Clem (2003AJ....126..778V) color transformation do a reasonable job of matching five of the MS stars, with HD 54639 ([Fe/H]=-2.5) being anomalous in its location in the color-magnitude diagram. Stellar models and isochrones were generated using a Monte Carlo analysis to take into account uncertainties in the models. Isochrones that fit the parallax stars were used to determine the distances and ages of nine GCs (with -2.4{<=}[Fe/H]{<=}-1.9). Averaging together the age of all nine clusters led to an absolute age of the oldest, most metal-poor GCs of 12.7+/-1.0Gyr, where the quoted uncertainty takes into account the known uncertainties in the stellar models and isochrones, along with the uncertainty in the distance and reddening of the clusters.
219. Hyades tidal tails with Gaia DR2
ID:
ivo://CDS.VizieR/J/A+A/621/L3
Title:
Hyades tidal tails with Gaia DR2
Short Name:
J/A+A/621/L3
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the discovery of two well-defined tidal tails emerging from the Hyades star cluster. The tails were detected in Gaia DR2 data by selecting cluster members in the 3D galactocentric cylindrical velocity space. The robustness of our member selection is reinforced by the fact that the sources depict an almost noiseless, coeval stellar main sequence in the observational Hertzsprung-Russel diagram. The spatial arrangement of the selected members represents a highly flattened shape with respect to the direction of movement along the clusters' orbit in the Galaxy. The size of the entire structure, within the limits of the observations, measures about 200pc in its largest extent, while being only about 25pc thick. This translates into an on-sky extent of well beyond 100deg. Intriguingly, a top-down view on the spatial distribution reveals a distinct S-shape, reminiscent of tidal tails that have been observed for globular clusters and also of tails that were modeled for star clusters bound to the Galactic disk. Even more remarkable, the spatial arrangement as well as the velocity dispersion of our source selection is in excellent agreement with previously published theoretical predictions for the tidal tails of the Hyades. An investigation into observed signatures of equipartition of kinetic energy, that is, mass segregation, remains unsuccessful, most likely because of the sensitivity limit for radial velocity measurements with Gaia.
220. IC 4665
ID:
ivo://CDS.VizieR/J/AJ/105/1441
Title:
IC 4665
Short Name:
J/AJ/105/1441
Date:
21 Oct 2021
Publisher:
CDS
Description:
The results of a combined astrometric, photometric, and spectroscopic program to identify members of the open cluster IC 4665 are presented. Numerous new proper motion/photometric candidate members and at least 23 M dwarfs with H-alpha emission have been identified. A reanalysis of IC 4665's age using different methods yields conflicting results ranging from approx. 3x10^7^ yr to the age of the Pleiades. This study provides a list of candidate cluster members in the intermediate and low-mass regime of this cluster. Future spectroscopic observations of these candidates should eventually identify true cluster members. The results of new echelle observations of some candidates and the photometric monitoring of one apparent cluster member are given in an appendix.

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