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31. Combined astrometric catalogue EOC-3
ID:
ivo://CDS.VizieR/J/A+A/463/783
Title:
Combined astrometric catalogue EOC-3
Short Name:
J/A+A/463/783
Date:
21 Oct 2021
Publisher:
CDS
Description:
In the past, we collected the astrometric observations of latitude/universal time variations made worldwide at 33 observatories. These observations, referred to Hipparcos Catalogue, were then used to determine the Earth Orientation Parameters (EOP) at 5-day intervals, covering the interval 1899.7-1992.0. Later on, new astrometric catalogues (such as ARHIP or TYCHO-2) appeared as combination of Hipparcos/Tycho positions with ground-based catalogues. These catalogues yield more accurate proper motions than the original Hipparcos Catalogue. Many of the objects observed in the programmes of monitoring Earth orientation from the ground are double or multiple systems, having non-negligible periodic motions. We aim at obtaining a star catalogue with improved proper motions and quasi-periodic terms reflecting orbital motions of the stars observed in these programmes. We used about 4.5 million observations of latitude/universal time variations, and combined them with the catalogues ARIHIP, TYCHO-2 etc... in order to obtain Earth Orientation Catalogue (EOC). Spectral analysis of ground-based data is made in order to discover which of the observed objects display periodic motions, and the method of least squares is then used to estimate corresponding amplitudes and phases. The third version of the catalogue, EOC-3, contains 4418 different objects (i.e., stars, components of double stars, photocenters). Our attempt leads to a description of more accurate paths of the observed objects that will be eventually used for another determination of the Earth Orientation Parameters in the twentieth century.
32. Cool stars chromospheric activity catalog
ID:
ivo://CDS.VizieR/J/A+A/616/A108
Title:
Cool stars chromospheric activity catalog
Short Name:
J/A+A/616/A108
Date:
21 Oct 2021
Publisher:
CDS
Description:
Chromospheric activity monitoring of a wide range of cool stars can provide valuable information on stellar magnetic activity and its dependence on fundamental stellar parameters such as effective temperature and rotation. We compile a chromospheric activity catalogue of 4454 cool stars from a combination of archival HARPS spectra and multiple other surveys, including the Mount Wilson data that have recently been released by the NSO. We explore the variation in chromospheric activity of cool stars along the main sequence for stars with different effective temperatures. Additionally, we also perform an activity-cycle period search and investigate its relation with rotation. The chromospheric activity index, S-index, was measured for 304 main-sequence stars from archived high-resolution HARPS spectra. Additionally, the measured and archived S-indices were converted into the chromospheric flux ratio logR'HK. The activity-cycle periods were determined using the generalised Lomb-Scargle periodogram to study the active and inactive branches on the rotation-activity-cycle period plane. The global sample shows that the bimodality of chromospheric activity, known as the Vaughan-Preston gap, is not prominent, with a significant percentage of the stars at an intermediate-activity level around logR'HK=-4.75. Independently, the cycle period search shows that stars can lie in the region intermediate between the active and inactive branch, which means that the active branch is not as clearly distinct as previously thought. The weakening of the Vaughan-Preston gap indicates that cool stars spin down from a higher activity level and settle at a lower activity level without a sudden break at intermediate activity. Some cycle periods are close to the solar value between the active and inactive branch, which suggests that the solar dynamo is most likely a common case of the stellar dynamo.
33. Cordoba Durchmusterung
ID:
ivo://CDS.VizieR/I/114
Title:
Cordoba Durchmusterung
Short Name:
I/114
Date:
21 Oct 2021
Publisher:
CDS
Description:
The "Cordoba Durchmusterung" (CD, Thome 1892-1932) is a visual survey of southern stars in the declination zones -22 to -89 deg, carried out as an extension to the "Bonner Durchmusterung" (BD) catalogs of Argelander (1859-1862) (see also Kuestner 1903) and Schoenfeld (1886). It contains 613959 records for stars brighter than 10.0 magnitude.
35. Earth Orientation Catalog 4 (EOC-4)
ID:
ivo://CDS.VizieR/J/A+A/509/A3
Title:
Earth Orientation Catalog 4 (EOC-4)
Short Name:
J/A+A/509/A3
Date:
21 Oct 2021
Publisher:
CDS
Description:
The astrometric ground-based observations of latitude / universal time variations, covering the interval 1899.7-2003.0, were used in combination with Hipparcos / Tycho positions and some older ground-based catalogs to construct a family of catalogs, tailored for long-term Earth rotation studies. These catalogs, called Earth Orientation Catalogs (EOC-1 through EOC-3) yielded more accurate proper motions than the original Hipparcos Catalogue, and its latest version, EOC-3, even periodic motions for a large portion of the stars. About 4.5 million observations made at 33 observatories are combined with the catalogs ARIHIP, TYCHO-2 etc... in order to obtain EOC-4. Spectral analysis of ground-based data and comparison with the USNO Sixth Catalog of Orbits of Visual Binary Stars are used to discover which of the observed objects display periodic motions, and improved combination procedures are used. The catalog contains 4418 different objects (i.e., stars, components of double stars, photocenters), out of which 599 have significant orbital motions.
36. 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.
37. EUV estimates from CaII H&K activity
ID:
ivo://CDS.VizieR/J/A+A/644/A67
Title:
EUV estimates from CaII H&K activity
Short Name:
J/A+A/644/A67
Date:
21 Oct 2021
Publisher:
CDS
Description:
Atmospheric escape is an important factor shaping the exoplanet population and hence drives our understanding of planet formation. Atmospheric escape from giant planets is driven primarily by the stellar X-ray and extreme- ultraviolet (EUV) radiation. Furthermore, EUV and longer wavelength UV radiation power disequilibrium chemistry in the middle and upper atmosphere. Our understanding of atmospheric escape and chemistry, therefore, depends on our knowledge of the stellar UV fluxes. While the far-ultraviolet fluxes can be observed for some stars, most of the EUV range is unobservable due to the lack of a space telescope with EUV capabilities and, for the more distant stars, to interstellar medium absorption. Thus, it becomes essential to have indirect means for inferring EUV fluxes from features observable at other wavelengths. We present here analytic functions for predicting the EUV emission of F, G, K, and M-type stars from the log R'HK activity parameter that is commonly obtained from ground-based optical observations of the Ca II H&K lines. The scaling relations are based on a collection of about 100 nearby stars with published log R'HK and EUV flux values, where the latter are either direct measurements or inferences from high-quality far-ultraviolet (FUV) spectra. The scaling relations presented here return EUV flux values with an accuracy of about three, which is slightly lower than that of other similar methods based on FUV or X-ray measurements.
38. Exoplanet hosts/field stars age consistency
ID:
ivo://CDS.VizieR/J/A+A/585/A5
Title:
Exoplanet hosts/field stars age consistency
Short Name:
J/A+A/585/A5
Date:
21 Oct 2021
Publisher:
CDS
Description:
Transiting planets around stars are discovered mostly through photometric surveys. Unlike radial velocity surveys, photometric surveys do not tend to target slow rotators, inactive or metal-rich stars. Nevertheless, we suspect that observational biases could also impact transiting-planet hosts. This paper aims to evaluate how selection effects reflect on the evolutionary stage of both a limited sample of transiting-planet host stars (TPH) and a wider sample of planet-hosting stars detected through radial velocity analysis. Then, thanks to uniform derivation of stellar ages, a homogeneous comparison between exoplanet hosts and field star age distributions is developed. Stellar parameters have been computed through our custom-developed isochrone placement algorithm, according to Padova evolutionary models. The notable aspects of our algorithm include the treatment of element diffusion, activity checks in terms of logR'_HK_ and vsini, and the evaluation of the stellar evolutionary speed in the Hertzsprung-Russel diagram in order to better constrain age. Working with TPH, the observational stellar mean density {rho}_*_ allows us to compute stellar luminosity even if the distance is not available, by combining {rho}_* with the spectroscopic logg. The median value of the TPH ages is ~5Gyr. Even if this sample is not very large, however the result is very similar to what we found for the sample of spectroscopic hosts, whose modal and median values are [3, 3.5)Gyr and ~4.8Gyr, respectively. Thus, these stellar samples suffer almost the same selection effects. An analysis of MS stars of the solar neighbourhood belonging to the same spectral types bring to an age distribution similar to the previous ones and centered around solar age value. Therefore, the age of our Sun is consistent with the age distribution of solar neighbourhood stars with spectral types from late F to early K, regardless of whether they harbour planets or not. We considered the possibility that our selected samples are older than the average disc population.
39. 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)
40. Faintest stars
ID:
ivo://CDS.VizieR/J/ApJ/414/279
Title:
Faintest stars
Short Name:
J/ApJ/414/279
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present infrared K-band photometry of complete samples of VLM candidates constructed from IIIaF and IVN plates in 10 fields taken as part of the POSSII and UKSRC surveys. Using the I-K colors constructed for these stars we estimate a bolometric luminosity function which extends to MBol=13.75. We find significant evidence for a luminosity function decreasing toward these luminosities.

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