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11. Southern stars of high radial velocity
ID:
ivo://CDS.VizieR/J/AJ/89/1897
Title:
Southern stars of high radial velocity
Short Name:
J/AJ/89/1897
Date:
21 Oct 2021
Publisher:
CDS
Description:
Slit spectra have been obtained for 82 stars for which the objective-prism radial-velocity catalogue of Stock lists velocities over 130km/s in magnitude. The slit spectra reveal that many of these objects are F-K stars of low metal abundance, including some stars apparently as metal weak as any presently known. Radial velocities were derived from the slit spectra to examine the reliability of the large objective-prism velocities. The slit results confirm that the majority of the stars are indeed of high velocity, but show that the objective-prism technique tends to produce velocities systematically too large in magnitude by about 40km/s. It was also found that a large objective-prism velocity that is of low weight or from spectra near a plate edge is likely spurious. A search of the 10000 entries in Stock's catalogue yields 205 objects with radial-velocity magnitudes over 130km/s. Sixty-three of these velocities are not suspect because of low weight or edge proximity. An additional 14 stars of lower quality prism velocities were confirmed to have high velocities from the slit spectra. The high-velocity stars appear to form two distinct groups: metal-weak F-K stars and spectroscopically normal main-sequence A stars. Slit spectra were obtained on six nights in April 1978 utilizing the Boller and Chivens spectrograph and the Carnegie image tube at the Cassegrain focus of the 1-m Yale telescope at CTIO.
12. Spectroscopically Selected Halo K Giants
ID:
ivo://CDS.VizieR/V/65
Title:
Spectroscopically Selected Halo K Giants
Short Name:
V/65
Date:
21 Oct 2021
Publisher:
CDS
Description:
The catalog results from a survey for distant Field K giants in the Galactic halo made for purposes of locating a chemically and kinematically unbiased sample out to about 25 kpc from the Sun. The motivation for the study and sample selection are outlined by Ratnatunga & Freeman (1985ApJ...291..260R), while details and analysis of the results will be found in Ratnatunga & Freeman (1989). Three high-galactic latitude fields each of 20 square degrees, designated by their Selected-Area identifications, include the following: SA 141 (l=240,b=-85); SA 189 (277, -50); and SA 127 (272, +38), and have the apparent magnitude range 13 < V < 16 and color range (B-V) > 0.9. Stars were selected from PDS photographic photometry of Schmidt plates (see Ratnatunga 1983, catalog II/121). K-giant selection used the Mgb+MgH feature at 5100A from digital image analysis of PDS scans of ESO 1-m Schmidt telescope objective-prism spectra with 450 A/mm at H-gamma resolution on IIIa-J plates exposed through a Schott GG475 filter. Luminosity confirmation, line-of-sight velocities, and metallicity were determined from 2-A resolution slit spectra taken with the 4-m Anglo- Australian and 1.9-m Mount Stromlo telescopes. Cross identifications exist for some stars in the SA 141 SGP field only.
13. UBVRI photometry of NLTT stars
ID:
ivo://CDS.VizieR/J/AJ/98/1693
Title:
UBVRI photometry of NLTT stars
Short Name:
J/AJ/98/1693
Date:
21 Oct 2021
Publisher:
CDS
Description:
UBVRI photometry is presented for a sample of 1656 southern stars, including 1211, that were previously not measured, drawn from the NLTT (Luyten, 1979; catalogue I/98) proper-motion catalog; the catalog is shown to be a rich source of subdwarfs. The normalized UV excess, d(U-B)0.6, photometric parallax, and interstellar reddening are calculated for each star when possible. Residuals between the photometry and the magnitudes published in the NLTT catalog indicate that the latter have a large scatter (~0.6mag) and therefore the values tabulated in the NLTT catalog must be regarded as approximate only. The erratum (Astron. J. 99, 1336) which deals with position angles of proper motions (pmPA) has been taken into account.
14. uvby-beta photometry of metal-poor stars
ID:
ivo://CDS.VizieR/II/180
Title:
uvby-beta photometry of metal-poor stars
Short Name:
II/180
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using the calibrations derived by Schuster and Nissen (=1989A&A...221...65S), the interstellar color excesses, E(b-y), and the metallicities, [Fe/H], have been determined for the 711 high velocity and metal-poor stars in the catalogue of uvby-beta photometry (=1988A&AS...73..225S). 220 of these listed in table1 turn out to be halo stars according to the criterion [Fe/H] <= -1.0. About 15% of the halo stars have colors that are significantly affected by interstellar reddening, i.e. E(b-y) > 0.025. The distributions in the c0-(b-y)0 diagram of the halo stars grouped according to [Fe/H], have well defined turn-off points. From the Teff values of these points a minimum age of 18-20 Gyr for the halo stars is determined. However, this age may be 2-3 Gyr too high due to a possible systematic error in Teff for the stellar models used. Relative ages of 77 halo stars in the turn-off region of the c0-(b-y)0 diagram are derived using the isochrones VandenBerg and Bell (=1985ApJS...58..561V). Assuming that the O/Fe abundance ratio is constant in halo stars, evidence of a cosmic age scatter of +/-2.5Gyr at a given metallicity is found. Furthermore, the mean age of the halo stars is found to decrease smoothly by about 3 Gyr from [Fe/H]= -2.0 to -1.0. These results suggest that a pressure-supported slow uniform collapse controlled the formation and early evolution of the Galaxy. However, the scenario of Searle and Zinn (=1978ApJ...225..357S) is also compatible with the results.

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