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Early type high-velocity stars in the solar neighborhood. IV - Four-color and H-beta photometry
Results are presented from photometric obaservations in the Stromgrenuvby four-color and H-beta systems of early-type high-velocity stars inthe solar neighborhood. Several types of photometrically peculiar starsare selected on the basis of their Stromgren indices and areprovisionally identified as peculiar A stars, field horizontal-branchstars, metal-poor stars near the Population II and old-disk turnoffs,metal-poor blue stragglers, or metallic-line A stars. Numerousphotometrically normal stars were also found.
| Speckle interferometry of HIPPARCOS link stars. III
A third list of stars is presented which have been tested by speckleinterferometry for use in the Hubble Space Telescope link between theHipparcos astrometric reference frame and the extragalactic VLBIreference frame. Structural information on angular scales of 0.15-1.2arcsec for 34 Southern Hemisphere stars is reported from observationsmade with the Imperial College Speckle Interferometer mounted on theMount Stromlo 1.9-m telescope. Twenty-four percent of the stars (8 outof the 34) show evidence of multiplicity, in agreement with previousobservations in this program.
| A catalogue of QSOs and link stars for the HST link of the HIPPARCOS reference frame
A list of bright (less than 17 mag) southern QSOs and bright (less than11 mag) stars that may be suitable for the Hubble Space Telescope linkbetween the Hipparcos astrometric reference frame and the VLBIextragalactic frame is presented. The QSOs have been selected fromvarious lists of radio objects and identifications. The stars have beenselected from the Strasbourg (CDS) data base and from the PreliminarySecond Cape Photographic Catalog, and supplemented with stars measuredfrom the SERC IIIa-J Schmidt survey. These QSOs and stars have beenincluded in the Hipparcos and HST schedule of observations.
| Early-type high-velocity stars in the solar neighborhood. II Photometry for 78 candidates
H-beta and four-color photometry are presented for 78 early-type,high-velocity star candidates consisting of: (1) 74 candidates listed ina previous paper; and (2) four candidates identified by Eggen (1970).All of the sample appears to be near the main sequence, with theexception of five of the AO-type stars that are probably on the fieldPopulation II horizontal branch. Almost one-third of the main-sequence Astars and nearly all of the F stars are seen as true high-velocityobjects, and several of the high-velocity F stars appear to have solarmetal abundances. The existence of young, metal-rich, high-velocitystars is supported by the data, and it is concluded that this populationmay contribute one A star to every thousand stars in the solarneighborhood.
| Early-type high-velocity stars in the solar neighborhood. I - List of candidates
Suspected nearby high-velocity stars of spectral types B and A areidentified by their proper motions, which are generally too small forthe stars to have been included in previous catalogs of high-velocitystars. The same selection process is then extended to spectral type Fstars, in order to both provide a companion sample and investigatewhether the hypothetical high-velocity, metal-rich population continuesto later spectral types. Of the presented list of 371 stars withconfirmed proper motions, 168 are of A and B spectral types. Photometricand spectroscopic observations of these stars are required to eliminatethose with misclassified spectra and convert proper motions into spacevelocities. The identification of type of stars is important forunderstanding apparent exceptions to the correlation between stellarages, metal abundances, and kinematic properties.
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