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Title:
The A0 stars [ Erratum: 1984ApJS...56..650E ]
Authors:
Eggen, O. J.
Affiliation:
AA(Observatorio Interamericano de Cerro Tololo, La Serena, Chile)
Publication:
Astrophysical Journal Supplement Series (ISSN 0067-0049), vol. 55, Aug. 1984, p. 597-632. (ApJS Homepage)
Publication Date:
08/1984
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
A Stars, B Stars, Dwarf Stars, Peculiar Stars, Star Clusters, Stellar Luminosity, Astrometry, Binary Stars, Giant Stars, Interstellar Extinction, Radial Velocity, Spectrum Analysis, Stellar Evolution, Stellar Models, Stellar Spectrophotometry
DOI:
10.1086/190971
Bibliographic Code:
1984ApJS...55..597E

Abstract

A photometric grid, standardized on MK spectral standards, has been used to compare spectral types and luminosity classes obtained photometrically with those in two extensive spectral surveys covering the entire sky. Major discrepancies include the spectroscopic classification of B9.5, which may indicate an otherwise unrecognized spectral peculiarity, a different A0/A1 spectral type boundary in the two samples involved, the well-known misclassification of weak helium stars, and an appreciable percentage of stars which are called dwarfs spectroscopically but are of higher photometric luminosity. The space motion vectors of these stars for which radial velocities are available, and excluding the minimum of 25 percent that are spectroscopic binaries without orbital elements, show structure in their distribution in the (U, V)-plane, with members of the Local Association and the Hyades and Sirius superclusters forming obvious concentrations. The members of the Local Association in the samples are mainly old (more than 200 million years) mode A stars, although a few much younger stars are included. The members of the Hyades and Sirius superclusters contain many blue stragglers, including several peculiar stars of the Hg, Mn, and Si varieties.

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