Which evolution for an AM star?
The behavior of calcium abundance is examined in relation to theevolutionary stage of some Am stars in three star clusters. It appearsthat, the more the Am star is evolved, the less is its calciumdeficiency. This observation makes it possible to suppose that DeltaDelphini stars and A-F giant stars photometrically similar to classicalAm stars could be descendants of the Am stars.
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Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.
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The occurrence of abnormal stars in open clusters
The age dependence of the frequencies of various types of abnormal starsin open clusters and associations is discussed. Spectra acquired atdispersions of 39 A/mm and 129 A/mm were used to determine the spectraltypes and luminosity classes of 661 stars in 14 open clusters andassociations. The frequencies of Ap(Si), Ap(Hg,Mn) and Ap(Sr,Cr) starsare found to increase with age to a level about that of field stars,while the rotational velocities of Ap(Si) and Ap(Hg,Mn) stars decreasewith time. Be stars in clusters exhibit a relatively constant frequency,roughly equal to that of Be field stars. The frequencies of stars withpronounced shell spectra are observed to remain constant with age, whilestars with unusually broad hydrogen lines (Vb stars) occur only in theyoungest clusters. The frequency of Am stars in clusters is notsignificantly different from that of field stars, and does not seem todepend on age, although rotational velocity is seen to decrease. It isconcluded that Ap or Am stars develop from stars of various rotationalspeeds, with a subsequent decrease in rotational velocity.
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A photometric study of the Orion OB 1 association. III - Subgroup analyses
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978ApJS...36..497W&db_key=AST
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Two sparse open clusters in the region of Collinder 132.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977PASP...89..803C&db_key=AST
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Spectral types in the ORI OB1 association.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977PASP...89..797A&db_key=AST
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A photometric study of the Orion OB 1 association. I - Observational data.
A catalog of observational data is presented for stars in the region ofthe young stellar association Orion OB 1. Photoelectric observationsobtained in the uvby-beta and UBV systems are compiled along withprevious photoelectric and spectroscopic data for all these stars aswell as for several bright members of the association with availablephotometric indices. Mean weighted values are computed for thephotometric data and summarized in tables expected to be reasonablycomplete for association members earlier than spectral type A0.Membership criteria are derived, and qualitative membershipprobabilities summarized, for the 526 stars in the final program. Theanalytical procedures are discussed for association stars of B,intermediate, and AF types. Effects of the nebular environment andvarious calibrations of Balmer-line and four-color indices areconsidered for the determination of absolute magnitudes for the B-typestars.
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Interstellar extinction in the Orion association
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968ApJ...152..913L&db_key=AST
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KURZE MITTEILUNG. Zur Expansion der Assoziation Cep III
Not Available
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Axial Rotation of Orion Stars of Spectral Type B5-B9.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1963ApJ...137..316M&db_key=AST
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Two-Dimensional Spectral Classification by Narrow-Band Photometry for B Stats in Clusters and Associations.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1958ApJ...128..185C&db_key=AST
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A Study of the Orion Aggregate of Early-Type Stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1952ApJ...116..251S&db_key=AST
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