Circular Polarization of Starlight
Of the 7500 stars cited in the Catalog of starlight polarization, thosewhich satisfy the condition P obs % and A V 0m.5 are selected. It ispresumed that the selected stars (n=216) have circularly polarizedlight.
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The Angular Momentum Evolution of 0.1-10 Msolar Stars from the Birth Line to the Main Sequence
Projected rotational velocities (vsini) have been measured for a sampleof 145 stars with masses between 0.4 and greater than 10Msolar (median mass 2.1 Msolar) located in theOrion star-forming complex. These measurements have been supplementedwith data from the literature for Orion stars with masses as low as 0.1Msolar. The primary finding from analysis of these data isthat the upper envelope of the observed values of angular momentum perunit mass (J/M) varies as M0.25 for stars on convectivetracks having masses in the range ~0.1 to ~3 Msolar. Thispower law extends smoothly into the domain of more massive stars (3-10Msolar), which in Orion are already on the zero-age mainsequence. This result stands in sharp contrast to the properties ofmain-sequence stars, which show a break in the power law and a sharpdecline in J/M with decreasing mass for stars with M<2Msolar. A second result of our study is that this break isseen already among the pre-main-sequence stars in our Orion sample thatare on radiative tracks, even though these stars are only a few millionyears old. A comparison of rotation rates seen for stars on either sideof the convective-radiative boundary shows that stars do not rotate assolid bodies during the transition from convective to radiative tracks.As a preliminary demonstration of how observations can be used toconstrain the processes that control early stellar angular momentum, weshow that the broad trends in the data can be accounted for by simplemodels that posit that stars (1) lose angular momentum before they aredeposited on the birth line, plausibly through star-disk interactions;(2) undergo additional braking as they evolve down their convectivetracks; and (3) are subject to core-envelope decoupling during theconvective-radiative transition.
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VRI photometry of wide double stars with A- type primaries.
We are presenting VRI photometry of 93 wide visual double stars havinglate B- or A- type primaries, taken from the Annex of Double andMultiple Stars of the HIPPARCOS Input Catalogue. Spectral types havebeen estimated for most of the primaries and for the majority of thesecondaries. 40% of them probably have common origin components, forwhich we calculated photometric parallaxes and some orbital valuesestimates.
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Far-ultraviolet stellar photometry: A field in Orion
Far-ultraviolet photometry for 625 objects in Orion is presented. Thesedata were extracted from electrographic camera images obtained duringsounding rocket flights in 1975 and 1982. The 1975 images were centeredclose to the belt of Orion while the 1982 images were centeredapproximately 9 deg further north. One hundred and fifty stars fell inthe overlapping region and were observed with both cameras. Sixty-eightpercent of the objects were tentatively identified with known starsusing the SIMBAD database while another 24% are blends of objects tooclose together to separate with our resolution. As in previous studies,the majority of the identified ultraviolet sources are early-type stars.However, there are a significant number for which no such identificationwas possible, and we suggest that these are interesting objects whichshould be further investigated. Seven stars were found which were brightin the ultraviolet but faint in the visible. We suggest that some ofthese are nearby white dwarfs.
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Liste des étoiles Ap et Am dans les amas ouverts (édition révisée)
Not Available
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Machine-readable version of the Parenago catalogue of stars in the area of the Orion nebula
Not Available
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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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Liste des étoiles Ap et Am dans les amas ouverts (Edition révisée)
Not Available
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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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Properties of AM stars in the Geneva photometric system
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&A....92..289H&db_key=AST
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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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Classificazione spettrale con prisma obiettivo di stelle del complesso Orione
Not Available
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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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A Study of the Orion Aggregate of Early-Type Stars. II.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1954ApJ...119..200S&db_key=AST
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Catalogue of stars in the area of the Orion Nebula.
Not Available
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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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