|B Star Rotational Velocities in h and χ Persei: A Probe of Initial Conditions during the Star Formation Epoch?|
Projected rotational velocities (vsini) have been measured for 216 B0-B9stars in the rich, dense h and χ Persei double cluster and comparedwith the distribution of rotational velocities for a sample of fieldstars having comparable ages (t~12-15 Myr) and masses (M~4-15Msolar). For stars that are relatively little evolved fromtheir initial locations on the zero-age main sequence (ZAMS) (those withmasses M~4-5 Msolar), the mean vsini measured for the h andχ Per sample is slightly more than 2 times larger than the meandetermined for field stars of comparable mass, and the cluster and fieldvsini distributions differ with a high degree of significance. Forsomewhat more evolved stars with masses in the range 5-9Msolar, the mean vsini in h and χ Per is 1.5 times thatof the field; the vsini distributions differ as well, but with a lowerdegree of statistical significance. For stars that have evolvedsignificantly from the ZAMS and are approaching the hydrogen exhaustionphase (those with masses in the range 9-15 Msolar), thecluster and field star means and distributions are only slightlydifferent. We argue that both the higher rotation rates and the patternof rotation speeds as a function of mass that differentiatemain-sequence B stars in h and χ Per from their field analogs werelikely imprinted during the star formation process rather than a resultof angular momentum evolution over the 12-15 Myr cluster lifetime. Wespeculate that these differences may reflect the effects of the higheraccretion rates that theory suggests are characteristic of regions thatgive birth to dense clusters, namely, (1) higher initial rotationspeeds; (2) higher initial radii along the stellar birth line, resultingin greater spin-up between the birth line and the ZAMS; and (3) a morepronounced maximum in the birth line radius-mass relationship thatresults in differentially greater spin-up for stars that become mid- tolate-B stars on the ZAMS.
|A New Bright Helium Variable B Star: HR 2949|
We report high-resolution spectroscopic observations of HR 2949,revealing the star as Helium variable B star with P=1.9093d.
|Rotational Velocities of B Stars|
We measured the projected rotational velocities of 1092 northern B starslisted in the Bright Star Catalogue (BSC) and calibrated them againstthe 1975 Slettebak et al. system. We found that the published values ofB dwarfs in the BSC average 27% higher than those standards. Only 0.3%of the stars have rotational velocities in excess of two-thirds of thebreakup velocities, and the mean velocity is only 25% of breakup,implying that impending breakup is not a significant factor in reducingrotational velocities. For the B8-B9.5 III-V stars the bimodaldistribution in V can be explained by a set of slowly rotating Ap starsand a set of rapidly rotating normal stars. For the B0-B5 III-V starsthat include very few peculiar stars, the distributions in V are notbimodal. Are the low rotational velocities of B stars due to theoccurrence of frequent low-mass companions, planets, or disks? Therotational velocities of giants originating from late B dwarfs areconsistent with their conservation of angular momentum in shells.However, we are puzzled by why the giants that originate from the earlyB dwarfs, despite having 3 times greater radii, have nearly the samerotational velocities. We find that all B-type primaries in binarieswith periods less than 2.4 days have synchronized rotational and orbitalmotions; those with periods between 2.4 and 5.0 days are rotating withina factor 2 of synchronization or are ``nearly synchronized.'' Thecorresponding period ranges for A-type stars are 4.9 and 10.5 days, ortwice as large. We found that the rotational velocities of the primariesare synchronized earlier than their orbits are circularized. The maximumorbital period for circularized B binaries is 1.5 days and for Abinaries is 2.5 days. For stars of various ages from 107.5 to1010.2 yr the maximum circularized periods are a smoothexponential function of age.
|GasDust Shells around Some Early-Type Stars with an IR Excess (of Emission)|
The results of an investigation of IR (IRAS) observations of 58OBAF stars of different luminosity classes, whichare mainly members of various associations, are presented. The colorindices of these stars are determined and two-color diagrams areconstructed. The emission excesses at 12 and 25 mm (E 12 and E 25) arealso compared with the absorption A1640 of UV radiation. It is concludedthat 24 stars (of the 58 investigated) are disk systems of the Vegatype, to which Vega = N 53 also belongs. Eight known stars of the Vegatype are also given in the figures for comparison. The remaining 34stars may have gasdust shells and/or shelldisks. The IRemission excesses of the 34 investigated stars and 11 comparison stars(eight of them are Be-Ae stars) are evidently due both to thermalemission from grains and to the emission from freefreetransitions of electrons in the gasdust shells of these stars.
|The Pulkovo Spectrophotometric Catalog of Bright Stars in the Range from 320 TO 1080 NM|
A spectrophotometric catalog is presented, combining results of numerousobservations made by Pulkovo astronomers at different observing sites.The catalog consists of three parts: the first contains the data for 602stars in the spectral range of 320--735 nm with a resolution of 5 nm,the second one contains 285 stars in the spectral range of 500--1080 nmwith a resolution of 10 nm and the third one contains 278 stars combinedfrom the preceding catalogs in the spectral range of 320--1080 nm with aresolution of 10 nm. The data are presented in absolute energy unitsW/m(2) m, with a step of 2.5 nm and with an accuracy not lower than1.5--2.0%.
|The ROSAT all-sky survey catalogue of optically bright OB-type stars.|
For the detailed statistical analysis of the X-ray emission of hot starswe selected all stars of spectral type O and B listed in the Yale BrightStar Catalogue and searched for them in the ROSAT All-Sky Survey. Inthis paper we describe the selection and preparation of the data andpresent a compilation of the derived X-ray data for a complete sample ofbright OB stars.
|Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.|
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
|Ultraviolet observations in Puppis with the space telescope 'GLAZAR'|
The results of observations of 159 stars at 1640 A in Puppis made withthe space telescope 'Glazar' are presented. It is shown that theobserved stars are members of different groups of stars situated atdistances of about 120, 370, 700, 1250, 2400, and 4000 pc. The last twogroups belong to the Pup OB1 and Pup OB2 stellar associations. There isrelatively little absorption in the observed region. The absorbingmatter is mainly concentrated in small clouds. It is suggested thatthree stars - CP - 27 deg 4197, HD 60479, and HD 61672 - are embedded ina dust envelope and that the star HD 60057 has a hot subdwarf companion.Forty-four of the observed stars are new OB or early A-type stars,spectral types of which were not known.
|IRAS observations of Post-T-Tauri stars|
Eighty Post-T-Tauri stars in binary systems, located far from dark cloudcomplexes, were checked for far-IR emission, using the IRAS data base.Only seven of them were detected at 12 microns. Most of the stars arefound to radiate normally at 12 microns, having luminosities (L12) inthe range 4 x 10 to the 30th - 3 x 10 to the 33rd ergs/s; this emissionoriginates in the stellar photosphere. There are indications, though,that the younger Post-T-Tauri stars, less than 15 x 10 to the 6th yearsold, possess weak IR excess, possibly due to surrounding dust.
|A catalog of bright UVBY beta standard stars|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1987PASP...99.1184P&db_key=AST
|Catalogue of the energy distribution data in spectra of stars in the uniform spectrophotometric system.|
|A study of visual double stars with early type primaries. IV Astrophysical data|
Astrophysical parameters (MK class, color excess, absolute magnitude,distance, effective temperature, mass, and age) are derived fromcalibrations of the uvby-beta indices for the members of 253 doublestars with O or B type primaries and faint secondaries. The photometricspectral classification is compared to the MK classes, and the agreementis very good. The derived data together with spectroscopic and JHKL dataare used for deciding which pairs are likely to be physical and whichare optical, and it is shown that 98 (34 percent) of the secondaries arelikely to be members of physical systems. For 90 percent of the physicalpairs the projected separation between the components is less than25,000 AU. A majority of the physical secondaries are late-type stars,and 50 percent of them are contracting towards the zero-agemain-sequence. Also presented are new uvby-beta data for 43 secondariesand a computer program for determining astrophysical parameters fromuvby-beta data.
|A photometric study of early-type stars|
Observation data in the alpha(16), Lambda(9) photometric system arepresented for 228 early-type O4-B8 stars of all luminosity classes. Alsoincluded are data for Be stars, B-type stars with a shell, and BetaCanis Majoris stars. The comparison with R-alpha and beta indicessuggests that the alpha(16) photometry is of good quality. Thephotometry can be used in separating different kinds of stars; whencombined with the 13-color photometry, it makes possible a finerclassification. The alpha(16) index also provides an indication ofstellar mass-loss rates, especially for supergiant stars. Preliminary HeI (5876 A) measurements suggest that this line is well correlated withMK types. Be stars observed over several years also exhibit H-alphaline-strength variability. It is found that the Lambda(9) indexseparates supergiant stars later than B2.
|A study of visual double stars with early type primaries. II - Photometric results|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1983A&AS...51..161L&db_key=AST
|A study of visual double stars with early type primaries. I - Spectroscopic results|
Attention is given to spectral peculiarities found in data on thespectral classes of 486 stars in 254 visual doublet or multiplet systemswith O or B type primaries, in order to isolate a group of very youngstars that may serve for the study of early stellar evolutioncharacteristics. It is noted that the material contains a substantialfraction of secondaries that are likely to be physical, and that severalof these may be in the premain-sequence phase of stellar evolution, orhave reached the zero-age main sequence.
|Erratum - Discordances Between SAO and HD Numbers for Bright Stars|
|Combined-light UBV Photometry of 103 Bright Southern Visual Doubles|
|Rotational velocities and spectral types for a sample of binary systems.|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975A&AS...19...91L&db_key=AST
|Statistical Studies in Stellar Rotation. II. a Method of Analyzing Rotational Coupling in Double Stars and an Introduction to its Applications|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972ApJ...177..161B&db_key=AST
|New kinematical data for bright southern OB-stars|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972A&AS....5..129L&db_key=AST
|Standard stars for UVBY photometry.|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970AJ.....75..978C&db_key=AST
|Four-colour and H-beta photometry for bright stars in the southern hemisphere.|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970AJ.....75..624C&db_key=AST
|MK Spectral Types for Bright Southern OB Stars|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1969ApJ...157..313H&db_key=AST
|Catalogue d'etoiles O et B.|
|Photovisual differences in magnitudes of 331 mainly southern double stars|