WIKISKY.ORG
 Home Getting Started To Survive in the Universe News@Sky Astro Photo The Collection Forum Blog New! FAQ Press Login

ζα CrB

Contents

Images

DSS Images   Other Images

Related articles

 3D mapping of the dense interstellar gas around the Local BubbleWe present intermediate results from a long-term program of mapping theneutral absorption characteristics of the local interstellar medium,motivated by the availability of accurate and consistent parallaxes fromthe Hipparcos satellite. Equivalent widths of the interstellar NaID-line doublet at 5890 Å are presented for the lines-of-sighttowards some 311 new target stars lying within ~ 350 pc of the Sun.Using these data, together with NaI absorption measurements towards afurther ~ 240 nearby targets published in the literature (for many ofthem, in the directions of molecular clouds), and the ~ 450lines-of-sight already presented by (Sfeir et al. \cite{sfeir99}), weshow 3D absorption maps of the local distribution of neutral gas towards1005 sight-lines with Hipparcos distances as viewed from a variety ofdifferent galactic projections.The data are synthesized by means of two complementary methods, (i) bymapping of iso-equivalent width contours, and (ii) by densitydistribution calculation from the inversion of column-densities, amethod devised by Vergely et al. (\cite{vergely01}). Our present dataconfirms the view that the local cavity is deficient in cold and neutralinterstellar gas. The closest dense and cold gas wall'', in the firstquadrant, is at ~ 55-60 pc. There are a few isolated clouds at closerdistance, if the detected absorption is not produced by circumstellarmaterial.The maps reveal narrow or wide interstellar tunnels'' which connectthe Local Bubble to surrounding cavities, as predicted by the model ofCox & Smith (1974). In particular, one of these tunnels, defined bystars at 300 to 600 pc from the Sun showing negligible sodiumabsorption, connects the well known CMa void (Gry et al. \cite{gry85}),which is part of the Local Bubble, with the supershell GSH 238+00+09(Heiles \cite{heiles98}). High latitude lines-of-sight with the smallestabsorption are found in two chimneys'', whose directions areperpendicular to the Gould belt plane. The maps show that the LocalBubble is squeezed'' by surrounding shells in a complicated patternand suggest that its pressure is smaller than in those expandingregions.We discuss the locations of several HI and molecular clouds. Usingcomparisons between NaI and HI or CO velocities, in some cases we areable to improve the constraints on their distances. According to thevelocity criteria, MBM 33-37, MBM 16-18, UT 3-7, and MBM 54-55 arecloser than ~ 100 pc, and MBM 40 is closer than 80 pc. Dense HI cloudsare seen at less than 90 pc and 85 pc in the directions of the MBM 12and MBM 41-43 clouds respectively, but the molecular clouds themselvesmay be far beyond. The above closest molecular clouds are located at theneutral boundary of the Bubble. Only one translucent cloud, G192-67, isclearly embedded within the LB and well isolated.These maps of the distribution of local neutral interstellar NaI gas arealso briefly compared with the distribution of both interstellar dustand neutral HI gas within 300 pc.Tables 1 and 2 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp:cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/411/447 Rotational Velocities of B StarsWe 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. Zeta$^2$ Coronae Borealis, A Spectroscopic Triple System Including an Asynchronous Close BinaryUsing the 1-m telescope at Ritter Observatory, we took 36 observationsof \zeta$^2$ Coronae Borealis with a fiber-fed echelle spectrograph.From these observations, \zeta$^2$ CrB was found to be a triple systemand a new spectroscopic orbit was calculated. This orbit has twoperiods, a 1.72357 day period for the inner binary composed of \zeta$^2$CrB A $&$ B and a 251 day period for the outer binary compsed of\zeta$^2$ CrB AB $&$ C. The inner binary is a double-linedspectroscopic binary composed of two B7 V stars. The inner binary`scenter of mass (\zeta$^2$ CrB AB) describes a long-period single-linedvariation identified with the outer binary. The inner binary period issignificantly shorter than the 12.5842 day period previously calculatedby Abhyankar $&$ Sarma (1966). The inner binary possesses anessentially circular orbit $(e = 0.48)$. From the widths of their Si II6371 \AA lines, the \upsilon sin $i$'s were calculated to be 46 \pm 7 kms$^-1$ for \zeta$^2$ CrB A and 7.5 \pm 2 km s$^-1$ for \zeta$^2$ CrB B.As \zeta$^2$ CrB A $&$ B have similar masses, their differentrotational velocities make this system a sensitive test ofsynchronization theories. (SECTION: Stars) 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. ICCD speckle observations of binary stars. I - A survey for duplicity among the bright starsA survey of a sample of 672 stars from the Yale Bright Star Catalog(Hoffleit, 1982) has been carried out using speckle interferometry onthe 3.6-cm Canada-France-Hawaii Telescope in order to establish thebinary star frequency within the sample. This effort was motivated bythe need for a more observationally determined basis for predicting thefrequency of failure of the Hubble Space Telescope (HST) fine-guidancesensors to achieve guide-star lock due to duplicity. This survey of 426dwarfs and 246 evolved stars yielded measurements of 52 newly discoveredbinaries and 60 previously known binary systems. It is shown that thefrequency of close visual binaries in the separation range 0.04-0.25arcsec is 11 percent, or nearly 3.5 times that previously known. Photographic observations of bright stars in the declination zone from +40 to +90 deg with a normal astrograph and 26-arcsec refractor at PulkovoNot Available Catalogue of the energy distribution data in spectra of stars in the uniform spectrophotometric system.Not Available Four-colour photometry of B stars north of B = + 45 deg and comparison with the southFour-color photometry of 33 Henry Draper B stars north of b = + 45 degis presented. Most are little-reddened B or intermediate-A stars. A newAm star is discovered. The new measures essentially complete uvbyphotometry of all HD B stars within 45 deg of either galactic pole. Thenorthern and southern cones of HD B stars are compared, and selectioneffects deduced. Far from the galactic plane, it appears that B starsmay be equally distributed north and south of the plane; closer to thesun, an asymmetry associated with Gould's Belt is evident. Photometric and astrometric observations of close visual binariesThe first photoelectric sequence for the magnitude differences of 215close visual binaries in the Johnson UBV and Stromgren uvby systems havebeen established. In addition, the position angle and the separation of140 stars were measured. Finally, for 134 stars, new photoelectricmeasurements of the combined integral brightness of both components inthe UBV and Stromgren systems were made. The measurements were carriedout using the area scanning technique. Visual Double Stars for the AmateurNot Available Erratum - Discordances Between SAO and HD Numbers for Bright StarsNot Available Spectral classification from the ultraviolet line features of S2/68 spectra. V - Supplement seriesThe paper presents the ultraviolet classification of more than 450 B-Aand F spectra obtained with the sky survey telescope mounted on the TD1satellite. Concerning abnormal objects, attention is given to the Bestars, the binary stars, the helium weak stars, and the lambda Booobjects. With regard to Be stars, it is concluded that the 1930 Awavelength feature is linked to the existence of either shell structuresor Fe II emission lines in the visual spectral range. In addition, it issuggested that stellar spectra at wavelengths of 1410, 1610-20 and 2400A are equivalent to the He-weak group in the classical range. Late B-type stars - Rotation and the incidence of HgMn starsHigh-dispersion spectrograms for an unbiased sample of 256 late B-typestars are examined in an attempt to determine whether slow rotation isnecessary and sufficient for the appearance of HgMn anomalies innonmagnetic stars. The peculiar stars in the sample are identified,values of v sin i are derived for all the stars observed, and theradial-velocity variations of the identified HgMn stars are analyzed.The distribution of rotational velocities for late B-type stars isobtained, and the role of rotation in producing extended envelopes isevaluated. The binary frequency and mass-ratio distribution are derivedfor systems containing HgMn components, the effect of duplicity on thedistribution of rotational velocities is estimated, and the role of suchfactors as rotation, age, and binary characteristics in determiningwhether HgMn anomalies are present is investigated. The results clearlyshow that HgMn stars occur only within a limited temperature range, thatall such stars rotate slowly, but that rotation, effective temperature,age, surface gravity, and binary properties do not serve to determinewhether a star will exhibit abundance anomalies. Duplicity of late B-type starsHigh-dispersion spectroscopic observations of 83 stars are used todetermine the binary characteristics of late B-type stars. For a randomsample of such objects, including peculiar as well as normal stars, thefrequency of binaries with mass ratios m2/m sub 1 greaterthan 0.1 and orbital periods less than 100 days is estimated to be about24%, and the frequency of binaries decreases with decreasingm2/m sub 1. In both respects, the late B-type stars aresimilar to early B-, late A-, and solar-type stars. For the majority ofstars with an orbital period greater than 4 days, the observedrotational velocity exceeds the value that corresponds to synchronism ofrotation and revolution, but the ratio of the observed to thesynchronous rotational velocity seldom exceeds a factor of 2 even forperiods as long as 15 days. An additional 20% of the stars surveyedexhibit low amplitude-velocity variations that, if due to orbitalmotion, correspond to m2 m1 less than 0.1. Themost likely explanation is that these systems are close binary remnantsthat have already passed through the mass-transfer phase, with thepresent secondary being a white dwarf. Photographic measures of double stars. IIMeasures are presented for 302 double stars photographed on 657 plateswith the 36-in. Lick refractor in the period between 1945 and 1962. Thedata provided include the observing epochs, the rectangular coordinatesof the secondary components with reference to the respective primaries,the mean errors of a single measurement, the computed mean errors, thedouble-star separations, and the position angles both for the observingepoch and reduced to the equator of 2000. An additional 561 unmeasuredplates of acceptable quality obtained between 1948 and 1960 are listed. 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 The manganese starsUltraviolet spectrograms of 194 middle and late B-type stars wereobtained in a search for Mn stars. The 24 Mn stars found in this searchlay within the limited temperature range from 0.33 to 0.48. Theirobserved rate of incidence and rotational velocity distributionsubstantiate the hypothesis that the Mn stars constitute a considerablefraction of the slowly rotating stars in this temperature range. If theatmospheres of these stars are sufficiently stable for diffusionprocesses to be effective, then it also becomes possible to account forthe temperature range in which the Mn overabundance occurs. Four-color and H beta photometry for the bright B8 and B9 type stars north of declination -10 degre.Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973AJ.....78..738C&db_key=AST Spectral classification of the bright B8 stars.Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972AJ.....77..750C&db_key=AST Narrow-band photometry of early-type stars.Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971A&A....12....5H&db_key=AST A spectroscopic investigation of visual binaries with B-type primaries.Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1969AJ.....74.1082M&db_key=AST A study of the spectroscopic binary ζ CrB AAbstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1966MNRAS.133..437A&db_key=AST Mouvement relatif linéaire d'étoiles doublesNot Available U, b, v, and Hβ Photometry for the Bright B8- and B9-TYPE Stars.Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1963ApJ...137..530C&db_key=AST Recherches sur les Proprietes des Etoiles Doubles ou Multiples Largement Separees EN Relation avec les Problemes d'EvolutionNot Available Double star measurements with a polarising micrometer.Not Available A Study of Some Early Type Close Binary Stars.Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1959ApJS....4..157A&db_key=AST Spectral Classification of 533 B8-A2 Stars and the Mean Absolute Magnitude of a0 V Stars.Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1959ApJ...130..159O&db_key=AST Mesures d'étoiles doubles faites à l' équatorial de 215 mm de l'Observatoire de la Sté Astronomique de FranceNot Available
Submit a new article

• - No Links Found -