Оглавление
Изображения
Загрузить ваше изображение
DSS Images Other Images
Публикации по объекту
Evolution of interacting binaries with a B type primary at birth
We revisited the analytical expression for the mass ratio distributionfor non-evolved binaries with a B type primary. Selection effectsgoverning the observations were taken into account in order to comparetheory with observations. Theory was optimized so as to fit best withthe observed q-distribution of SB1s and SB2s. The accuracy of thistheoretical mass ratio distribution function is severely hindered by theuncertainties on the observations. We present a library of evolutionarycomputations for binaries with a B type primary at birth. Some liberalcomputations including loss of mass and angular momentum during binaryevolution are added to an extensive grid of conservative calculations.Our computations are compared statistically to the observeddistributions of orbital periods and mass ratios of Algols. ConservativeRoche Lobe Over Flow (RLOF) reproduces the observed distribution oforbital periods but fails to explain the observed mass ratios in therange q in [0.4-1]. In order to obtain a better fit the binaries have tolose a significant amount of matter, without losing much angularmomentum.
| A Galactic O Star Catalog
We have produced a catalog of 378 Galactic O stars with accuratespectral classifications that is complete for V<8 but includes manyfainter stars. The catalog provides cross-identifications with othersources; coordinates (obtained in most cases from Tycho-2 data);astrometric distances for 24 of the nearest stars; optical (Tycho-2,Johnson, and Strömgren) and NIR photometry; group membership,runaway character, and multiplicity information; and a Web-based versionwith links to on-line services.
| A study of RV in Galactic O stars from the 2MASS catalogue
We present new measurements of the interstellar reddening parameterRV=AV/E(B-V) towards 185 O stars, using J, H,Ks photometry from the 2MASS project. The results arecombined with data from the literature of 95 stars where RVhas been derived with the same technique, 22 of which in common with ourpresent sample from the 2MASS project catalogue. The averageRV from these 258 O stars is of 3.19 +/- 0.50. All objectswhose RV departs from this value by more than 2 sigma havebeen recognized. Ten objects have RV higher than this valueand two lower. It is found that anomalous RV can scarcely beassociated with anomalies in the general interstellar medium, e.g. withdifferent behaviour in different spiral arms. They are clearly linked tolocal cloud effect. In the Cygnus region RV values follow thebehaviour of the general interstellar medium, while in the Carina arm,in spite of the relatively larger distance, local cloud effects prevail.An explanation for this is suggested. The relatively few stars of oursample whose Hipparcos parallaxes are reliable, are found to havedistances systematically smaller than the distances derived by thespectroscopic parallaxes. We argue that this effect is consistent withthe recently claimed discovery of grey extinction towards OB stars.This publication makes use of data products from the Two Micron All SkySurvey (2MASS), which is a joint project of the University ofMassachusetts and the Infrared Processing and Analysis Center/CaliforniaInstitute of Technology, funded by the National Aeronautics and SpaceAdministration and the National Science Foundation.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/410/905
| Masses and other parameters of massive binaries
Binary stars provide us with the means to measure stellar mass. Here Ipresent several lists of known O-type stars with reliable mass estimatesthat are members of eclipsing, double-lined spectroscopic binaries. Themasses of young, unevolved stars in binaries are suitable for testingthe predictions of evolutionary codes, and there is good agreementbetween the observed and predicted masses (based upon temperature andluminosity) if the lower temperature scale from line-blanketed modelatmospheres is adopted. A final table lists masses for systems in awide variety of advanced evolutionary stages.
| On the Absolute Magnitudes of the O Stars
The conclusion published in 1992 by Garmany & Stencel from a studyof northern OB associations, that the absolute magnitudes of the O starsshow ``a large scatter ... intrinsic to the classification system,'' iscritically examined. It is found that the differences between theirderived absolute magnitudes of O stars and this author's 1973calibration exhibit large systematic effects in several associations,ranging from -0.74 to +1.02 mag with substantially smaller dispersions.Of course, when these results are combined, the scatter equals the fullrange of the systematic effects. To investigate the possibility ofdistance errors, the Garmany & Stencel B0-B2.5 stars in the sameassociations are subjected to the same analysis. The results for the Bstars show no significant systematic differences, eliminating errors inthe association distances derived by Garmany & Stencel from the Bstars as the source of the differences found for the O stars. It isnoteworthy that the dispersions in the absolute magnitudes of the Bstars within a given association are similar to or larger than those ofthe O stars. An examination of the distribution on the sky of the starsshows that the O and B stars in the discrepant associations aregenerally not colocated; such was already known to be the case for theimportant Perseus OB1 association. It is suggested that despite theirefforts to improve them, significant problems remain with theassociation memberships adopted by Garmany & Stencel; the relativelysmall dispersions of the O star absolute magnitudes even in thediscrepant cases indicate that they belong to different, usually moredistant associations near the lines of sight to the B associations withwhich they have been mistakenly connected. Several individual cases ofunrecognized multiple systems and classification errors are also foundin the Garmany & Stencel sample. It is concluded that the scatter inthe absolute magnitudes of the O stars is not as large as found byGarmany & Stencel, and not larger than that of the B stars.
| Determination of R_V towards galactic O stars
We present new measurements of the interstellar reddening parameterRV=AV/E(B-V) towards 35 O stars. The results arecombined with measurements from the literature for 60 stars to study thebehaviour of RV with heliocentric distance. RV isthe single basic parameter which characterizes the interstellarextinction from the near-infrared to the far-UV spectral region. Theabsolute extinction AV, from which RV is derived,is best determined by optical and near-infrared photometry (Cardelli etal. \cite{r3}). We consider important the derivation of RVwith the same technique in the direction of as many as possible galacticO stars.
| Absolute proper motions of open clusters. I. Observational data
Mean proper motions and parallaxes of 205 open clusters were determinedfrom their member stars found in the Hipparcos Catalogue. 360 clusterswere searched for possible members, excluding nearby clusters withdistances D < 200 pc. Members were selected using ground basedinformation (photometry, radial velocity, proper motion, distance fromthe cluster centre) and information provided by Hipparcos (propermotion, parallax). Altogether 630 certain and 100 possible members werefound. A comparison of the Hipparcos parallaxes with photometricdistances of open clusters shows good agreement. The Hipparcos dataconfirm or reject the membership of several Cepheids in the studiedclusters. Tables 1 and 2 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Two-colour photometry for 9473 components of close Hipparcos double and multiple stars
Using observations obtained with the Tycho instrument of the ESAHipparcos satellite, a two-colour photometry is produced for componentsof more than 7 000 Hipparcos double and multiple stars with angularseparations 0.1 to 2.5 arcsec. We publish 9473 components of 5173systems with separations above 0.3 arcsec. The majority of them did nothave Tycho photometry in the Hipparcos catalogue. The magnitudes arederived in the Tycho B_T and V_T passbands, similar to the Johnsonpassbands. Photometrically resolved components of the binaries withstatistically significant trigonometric parallaxes can be put on an HRdiagram, the majority of them for the first time. Based on observationsmade with the ESA Hipparcos satellite.
| UBV beta Database for Case-Hamburg Northern and Southern Luminous Stars
A database of photoelectric UBV beta photometry for stars listed in theCase-Hamburg northern and southern Milky Way luminous stars surveys hasbeen compiled from the original research literature. Consisting of over16,000 observations of some 7300 stars from over 500 sources, thisdatabase constitutes the most complete compilation of such photometryavailable for intrinsically luminous stars around the Galactic plane.Over 5000 stars listed in the Case-Hamburg surveys still lackfundamental photometric data.
| ICCD speckle observations of binary stars. XIX - an astrometric/spectroscopic survey of O stars
We present the results of a speckle interferometric survey made with theCHARA speckle camera and 4 m class telescopes of Galactic O-type starswith V less than 8. We can detect with the speckle camera binaries inthe angular separation range 0.035-1.5 arcsec with delta M less than 3,and we have discovered 15 binaries among 227 O-type systems. We combinedour results on visual binaries with measurements of wider pairs from theWashington Double Star Catalog and fainter pairs from the HipparcosCatalog, and we made a literature survey of the spectroscopic binariesamong the sample. We then investigated the overall binary frequency ofthe sample and the orbital characteristics of the known binaries.Binaries are common among O stars in clusters and associations but lessso among field and especially runaway stars. There are many triplesystems among the speckle binaries, and we discuss their possible rolein the ejection of stars from clusters. The period distribution of thebinaries is bimodal in log P, but we suggest that binaries with periodsof years and decades may eventually be found to fill the gap. The massratio distribution of the visual binaries increases toward lower massratios, but low mass ratio companions are rare among close,spectroscopic binaries. We present distributions of the eccentricity andlongitude of periastron for spectroscopic binaries with ellipticalorbits, and we find strong evidence of a bias in the longitude ofperiastron distribution.
| Kinematic signatures of violent formation of galactic OB associations from HIPPARCOS measurements
Proper motions measured by Hipparcos confirm the large anomalousvelocities of the OB associations located around the Cygnus Superbubble(Cygnus OB1, OB3, OB7, and OB9), and reveal a clearly organizedexpanding pattern in Canis Major OB1. At the distances of theseassociations, the organized velocity patterns imply LSR velocities of upto ~ 60 km s(-1) for the associations in Cygnus, and about ~ 15 km s(-1)in Canis Major OB1. The magnitude and spatial arrangement of theexpanding motions suggests that very energetic phenomena are responsiblefor the formation of the present OB associations. This is independentlysupported by observations of the associated interstellar medium carriedout in other wavelengths. The gravitational instability scenarioproposed by Comeron & Torra 1994 (ApJ 423, 652) to account for theformation of the stars in the Cygnus Superbubble region is reviewed inthe light of the new kinematic data. It is found that the energeticrequirements set by the highest velocities on the OB associationpowering the Superbubble, Cygnus OB2, are too large by orders ofmagnitude. However, the scenario can still account for the formation ofmost of the stars if, as can be reasonably expected, the stars with thehighest measured velocities are actually runaways from Cygnus OB2itself. As for Canis Major OB1, we consider their formation in asupernova remnant, as suggested by Herbst & Assousa 1977 (ApJ, 217,473). The detection of a new runaway star, HIC 35707 (=HD 57682), whosemotion is directed away from the derived center of expansion, supportsthis scenario and provides an independent age for the supernova remnant,assuming that the runaway star was the binary companion of thesupernova. Based on a number of arguments, however, we find it unlikelythat the stars are a direct consequence of instabilities in theexpanding shell. We propose instead that their formation was triggeredin preexisting clouds, accelerated and compressed by the supernovaexplosion.
| Flux Distributions for 59 Stars in Cygnus
Absolute flux distributions are given for 59 Cygnus stars in thespectral range of 320--720 nm with a step of 5 nm. Their rms errors areon the average 2--4%. The synthetic color indices calculated for theflux distributions are compared with the observed color indices in threephotometric systems.
| The ``Mass Discrepancy'' for Massive Stars: Tests of Models Using Spectroscopic Binaries
Stellar evolutionary models are often used to infer a star's mass viaits luminosity, but empirical checks on the accuracy of the theoreticalmass-luminosity relation for very massive stars have been lacking. Thisis of particular concern given that modern atmosphere models yieldsystematically smaller masses for massive stars than do evolutionarymodels, with the discrepancy being a factor of 2 for Of stars. Weattempt to resolve this mass discrepancy by obtaining new,high-resolution optical data on seven early-type spectroscopic binaries:V453 Cyg, HD 191201, V382 Cyg, Y Cyg, HD 206267, DH Cep, and AH Cep. Ourstudy produces improved spectral subtypes for the components of thesesystems, which are crucial for evaluating their luminosities andlocations in the H-R diagram. Our radial velocity study utilizes ameasuring method that explicitly accounts for the effects of pairblending. We combine our new orbit solutions with existing data oninclinations and distances when available to compare the orbital masseswith evolutionary models, and we find good agreement in all cases wherethe stars are noninteracting. (The components of V382 Cyg and DH Cepfill their Roche lobes, and in both cases we find masses substantiallylower than the masses inferred from evolutionary tracks, suggesting thatsignificant material has been lost rather than transferred. We confirmthat this same trend exists for other systems drawn from theliterature.) Our own data extends to only 15 Mȯ, althoughphotometric inclination determinations for HD 191201 and HD 206267should prove possible and will provide examples of higher mass systems.We briefly discuss suitable systems from the literature and concludethat orbit solutions provide good agreement with the evolutionary modelsto 25 Mȯ. Beyond this, most known binaries either fill their Rochelobes or have other complications. We also discuss five systems forwhich our improved data and analysis failed to yield acceptable orbitsolutions: EO Aur, IU Aur, V640 Mon (Plaskett's star), LY Aur, and 29 UWCMa all remained intractable, despite improved data.
| MSC - a catalogue of physical multiple stars
The MSC catalogue contains data on 612 physical multiple stars ofmultiplicity 3 to 7 which are hierarchical with few exceptions. Orbitalperiods, angular separations and mass ratios are estimated for eachsub-system. Orbital elements are given when available. The catalogue canbe accessed through CDS (Strasbourg). Half of the systems are within 100pc from the Sun. The comparison of the periods of close and widesub-systems reveals that there is no preferred period ratio and allpossible combinations of periods are found. The distribution of thelogarithms of short periods is bimodal, probably due to observationalselection. In 82\% of triple stars the close sub-system is related tothe primary of a wide pair. However, the analysis of mass ratiodistribution gives some support to the idea that component masses areindependently selected from the Salpeter mass function. Orbits of wideand close sub-systems are not always coplanar, although thecorresponding orbital angular momentum vectors do show a weak tendencyof alignment. Some observational programs based on the MSC aresuggested. Tables 2 and 3 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| 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.
| The Initial Mass Function and Massive Star Evolution in the OB Associations of the Northern Milky Way
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJ...454..151M&db_key=AST
| Radio continuum emission from stars: a catalogue update.
An updated version of my catalogue of radio stars is presented. Somestatistics and availability are discussed.
| An IUE survey of interstellar H I LY alpha absorption. 1: Column densities
We measure Galactic interstellar neutral hydrogen column densities byanalyzing archival interstellar Ly alpha absorption line data toward 554B2 and hotter stars observed at high resolution with the IUE satellite.This study more than doubles the number of lines of sight with measuresof N(H I) based on Ly alpha. We have included the scattered lightbackground correction algorithm of Bianchi and Bohlin in our datareduction. We use the correlation between the Balmer discontinuity(c1) index and the stellar Ly alpha absorption in order toassess the effects of stellar Ly alpha contamination. Approximately 40%of the B stars with measured (c1) index, exhibit seriousstellar Ly alpha contamination. One table contains the derived values ofthe interstellar N(H I) for 393 stars with at most small amounts ofstellar contamination. Another lists the observed values of total N(H I)for 161 stars with suspected stellar Ly alpha contamination and/oruncertain stellar parameters.
| Synthetic UV Lines of Si IV, C IV, and He II from a Population of Massive Stars in Starburst Galaxies
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993ApJ...418..749R&db_key=AST
| The violent interstellar environment around the Wolf-Rayet star HD 192163
IRAS Skyflux IR images, high-dispersion IUE UV spectra, optical spectra,and optical interference filter images are used to investigate thenature of the interstellar environment around the Wolf-Rayet star HD192163. IRAS images show an apparent 1.5 x 1.8 deg IR emission shellvery nearly centered on HD 192163, which is designated G75.5+2.4. It issuggested that this shell is a possible unrecognized SNR with anestimated age of not less than 100,000 yr if at the assumed 1.8-kpcdistance of HD 192163. A well-defined 2 x 4.5 deg region of weak IRemission lying to the southeast of HD 192163 appears to be the IRsignature of the Cyg OB1 superbubble. Analysis of IUE spectra shows thathigh-velocity components of UV interstellar absorption lines are presentfor both high and low ionization lines in 18 of 22 stars located in theCyg OB1/OB3 direction with a velocity range of +/- 90 km/s. A possibleevolutionary history for this region is outlined.
| Galactic OB associations in the northern Milky Way Galaxy. I - Longitudes 55 deg to 150 deg
The literature on all OB associations was reviewed, and their IRAS pointsource content was studied, between galactic longitude 55 and 150 deg.Only one third of the 24 associations listed by Ruprecht et al. (1981)have been the subject of individual studies designed to identify thebrightest stars. Distances to all of these were recomputed using themethod of cluster fitting of the B main sequence stars, which makes itpoossible to reexamine the absolute magnitude calibration of the Ostars, as well as for the red supergiant candidate stars. Also examinedwas the composite HR diagram for these associations. Associations withthe best defined main sequences, which also tend to contain very youngclusters, referred to here as OB clusters, have extremely few evolved Band A or red supergiants. Associations with poorly defined mainsequences and few OB clusters have many more evolved stars. They alsoshow an effect in the upper HR diagram referred to as a ledge byFitzpatrick and Garmany (1990) in similar data for the Large MagellanicCloud. It is suggested that the differences in the associations are notjust observational selection effects but represent real differences inage and formation history.
| Close binary systems in regions of open clusters. I - V448 CYG in NGC 6871
New photoelectric UBVRI' observations of the massive early-typeeclipsing system V448 Cyg in the open cluster NGC 6871 were obtained.The light curve is found to be variable in all colors. The period of thesystem is modified. New photometric elements of V448 Cyg are determinedby Lavrov's method, and absolute parameters of the system are estimated.Difficulties in interpreting the larger-size low-mass component arediscussed. The distance to V448 Cyg is estimated at 11.2 m, and its ageis 8,000,000 yr.
| Close binaries observed polarimetrically
Not Available
| Photospheric Absorption Lines in the Ultraviolet Spectra of O-Stars and B-Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990MNRAS.246..392P&db_key=AST
| Empirical temperature calibrations for early-type stars
Three temperature calibrations of suitable photometric quantities havebeen derived for O and B stars. A sample of 120 stars with reliableT(eff.) determinations has been used for establishing each calibration.The different calibrations have been critically discussed and compared.Temperature determinations for 1009 program stars have been obtainedwith an accuracy of the order of 10 percent.
| The stellar winds of 203 Galactic O stars - A quantitative ultraviolet survey
Measurements of the resonance lines of C IV, N V, and Si IV in a sampleof 203 O stars observed using IUE in a high-resolution mode arepresented. The data are discussed using a consistent set of radius,luminosity, and mass estimates. The ratio of the maximum observedvelocity and the terminal (farfield) velocity is found to average at 3.0for 131 stars with strong or saturated lines, and at 2.6 for all stars.An expression is given which is the best available predictor of O starmass loss rates, giving an accuracy better than a factor of twoirrespective of luminosity class. The ionization fractions C(3+)/C andN(4+)/N are found to be independent of stellar effective temperature,but increase by a factor of about two from main sequence stars tosupergiants. Two new possible ON stars are identified, and enhancedsurface nitrogen abundance is confimed in ON stars. Discrete narrowabsorption features are found to be virtually universal characteristicof O star P Cygni profiles.
| A photoelectric search for variable stars in the open cluster NGC 6871.
Not Available
| E(B-V) determination from an UV-visual two-colour diagram - O and B stars in the Catalogue of Stellar Ultraviolet Fluxes
For the O and B type stars in the Catalogue of Stellar UltravioletFluxes, an approach is presented which does not require a preciseknowledge of spectral type and luminosity class for deriving E(B-V)color excesses. The method is based on the use of an UV-visual two-colordiagram; galactic variations in the interstellar extinction law areanalyzed and fully taken into account. The results have been comparedwith those derived by using the differences between observed andintrinsic colors for stars with known spectral classification. The verygood agreement in a large number of cases (94 percent) demonstrates thatthe present approach permits the derivation of reliable color excessvalues for early-type stars even if only a rough spectral classificationis available.
| The kinematical and binary properties of association and field O stars
A catalog of 195 Galactic O-type stars brighter than V = 8.0 mag hasbeen compiled to compare the velocity distribution and binary frequencyamong cluster and association, field, and runaway stars. Both the fieldstars and runaway stars have a larger dispersion in peculiar radialvelocity, a more positive mean peculiar radial velocity, and a widerz-distribution than stars found in clusters and associations, which isconsistent with the ejection of field and runaway stars from theirbirthplaces in associations. Visual binaries are common among stars inclusters and associations, but their incidence is a factor of 2 loweramong field stars, and they are absent in the runaway stars. Similarly,there is a deficiency of spectroscopic binaries among field stars, andespecially the runaway stars, relative to the numbers found in clustersand associations. Many of these properties can be understood in terms ofejection through close gravitational interactions with binary starsduring an early high number density epoch in the evolution of clusters.
| The interstellar 217 NM band - A third catalogue of equivalent widths
A catalog of equivalent widths of the 217 nm interstellar absorptionband as well as other parameters characterizing the extinction curve inthe ultraviolet has been compiled for 790 O and B stars. A relativelytight correlation between the equivalent width of the 217 nm band andE(B-V) indicates that the absorber of this band is connected with thepopulation of larger interstellar grains responsible for the visualextinction. The parameter characterizing the amount of extinction in thefar UV is only weakly correlated with E(B-V), a result in accord withthe assumption that a second population of very small grains causes therapid increase of the far-UV extinction.
|
Добавить новую статью
Внешние ссылки
- - Внешних ссылок не найдено -
Добавить внешнюю ссылку
Группы:
|
Наблюдательные данные и астрометрия
| Созвездие: | Лебедь |
| Прямое восхождение: | 20h07m23.69s |
| Склонение: | +35°43'05.9" |
| Видимая звёздная величина: | 7.437 |
| Расстояние: | 751.88 парсек |
| Собственное движение RA: | -6.6 |
| Собственное движение Dec: | -2.4 |
| B-T magnitude: | 7.576 |
| V-T magnitude: | 7.449 |
Каталоги и обозначения:
|
