Upload your image
DSS Images Other Images
Submit a new article
|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.
|Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics|
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (22.214.171.124) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
|Helium and Carbon Abundances in Late-B and Early-A Supergiants|
The abundances of carbon and helium were determined for representativelate-B and early-A supergiants based on the C I lines (9078, 9089, 9095,9112) in the near-IR, C II lines (4267, 6151), and the He I 6678 line,in an aim to investigate the nature of the envelope-mixing in theseevolved stars based on the anomaly (if any) of these elements combinedwith that of N and O published before. It turned out that N tends toincrease with a decrease in C, showing a tendency of conserving the sumof C+N nuclei, which suggests that the anomaly of C and N may bereasonably interpreted as being due to mixing of the CN-processedmaterial. However, this increase/decrease in N/C, indicative ofdredge-up of the H-burning product, is not accompanied by anyHe-enrichment. Even surprisingly, the observed tendency is just theopposite, i.e., [He/H] appears to decrease progressively in accordancewith a lowering of [C/H]. Instead of regarding this apparentcharacteristics as being real, we tentatively speculate that someactivity-related line-weakening mechanism (e.g., irradiance of X-rays)might act on the formation of He I lines, the extent of which isindirectly related to the efficiency of envelope mixing via stellarrotation.
|A Second Catalog of Orbiting Astronomical Observatory 2 Filter Photometry: Ultraviolet Photometry of 614 Stars|
Ultraviolet photometry from the Wisconsin Experiment Package on theOrbiting Astronomical Observatory 2 (OAO 2) is presented for 614 stars.Previously unpublished magnitudes from 12 filter bandpasses withwavelengths ranging from 1330 to 4250 Å have been placed on thewhite dwarf model atmosphere absolute flux scale. The fluxes wereconverted to magnitudes using V=0 for F(V)=3.46x10^-9 ergs cm^-2 s^-1Å^-1, or m_lambda=-2.5logF_lambda-21.15. This second catalogeffectively doubles the amount of OAO 2 photometry available in theliterature and includes many objects too bright to be observed withmodern space observatories.
|Galactic B-supergiants: A non-LTE model atmosphere analysis to estimate atmospheric parameters and chemical compositions|
A non-LTE model atmosphere analysis of moderate resolution (R ~ 5 000)spectra of 46 Galactic B-type supergiants is presented. Standardtechniques are adopted, viz. plane-parallel geometry and radiative andhydrostatic equilibrium. Spectroscopic atmospheric parameters (T_eff,log g & v_turb) and chemical abundances (He, C, N, O, Mg & Si)are estimated, both as a test of the validity of such an approach and inan attempt to provide consistent results for supergiants covering asignificant range of spectral types. The values of the estimatedatmospheric parameters and their dependence on the physics adopted inthe model atmospheres calculations are discussed. The absolute metalabundances are compared to those of main sequence B-type stars and, ingeneral, their chemical compositions appear to be similar. Theabundances for He, C, N & O are considered in some detail and arediscussed in the context of possible evolutionary histories for thisstellar sample. Specifically, it is found that the supergiant sample canbe subdivided into a number of evolutionarily distinct groups. The lowermass objects are predominantly chemically near-normal i.e. theirphotospheres show little or no evidence for chemical processing, whereasthe higher mass supergiants have CNO ratios which are indicative of CNand possibly NO-cycle burning. An attempt is made to quantify thedifference in nitrogen and carbon abundances between the high and lowmass targets but this is hampered by theoretical uncertainties. Thepossibilities that the most highly processed supergiants may have eitherlarger rotational velocities or have undergone mass transfer within abinary system are discussed.
|Oxygen Abundances in Late-B through F Supergiants|
A spectral-synthesis analysis was performed for twenty-six late-Bthrough F supergiants (including Cepheids) in order to determine theirphotospheric oxygen abundances from the O I 6156--8 feature, whiletaking into account the non-LTE effect, which is progressivelyT_eff-dependent from < 0.1 dex for F-type supergiants to ~ 0.4 dexfor late-B ones in terms of the non-LTE abundance correction. Theresulting oxygen abundances show a moderate underabundance relative tothe Sun ([O/H] ~ -0.3) along with a remarkably small scatter (within +/-0.1 dex) over this wide temperature range. Considering the recentevidence that the solar oxygen abundance is mildly enhanced by 0.2--0.3dex relative to that of the galactic gas which forms young stars, weconclude that the original O-composition in the atmosphere of thesesupergiants had suffered almost no appreciable alteration during theirpast evolutionary history, even though signs of significant mixing ofCN-cycle or NeNa-cycle products are evident. This excludes thepossibility of any global-mixing mechanism, such that producing asignificant reduction of oxygen due to a deep dredge-up of considerableON-processed material, whatever the details of the envelope-mixingprocess for these relatively massive stars may be.
|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.
|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.
|On the Abundances of Nitrogen and Sulfur in Late-B through F Supergiants Atmospheres|
An extensive non-LTE analysis of NI and SI lines at the spectral regionaround lambda ~ 8700Angstroms was performed for late-B through Fsupergiants in order to determine the photospheric abundances of N and Sin such massive evolved stars. It was revealed that the abundances ofnitrogen in these stars show a rather large diversity ( ~ +/- 0.4 dex)around the mean of [N/H] =~ 0.3 relative to the Sun, being roughlydivided into three groups: (i) markedly large overabundances amountingto 0.6--0.7 dex, (ii) mild N-excesses of 0.3--0.4 dex, and (iii)near-solar (or slightly subsolar) [N/H]-values. The abundances of sulfurfor F-supergiants were found to be nearly homogeneous and not muchdifferent from the solar composition ([S/H] ~ -0.2), while those for theA-type generally show a tendency of S-excess (up to +0.8 dex)systematically increasing with T_eff. There also appears a trend ofmass-dependence as well as a possibility of mutual correlation regardingthe values of [N/H] and [S/H] in those A-supergiants. It was confirmedthat the extent of the N-excess in A--F supergiants tends to depend onthat of sodium as [N/H] =~ [Na/H].
|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.
|An atlas of ultraviolet P Cygni profiles|
We have selected spectra of 232 stars from the International UltravioletExplorer (IUE) archives for inclusion in an atlas intended for varioususes but tailored especially for the study of stellar winds. The atlascovers the range in spectral types from O3 to F8. The full atlas coversthe reduced and normalized high resolution spectra from the IUE long-and short-wavelength spectrographs. Here we discuss the selection of thestars and the data reduction, and we present in velocity units theprofiles of lines formed in the stellar winds. The selected lines covera wide range of ionizations, allowing a comparison of the profiles fromdifferent ions in the wind of each star and a comparison of thedifferent wind lines as a function spectral type and luminosity. We alsopresent the basic data on the program stars to facilitate study of thedependence of wind features on stellar parameters such as luminosity,temperature, escape velocity, and v sin i. We provide an overview of thecharacteristic behavior of the wind lines in the H-R diagram. Thecomplete spectra are available in digital form through the NASAAstrophysics Data System (ADS). We offer a description of the electronicdatabase that is available through the ADS and guidelines for obtainingaccess to that database.
|Galactic B-supergiants. II - Line strengths in the visible: Evidence for evolutionary effects?|
Following the discovery by Lennon et al. (1992) of anomalously weakcarbon lines in the Galactic B-supergiants, a search was conducted forthe signatures of CNO processed material in the atmospheres of thesestars. It was found that the NII line strengths around spectral type B2correlate with luminosity, but exhibit a clear anticorrelation with theCII lines. It is suggested that this trend may be evidence for CNOprocessed material contaminating the atmospheres of the most luminousstars. The CNO processing signature was found to be most pronounced inthe more luminous supergiants, in qualitative agreement with stellarevolution calculations (provided that such stars have passed through aprevious red-supergiant phase of evolution).
|Environment Dependence of Interstellar Extinction Curves|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&A...274..439J&db_key=AST
|Groups of stars with common motion in the Galaxy. Groups of O and B stars|
|An Einstein Observatory SAO-based catalog of B-type stars|
About 4000 X-ray images obtained with the Einstein Observatory are usedto measure the 0.16-4.0 keV emission from 1545 B-type SAO stars fallingin the about 10 percent of the sky surveyed with the IPC. Seventy-fourdetected X-ray sources with B-type stars are identified, and it isestimated that no more than 15 can be misidentified. Upper limits to theX-ray emission of the remaining stars are presented. In addition tosummarizing the X-ray measurements and giving other relevant opticaldata, the present extensive catalog discusses the reduction process andanalyzes selection effects associated with both SAO catalog completenessand IPC target selection procedures. It is concluded that X-rayemission, at the level of Lx not less than 10 exp 30 ergs/s, is quitecommon in B stars of early spectral types (B0-B3), regardless ofluminosity class, but that emission, at the same level, becomes lesscommon, or nonexistent, in later B-type stars.
|Extinction law survey based on UV ANS photometry|
The paper presents an extensive survey of interstellar extinction curvesderived from the ANS photometric measurements of early type starsbelonging to our Galaxy. This survey is more extensive and deeper thanany other one, based on spectral data. The UV color excesses aredetermined with the aid of 'artificial standards', a new techniqueproposed by the authors which allows the special check of Sp/L match ofa target and the selected standard. The results indicate that extinctionlaw changes from place to place.
|Galactic B-supergiants. I - an atlas of O9-B9 supergiant spectra from 3950 A to 4950 A|
CCD spectra are presented for supergiants of spectral types O9-B9 andluminosity subclasses Ia and Ib. They cover the wavelength region fromapproximately 3950 A to 4950 A at a resolution of 0.8 A, and normallyhave a signal-to-noise in excess of 150 at 4600 A. The spectra arediscussed in respect to their classification. A number of stars showclear evidence of the 'filling in' of hydrogen lines by emission fromthe stellar wind, while HD 190603, a B1.5 Ia(+) hypergiant, exhibits anH-beta P-Cygni type line-profile. Also reported is the finding of a newnitrogen weak star, HD 13866, in the Per OB1 association which isclassified here as BC2 Ib.
|Absolute magnitudes of B emission line stars - Correlation between the luminosity excess and the effective temperature|
A new determination of the visual absolute magnitude of Be stars iscarried out. For this, a new calibration of visual absolute magnitudesof B stars of luminosity classes, V, IV, and III is first obtained froma sample of 215 stars. The absolute luminosity excess in the visual isdetermined for a sample of 49 Be stars. It is found that this excess iscorrelated with the effective temperature of the underlying stars. Awell defined correlation between this excess and the emission in thefirst two Balmer lines is established. From these results, using asimple model of circumstellar envelope, it is inferred that the zones ofthe circumstellar envelope contributing to the emission in the continuumand in the lines have to be rather small. It is also deduced that theemission measure of the envelope is correlated with the temperature ofthe central star and that the irregular photometric variations of Bestars are an envelope-opacity phenomenon.
|IUE observations of mass-loss spectral features in B5-B9 supergiants|
A survey of IUE spectra is presented for supergiants of spectral classB5-B9 illustrating the behavior of line profiles associated withmass-loss effects. The main purpose of this survey is to better identifythe spectral mass-loss features which occur in such stars in order topresent a clearer observational picture of the nature and the timescaleof their variability. Time varying 'narrow' or 'discrete absorptioncomponents' (DAC) are detected across the full spectral class range butfor the Ia supergiants only. Significant variations in the wind C IV andSi IV profiles are observed corresponding to different mass-lossepisodes. The line strengths and the edge velocities of the windprofiles in the higher ionization ions and their time variability tendto decrease towards later spectral type. However, details of systematictrends with effective temperature are obscured somewhat by the scale ofvariability which is observed for a given star.
|Third preliminary catalogue of stars observed with the photoelectric astrolabe of the Beijing Astronomical Observatory.|
|A list of MK standard stars|
|Groups of stars with common motion in the Galaxy - Groups of B stars of luminosity classes I and II and their comparison with groups of long-period Cepheids and open clusters|
In a sample of 93 stars of luminosity classes I and II, ten groups withcommon motion in space are isolated. The reality of five groups isestablished by numerical experiment. A comparison is made with groups oflong-period Cepheids and open clusters. Regularities in the distributionof groups of different objects in space are found. The reality of therotation of a star aggregate consisting of three Cepheid groups isestablished.
|H-alpha as a tracer of mass loss from OB stars|
This paper investigates the use of the H-alpha emission from stellarwinds of OB stars to determine the stellar mass-loss rate. The power inH-alpha emitted by the wind can be parameterized in terms of thetemperature and the density field of the wind. A simple expression isderived which relates the observed H-alpha luminosity to the stellarmass-loss rate, the stellar radius, the velocity law, and the stellareffective temperature. This expression is calibrated for the influenceof the velocity law using a sample of Galactic OB stars with UVmass-loss rates. Consequently, the results depend on the validity of theUV rates. The derived velocity law for O stars turns out to be inagreement with the radiation-pressure-driven wind theory. There isevidence for a dependence of the velocity-law gradient on spectral type.The results for B stars, however, are more uncertain due to thedependence on the adopted mass accretion rate/L relation. Application ofthe calibrated H-alpha luminosity/mass-loss rate relation to a sample of149 galactic OB stars shows that mass accretion rate can be reliablydetermined from H-alpha. Due to the moderate amount of observing timerequired to derive mass accretion rate from H-alpha, this method may beapplied successfully to investigate mass-loss effects in extra-Galacticstars.
|Atlas of the wavelength dependence of ultraviolet extinction in the Galaxy|
The paper presents a collection of 115 extinction curves derived fromlow-dispersion IUE spectra. The spectra have been reduced with the useof techniques designed to reduce the effects of random noise and theinfluence of residual spectral features due to classification mismatch.The magnitudes of other instrumental and interpretational uncertaintiesare estimated. The extinction curves are presented with normalization toE(B-V) = 1 and the FUV portion (below 170 nm) is also shown for E(13-17)= 1. The atlas includes examples of extinction originating in thediffuse medium and several major nebulae and dense clouds.
|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.
|Small Magellanic Cloud: H-gamma-line equivalent widths and luminosity classes of the brightest blue star members|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1987A&AS...69..421A&db_key=AST
|Observations of interstellar diffuse absorption band at 4430 A|
Observations of the interstellar diffuse absorption band at 4430 A for800 O and B stars in Neckel's (1967) catalog are being carried out, and482 spectra obtained up to September 1983 have been reduced. It isconfirmed that the strength of the interstellar diffuse absorption bandat 4430 A does not simply relate to the abundance of interstellar grainson the line of sight. The relation between the color excess E(B-V) andthe equivalent width of the band to the direction of l = 130-140 deg andb = -5 to +5 deg shows that some parameter(s) other than E(B-V) is (are)needed to understand the cause of this band.
|Interstellar lithium - Differential depletion in diffuse clouds|
Echelle-CCD observations of interstellar Li I (6708-A) have yieldeddetections toward seven stars and limits toward 15 others. Examinationof all existing data on interstellar Li absorption reveals littlevariations in the Li/K abundance ratio, but significant variation in theLi/Na ratio. Individual depletion values derived from lines of the traceneutral atoms Li, C, Na, and K correlate with one another and withelectron density. These elements exhibit differential depletion in thedensest, most shielded regions of diffuse clouds, with Li and K showinga smaller range of variation than C or Na. Considered as diagnostics ofthe grain-mantle accretion process, the observed correlations yieldratios of the effective sticking probabilities for the different atoms.The expectation that N and K should behave similarly then leads to theconclusion that the atoms accrete as ions rather than as neutrals. Theresulting effective sticking coefficient for C is slightly smaller thanfor Na and K; that for Li must be several times smaller. Thecorrelations further suggest that the background depletions for Li and Kmay be about one-half those for Na and C, and that C depletes roughly asn to the -2/3, where n is the density of H nuclei. The extremedepletions and low H2 fraction in the Rho Oph cloud imply a low H2formation rate, significantly smaller than 10 to the -17th cu cm.
|Catalog of O-B stars observed with Tokyo Meridian Circle|
A catalog of the O-B stars, selected from 'Blaauw-Parenago' list andRubin's catalog, has been compiled on the FK4 system by the observationsmade with Gautier 8-inch Meridian Circle at the Tokyo AstronomicalObservatory during the period, 1971 to 1979. It contains 1059 stars andwas compiled for the future establishment of high precision propermotions of O-B stars.
|The local system of early type stars - Spatial extent and kinematics|
Published uvby and H-beta photometric data and proper motions arecompiled and analyzed to characterize the structure and kinematics ofthe bright early-type O-A0 stars in the solar vicinity, with a focus onthe Gould belt. The selection and calibration techniques are explained,and the data are presented in extensive tables and graphs and discussedin detail. The Gould belt stars of age less than 20 Myr are shown togive belt inclination 19 deg to the Galactic plane and node-lineorientation in the direction of Galactic rotation, while the symmetricaldistribution about the Galactic plane and kinematic properties (purecircular differential rotation) of the belt stars over 60 Myr oldresemble those of fainter nonbelt stars of all ages. The unresolveddiscrepancy between the expansion observed in the youngest nearby starsand the predictions of simple models of expansion from a point isattributed to the inhomogeneous distribution of interstellar matter.
Submit a new link
Member of following groups:
Observation and Astrometry data
|Proper motion RA:||-2.3|
|Proper motion Dec:||-1.7|
Catalogs and designations: