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.
|
Simultaneous photometric and spectroscopic monitoring of rapid variations of the Be star η Centauri.
Results of the simultaneous monitoring of line-profile and light andcolour variations of the bright southern Be star ηCen in May-June1992 are reported. The new data were analyzed along with numerousearlier b and uvby observations of the star, secured between 1987 and1991. The brightness of ηCen varies on three distinct time scalesbut only rapid variations on a time scale of hours to days are analyzedhere. They can be described as a superposition of a periodic componentwith period 0.6424241d, which is secularly stable over the wholesix-year interval covered by our data, and systematic but obviouslyaperiodic cycle-to-cycle disturbances. The 0.6424-d light curve isslightly non-sinusoidal (light minima occur 0.64^P^ after light maxima)and has an average peak-to-peak amplitude of 0.05mag in y, b and v andabout 0.10mag in u. The u-b and 1 indices also vary with the sameperiod, with full amplitudes of 0.04mag and 0.03mag, respectively, whilethe variations of b-y and .1mag - if present - are within 0.01mag only.During light maximum, the star is bluest in u-b. The radial velocity ofSi III 455.26nm as measured in the outer wings of the profile exhibits anearly sinusoidal variation with the 0.6424-d period and definitivelyexcludes the triple-wave photometric period of 1.927d consideredearlier. For variations of other line-profile parameters of the Si III455.26 nm line, the most significant periods differ by up to +/-5% fromthe 0.6424-d period. More extended spectroscopic material will be neededto confirm our preliminary conclusion that this disparity is ofstochastic nature only and that the entire line-profile variability maybe reconciled with the photometric period. The exactly simultaneousmonitoring shows that radial velocity, first moment, equivalent width,and line depth of the Si III 455.26nm line increase when the star isgetting brighter and bluer. Very pronounced higher-order line-profilevariations of the Si III line were also detected. They have thecharacter of apparent absorption or emission bumps, which move acrossthe line profile from blue to red. Most of them disappear close to theline center. The analysis of their radial velocities leads to asuper-period, which is close to the photometric one. Occurrence andstrength of the bumps also seem to follow the same period. The light,colour, radial-velocity and equivalent-width variations can only be dueto the low-order line profile variations or duplicity. The observedradial-velocity amplitude seems to be larger than expected for therotational modulation and nonradial pulsation models. Theequivalent-width variation cannot be understood unless a phase-dependentmicroturbulent velocity is assumed in both models. Available data cannotalso exclude a model of a contact binary with 0.6-day orbital period.
|
Four Colour Photometry of Eclipsing Binaries - Part Thirty-Five - Lightcurves of Gg-Lupi - Young Metal-Deficient B-Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&AS..101..563C&db_key=AST
|
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.
|
Intensive photometry of southern Be variables. I - Winter objects
Results are presented from an intensive photometric campaign on somebright southern Be stars to search for periodic light variations. Inorder to obtain good phase coverage, observations were conducted fromtwo sites with different longitude: ESO and SAAO. Most of the starsobserved are indeed variable with periods close to one day. Results forwinter objects are given.
|
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.
|
A catalog of ultraviolet interstellar extinction excesses for 1415 stars
Ultraviolet interstellar extinction excesses are presented for 1415stars with spectral types B7 and earlier. The excesses with respect to Vare derived from Astronomical Netherlands Satellite (ANS) 5-channel UVphotometry at central wavelengths of approximately 1550, 1800, 2500, and3300 A. A measure of the excess extinction in the 2200-A extinction bumpis also given. The data are valuable for investigating the systematicsof peculiar interstellar extinction and for studying the character of UVinterstellar extinction in the general direction of stars for which theextinction-curve shape is unknown.
|
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.
|
Element depletions in interstellar gas. II - The density-dependence of calcium and sodium depletions
The behavior of Ca and Na depletions in interstellar gas is studied inview of complementary, high resolution optical and UV spectra for ninestars in the same region of sky. The optical absorption lines of Ca IIand Na I are analyzed to determine their column densities in eachline-of-sight, and the UV data are used to estimate H column densitiesand to perform ionization balance calculations from which thecontributions to Ca and Na abundances from unobserved ion stages can bededuced. The resultant element depletions relative to solar abundancesare compared with estimates of the average interstellar gas density indifferent lines-of-sight. The depletion of Ca is a strong function ofpresent interstellar medium densities, while Na appears to be depletedby a constant factor of about 4 over the range of densities sampled.Shock sputtering of grains plays an important role in determiningelement depletions, even in low velocity interstellar gas.
|
Search for Beta Cephei stars south of declination -20 deg. II - Photometric and spectrographic observations of early B giants and subgiants - Winter objects
Results of the second part of a program begun in 1975 (Jerzykiewicz andSterken, 1977) are presented. Out of 39 Beta Cephei candidates observedphotometrically, seven turned out to vary with the b ranges exceeding0.020 m, while 21 have been found constant to within 0.010 m or better.For the 56 comparison stars these numbers are 6 and 25, respectively.From spectrographic observations one of the candidates, HD 129557 = HR5488 (B2 III), iis found to be a Beta Cephei variable with a period of0.135 d and the 2 K amplitude of 18.4 km/s. A comparison of the resultsof this program with other recent photometric searches for Beta Cepheivariables shows good agreement in most cases. There are severaldiscrepant stars, however. These are discussed in some detail. Aconclusion emerges that in the low temperature extension of the BetaCephei region, if such an extension exists at all, on-and-off typepulsations occur.
|
Element depletions in interstellar gas
High resolution IUE observations were analyzed to derive elementdepletions in low velocity interstellar gas toward several stars in thesame region of sky. The results were combined with previous observationsto determine how the level of depletion of a given element depends onpresent densities in the interstellar medium. The density dependence ofdepletions is found to vary from element to element; this variation isdiscussed in light of depletion models. Results indicate that sputteringof grains in interstellar shocks is important in determining elementdepletions.
|
A study of element depletions in interstellar gas
Optical and ultraviolet studies have shown that most elements in the gasphase of the interstellar medium are underabundant relative to the solarcomposition. The missing gas atoms are assumed to be contained ininterstellar grains. The study of the depletion of interstellar elementsin the gas phase provides, in this connection, a means for studying thecomposition of interstellar dust and possibly its formation/destructionmechanisms. The present investigation is concerned with ultravioletobservations of interstellar gas in the lines-of-sight toward sevenstars. The high resolution ultraviolet spectra of the seven stars wereobtained with the International Ultraviolet Explorer (IUE) satellite.The results of the investigation indicate that, at least for certainelements, the level of depletion depends on present densities in theinterstellar medium. The implications of this conclusion are examined.
|
The interstellar 2200 A band - A catalogue of equivalent widths
Not Available
|
Four-colour and H-beta photometry for early type stars in three southern galactic regions
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&AS...41...85L&db_key=AST
|
A search for Beta Cephei stars. III - Photometric studies of southern B-type stars
The result of a photometric search for Beta Cephei stars among a groupof 37 southern B-type stars is presented. Beside two new Beta Cepheistars, one eclipsing binary, one helium-weak variable, and ten slowvariables were found.
|
Space velocities and ages of nearby early-type stars
Photometric distances and space velocities have been calculated for 458B0-A0 stars with apparent magnitudes not exceeding 6.5. UsingStromgren's ubvy-beta photometry the effective temperature and theposition in bolometric magnitude over the zero-age main sequence of thestars were derived. These quantities were used to obtain age and massfor 423 of the stars by interpolation in the models of stellar evolutionfor the chemical composition (X Z) = (0.7, 0.03). A relation forderiving interstellar reddening for normal stars in the intermediategroup is given.
|
Structure and age of the local association /Pleiades group/
Intermediate-band indices are used to derive luminosities for some 500early-type stars with well-determined proper motions and radialvelocities. Space motion vectors and galactic coordinates are computedfor the stars considered. It is found that the local association membersare mainly concentrated in the Sco-Cen region in the Southern Hemisphereand the Cas-Tau region in the north.
|
Carbon and iron abundances for twenty F and G type stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974A&A....36..191H&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
|
Four-color and H-beta photometry for bright B-type stars in the southern hemisphere.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971AJ.....76..621C&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
|
Radial velocities of 200 southern B stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1965MNRAS.130..281B&db_key=AST
|
A Survey of Southern Be Stars
Not Available
|
