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|An Extended FUSE Survey of Diffuse O VI Emission in the Interstellar Medium|
We present a survey of diffuse O VI emission in the interstellar medium(ISM) obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE).Spanning 5.5 yr of FUSE observations, from launch through 2004 December,our data set consists of 2925 exposures along 183 sight lines, includingall of those with previously published O VI detections. The data wereprocessed using an implementation of CalFUSE version 3.1 modified tooptimize the signal-to-noise ratio and velocity scale of spectra from anaperture-filling source. Of our 183 sight lines, 73 show O VIλ1032 emission, 29 at >3 σ significance. Six of the 3σ features have velocities |vLSR|>120 kms-1, while the others have |vLSR|<=50 kms-1. Measured intensities range from 1800 to 9100 LU (lineunit; 1 photon cm-2 s-1 sr-1), with amedian of 3300 LU. Combining our results with published O VI absorptiondata, we find that an O VI-bearing interface in the local ISM yields anelectron density ne=0.2-0.3 cm-3 and a path lengthof 0.1 pc, while O VI-emitting regions associated with high-velocityclouds in the Galactic halo have densities an order of magnitude lowerand path lengths 2 orders of magnitude longer. Although the O VIintensities along these sight lines are similar, the emission isproduced by gas with very different properties.Based on observations made with the NASA-CNES-CSA Far UltravioletSpectroscopic Explorer. FUSE is operated for NASA by Johns HopkinsUniversity under NASA contract NAS5-32985.
|Two- and Three-Dimensional Hydrodynamical Simulations of Mass Transfer in Semidetached Binaries with Explicit Radiative Cooling and Self-Absorption in Their Gaseous Envelopes|
We have modeled the mass transfer in three Algol-type binaries usingtwo-and three-dimensional numerical hydrodynamical techniques. Radiativecooling and absorption in the envelopes surrounding the components ofthe close binaries are explicitly taken into account. The resultingenvelope temperatures are consistent with those observed. We derivedthese temperatures by considering the energy balance in the moving gas,including heating due to the numerical viscosity that is inherent to thesimulations and radiative cooling. The radiative cooling was calculatedassuming an optically thin plasma in a state of ionization balance.Taking into account both of these processes yielded temperatures of 400030 000 K in the disk around the accreting primary and in the commonenvelope surrounding the close binary. Our computations also indicatethat the envelope morphology is not sensitive to the radiative-coolingmodel used.
|Phosphorus in the diffuse interstellar medium|
We present FUSE and HST/STIS measurements of the P ii column densitytoward Galactic stars. We analyzed P ii through the profile fitting ofthe unsaturated λ1125 and λ1533 lines and derived columndensities integrated along the sightlines as well as in individualresolved components. We find that phosphorus is not depleted along thosesightlines sampling the diffuse neutral gas. We also investigate thecorrelation existing between P ii and O i column densities and find thatthere is no differential depletion between these two specie.Furthermore, the ratio N(P ii)/N(O i) is consistent with the solar P/Ovalue, implying that P ii and O i coexist in the same gaseous phase andare likely to evolve in parallel. We argue that phosphorus, as traced byP ii, is an excellent neutral oxygen tracer in various physicalenvironments, except when ionization corrections are a significantissue. Thus, P ii lines (observable with FUSE, HST/STIS, or withVLT/UVES for the QSO sightlines) are particularly useful as a proxy forO i lines when these are saturated or blended.
|Two-Dimensional Hydrodynamical Modeling of Mass Transfer in Semidetached Binaries with Asynchronously Rotating Components|
We have modeled the mass transfer in the three semidetached binaries UCep, RZ Sct, and V373 Cas taking into account radiative cooling bothimplicitly and explicitly. The systems have asynchronously rotatingcomponents and high mass-transfer rates of the order of 10-6 Mȯ/yr; they are undergoing various stages of their evolution. Anaccreting star rotates asynchronously if added angular momentum isredistributed over the entire star over a time that exceeds thesynchronization time. Calculations have indicated that, in the modelconsidered, mass transfer through the point L1 is unable todesynchronize the donor star. The formation of an accretion disk andouter envelope depends on the component-mass ratio of the binary. Ifthis ratio is of the order of unity, the flow makes a direct impact withthe atmosphere of the accreting star, resulting in the formation of asmall accretion disk and a relatively dense outer envelope. This is trueof the disks in U Cep and V373 Cas. When the component-mass ratiosubstantially exceeds unity (the case in RZ Sct), the flow forms alarge, dense accretion disk and less dense outer envelope. Taking intoaccount radiative cooling both implicitly and explicitly, we show that aseries of shocks forms in the envelopes of these systems.
|Oxygen Gas-Phase Abundance Revisited|
We present new measurements of the interstellar gas-phase oxygenabundance along the sight lines toward 19 early-type Galactic stars atan average distance of 2.6 kpc. We derive O I column densities fromHubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS)observations of the weak 1355 Å intersystem transition. We derivetotal hydrogen column densities [N(HI)+2N(H2)] using HST/STISobservations of Lyα and Far Ultraviolet Spectroscopic Explorer(FUSE) observations of molecular hydrogen. The molecular hydrogencontent of these sight lines ranges fromf(H2)=2N(H2)/[N(HI)+2N(H2)]=0.03 to0.47. The average of6.3×1021 cm-2 mag-1 with astandard deviation of 15% is consistent with previous surveys. The meanoxygen abundance along these sight lines, which probe a wide range ofGalactic environments in the distant interstellar medium, is106 (O/H)gas=408+/-13 (1 σ in the mean). Wesee no evidence for decreasing gas-phase oxygen abundance withincreasing molecular hydrogen fraction, and the relative constancy of(O/H)gas suggests that the component of dust containing theoxygen is not readily destroyed. We estimate that, if 60% of the dustgrains are resilient against destruction by shocks, the distantinterstellar total oxygen abundance can be reconciliated with the solarvalue derived from the most recent measurements of 106(O/H)gassolar=517+/-58 (1 σ). We note thatthe smaller oxygen abundances derived for the interstellar gas within500 pc or from nearby B star surveys are consistent with a localelemental deficit.
|Far Ultraviolet Spectroscopic Explorer Snapshot Survey of O VI Variability in the Winds of 66 OB-Type Stars|
We have used the Far Ultraviolet Spectroscopic Explorer to conduct asnapshot survey of O VI variability in the winds of 66 OB-type stars inthe Galaxy and the Magellanic Clouds. These time series consist of twoor three observations separated by intervals ranging from a few days toseveral months. Although these time series provide the bare minimum ofinformation required to detect variations, this survey demonstrates thatthe O VI doublet in the winds of OB-type stars is variable on variousscales in both time and velocity. For spectral types from O3 to B1, 64%vary in time. At spectral types later than B1, no wind variability isobserved. In view of the limitations of this survey, this fractionrepresents a lower limit on the true incidence of variability in the OVI wind lines, which is very common and probably ubiquitous. Incontrast, for S IV and P V, only a small percentage of the whole sampleshows wind variations, although this may be principally due to selectioneffects. The observed variations extend over several hundreds ofkilometers per second of the wind profile and can be strong. The widthover which the wind O VI profile varies is only weakly correlated withthe terminal velocity (v&infy;), but a significantcorrelation (close to a 1:1 relationship) is derived between the maximumvelocity of the variation and v&infy;. High-velocity O VIwind absorption features (possibly related to the discrete absorptioncomponents seen in other wind lines) are also observed in 46% of thecases for spectral types from O3 to B0.5. These features are variable,but the nature of their propagation cannot be determined from thissurvey. If X-rays can produce sufficient O VI by Auger ionization of OIV and the X-rays originate from strong shocks in the wind, this studysuggests that stronger shocks occur more frequently nearv&infy;, causing an enhancement of O VI nearv&infy;.
|The total-to-selective extinction ratio determined from near IR photometry of OB stars|
The paper presents an extensive list of the total to selectiveextinction ratios R calculated from the infrared magnitudes of 597 O andB stars using the extrapolation method. The IR magnitudes of these starswere taken from the literature. The IR colour excesses are determinedwith the aid of "artificial standards" - Wegner (1994). The individualand mean values of total to selective extinction ratios R differ in mostcases from the average value R=3.10 +/-0.05 - Wegner (1993) in differentOB associations. The relation between total to selective extinctionratios R determined in this paper and those calculated using the "methodof variable extinction" and the Cardelli et al. (1989) formulae isdiscussed. The R values presented in this paper can be used to determineindividual absolute magnitudes of reddened OB stars with knowntrigonometric parallaxes.
|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.
|The Distribution of Thermal Pressures in the Interstellar Medium from a Survey of C I Fine-Structure Excitation|
We used the Space Telescope Imaging Spectrograph (STIS) with itssmallest entrance aperture (0.03" wide slit) and highest resolutionechelle gratings (E140H and E230H) to record the interstellar absorptionfeatures for 10 different multiplets of neutral carbon at a resolvingpower of λ/Δλ=200,000 in the UV spectra of 21early-type stars. Our objective was to measure the amount of C I in eachof its three fine-structure levels of the ground electronic state, sothat we could determine the thermal pressures in the absorbing gas andhow much they vary in different regions. Our observations areprincipally along directions out to several kiloparsecs in the Galacticplane near longitudes l=120deg and 300°, with the moredistant stars penetrating nearby portions of the Perseus andSagittarius-Carina arms of the Galaxy. We devised a special analysistechnique to decipher the overlapping absorption features in thedifferent multiplets, each with different arrangements of the closelyspaced transitions. In order to derive internally consistent results forall multiplets, we found that we had to modify the relative transitionf-values in a way that made generally weak transitions stronger thanamounts indicated in the current literature. We compared our measuredrelative populations of the excited fine-structure levels to thoseexpected from equilibria calculated with collisional rate constants forvarious densities, temperatures, and compositions. The median thermalpressure for our entire sample was p/k=2240 cm-3 K, orslightly higher if the representative temperatures of the material aremuch above or below a most favorable temperature of 40 K for theexcitation of the first excited level at a given pressure. For gas thatis moving outside the range of radial velocities permitted bydifferential Galactic rotation between us and the targets, about 15% ofthe C I indicates a thermal pressure p/k>5000 cm-3 K. Forgas within the allowed velocities, this fraction is only 1.5%. Thiscontrast reveals a relationship between pressure enhancements and thekinematics of the gas. Regardless of velocity, we usually can registerthe presence of a very small proportion of the gas that seems to be atp/k>~105 cm-3 K. We interpret these ubiquitouswisps of high-pressure material to arise either from small-scale densityenhancements created by converging flows in a turbulent medium or fromwarm turbulent boundary layers on the surfaces of dense clouds movingthrough an intercloud medium. For turbulent compression, our C Iexcitations indicate that the barytropic indexγeff>~0.90 must apply if the unperturbed gas startsout with representative densities and temperatures n=10 cm-3and T=100 K. This value for γeff is larger than thatexpected for interstellar material that remains in thermal equilibriumafter it is compressed from the same initial n and T. However, ifregions of enhanced pressure reach a size smaller than ~0.01 pc, thedynamical time starts to become shorter than the cooling time, andγeff should start to approach the adiabatic valuecp/cv=5/3. Some of the excited C I may arise fromthe target stars' H II regions or by the effects of optical pumping fromthe submillimeter line radiation emitted by them. We argue that thesecontributions are small, and our comparisons of the velocities ofstrongly excited C I to those of excited Si II seem to support thisoutlook. For six stars in the survey, absorption features frominterstellar excited O I could be detected at velocities slightlyshifted from the persistent features of telluric origin. These O I* andO I** features were especially strong in the spectra of HD 93843 and HD210839, the same stars that show exceptionally large C I excitations. Inappendices of this paper, we present evidence that (1) the wavelengthresolving power of STIS in the E14OH mode is indeed about 200,000, and(2) the telluric O I* and O I** features exhibit some evidence formacroscopic motions, since their broadenings are in excess of thatexpected for thermal Doppler broadening at an exospheric temperatureT=1000 K. Based on observations with the NASA/ESA Hubble Space Telescopeobtained at the Space Telescope Science Institute, which is operated bythe Association of Universities for Research in Astronomy, Inc., underNASA contract NAS 5-26555.
|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
|Apsidal Motion in Double Stars. I. Catalog|
A catalog of 128 double stars with measured periods of apsidal motion iscompiled. Besides the apsidal periods, the orbital elements of binariesand physical parameters of components (masses, radii, effectivetemperatures, surface gravities) are given. The agreement of the apsidalperiods found by various authors is discussed.
|Discovery of the variable phase-locked polarization in LZ Cephei|
The early-type non-eclipsing binary LZ Cep has been observed with theUBVRI polarimeter during 25 nights in 1996-1997. A variable phase-lockedlinear polarization has been found. The principal Fourier components ofthe observed variations are the second harmonics of the orbital period.The most probable explanation of this variability is reflection of theradiation from each component of the binary off the facing hemisphere ofits companion. We have constructed a simple numerical model of thereflection process which is capable of reproducing the amplitude andphase dependence of the polarized light-curve.
|UBVI photometry and polarimetry of V373 Cas.|
|The binary system V373 Cas: orbital elements, parameters of the components, and helium abundance|
CCD spectra with high resolution and large signal-to-noise ratio areused to study the binary system V373 Cas, which includes two early Bstars, and is apparently undergoing a very early phase of mass exchangebetween the components. The new radial velocity measurements made itpossible to improve the system's orbital elements and to refine the massestimates for the components: M_orb = 18.6 +/- 2.4 M for the primary(star A) and 14.2 +/- 1.9M_solar for the secondary (star B). Aself-consistent method for estimation of the effective temperature andgravitational acceleration yields T_eff = 23,200 +/- 600 K and lg g= 3.0+/- 0.2 for component A and T_eff = 26,800 +/- 1500 K and lg g = 3.5 +/-0.2 for component B. These parameters correspond to the spectral typesB0.5-B1 (II-Ib) for A and B0.5 III for B. The helium abundance isenhanced in the atmospheres of both components: He/H = 0.23 +/- 0.03 and0.18 +/- 0.02 for A and B, respectively. This helium abundance excessconfirms that He/H depends on age, and is consistent with the fact thatboth the components of V373 Cas are near the end of the main sequencestage. The magnesium abundance for the primary is close to the solarvalue, suggesting that its metallicity may be normal. The rotationvelocities sin i = 130 +/- 10 km/s (A) and 60 +/- 5 km/s (B) are derivedfrom the He I lines. These confirm the conclusion of Hill and Fisherthat the rotation of the components in their orbital motion isasynchronous. The masses M_ev estimated using evolutionary tracks areoverestimated by 34% for the both components, compared to the moreaccurate values M_orb determined from the orbit analysis. This is thelargest known discrepancy between M_ev and M_orb for a binary system ofthis type. The age of the system is 7-8 million years.
|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.
|Long-term variability of the emission spectrum of the Be star beta Cephei.|
|Cross-correlation characteristics of OB stars from IUE spectroscopy|
We present a catalogue of homogeneous measures of the linewidthparameter, v_esin i, for 373 O-type stars and early B supergiants(including the separate components of 25 binary and three triplesystems), produced by cross-correlating high-resolution,short-wavelength IUE spectra against a `template' spectrum of tauSco. Wealso tabulate terminal velocities. There are no O supergiants in oursample with v_esin i<65 km s^-1, and only one supergiant earlier thanB5 has v_esin i<50 km s^-1, confirming that an important linebroadening mechanism in addition to rotation must be present in theseobjects. A calibration of the area under the cross-correlation peakagainst spectral type is used to obtain estimates of continuum intensityratios of the components in 28 spectroscopically binary or multiplesystems. At least seven SB2 systems show evidence for the `Struve-Sahadeeffect', a systematic variation in relative line strength as a functionof orbital phase. The stellar wind profiles of the most rapid rotator inour sample, the O9III:n* star HD 191423 (v_esin i=436km s^-1), show itto have a `wind-compressed disc' similar to that of HD 93521; this starand other rapid rotators are good candidates for studies of non-radialpulsation.
|Bow Shocks Around Runaway Stars.III.The High Resolution Maps|
In a recent survey for bow shock structures around OB runaway starsusing the ISSA/IRAS archival data and excess maps at 60 \mum, 58candidates were found. These objects are surrounded by extended infraredemission at 60 \mum, characteristic of warm dust heated by ultravioletphotons, a signature of wind bow shocks. High resolution IRAS (HiRes)images have been produced for these 58 objects and some of thosespatially resolved are presented in this study. The images were used todistinguish between multiple confused IR sources, possible artifacts andunambiguous bow shocks, as the sources of the extended 60 \mum emission.Six new bow shocks have been identified using this method, and threehave been rejected. Twenty two of the targets, however, remain spatiallyunresolved even at the nominal HiRes resolution of ~ 1arcmin . For thelarger and better defined bow shocks some internal substructure isdiscernible. The length of these features suggest that they arise as theresult of a subtle dynamical instability. It can not be ruled out,however, that some of the bow shock morphology could be imprinted by thesurrounding medium.
|A Catalogue of Correlations Between Eclipsing Binaries and Other Categories of Double Stars|
Among the 9110 stars in The Bright Star Catalogue, there are 225eclipsing or ellipsoidal variables. A search has been made for these incatalogues of spectroscopic binaries, visual double or multiple stars,speckle interferometry, occulation binaries, and galatic clusters. Themajority of the photometric binaries are also members of groups ofhigher multiplicity. The variables are in systems ranging from one to 91stars, five on the average. 199 are either spectroscopic binaries (SB)or stars with variable radial velocity, with orbital periods known for160. Photometric periods are lacking for 48 while SB periods areavailable for 23 of these. Observers with photoelectric equipment areencouraged to plan observations to test if the SB periods are consistentwith photometric data. Observers are likewise encouraged to examinethose stars for which the photometric and SB periods appear to beinconsistent. Parallaxes are available for 86 of the stars, 41 of themindicating distances nearer than 50 parsecs.
|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.
|Eclipsing binaries as IRAS sources.|
In a systematic search we looked for coincidences in the positions ofeclipsing binaries and IRAS point sources as evidence of a physicalassociation. In a detailed discussion of the available optical andinfrared data combined with model calculations, we show that 50-75% ofthe coincidences between eclipsing binaries and IRAS sources are real.We discuss a subsample of 44 stars in some detail and surveyed thevicinity of them on POSS and SRC/ESO atlases for possible opticalcounterparts and present identification maps. In the cases of BS Sco andV 718 Sco the infrared radiation may come from an accretion disk.
|Spectroscopic and Polarimetric Observations of the Nova Cassiopeiae 1993|
|The Discovery of H-alpha Emission in V373 Cas|
|Observations of Variable Stars with the R-Coronae Phenomenon and Other Unique Objects|
|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 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.
|Speckle observations of visual and spectroscopic binaries. V.|
|Speckle observations of visual and spectroscopic binaries. IV|
This is the fourth paper of this series giving results of speckleobservations for 22 visual and 161 spectroscopic binaries. Theobservation was carried out by using the 212 cm telescope of San PedroMartir Observatory in Mexico on 7 nights from July 20 to July 26, 1991.We obtained fringes in power spectra of 19 visual and 11 spectroscopicbinaries (6 newly resolved ones) with angular separation larger than0.06 arcsec. We introduced a new ICCD TV camera in this observation, andwere able to achieve the diffraction-limit resolution of the 212 cmtelescope.
|Speckle observations of visual and spectroscopic binaries. III|
This is the third paper of this series giving results of speckleobservations carried out for seven visual and 119 spectroscopic binariesat seven nights from May 20 to May 27, 1989, and for 30 visual and 272spectroscopic binaries at 12 nights from June 11 to June 15, and fromAugust 28 to September 3, 1990, using the 212-cm telescope at San PedroMartir Observatory in Mexico. Fringes in the lower spectrum of 31 visualand spectroscopic binaries with angular separation larger than 21 arcsecare obtained. Additionally to two spectroscopic binaries, HD41116 andHD206901, named in the second paper of this series, six spectroscopicbinaries are found each of which has the third component starsurrounding two stars of spectroscopic binary having periodic variationof radial velocity.
|Groups of stars with common motion in the Galaxy. Groups of O and B stars|