|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.
|The CHARA Catalog of Orbital Elements of Spectroscopic Binary Stars|
Optical interferometry is entering a new age, with several ground-basedlong-baseline observatories now making observations of unprecedentedresolution. Interferometers bring a new level of resolution to bear onspectroscopic binaries, enabling the full extraction of the physicalparameters for the component stars with high accuracy. In the case ofdouble-lined systems, a geometrically determined orbital parallaxbecomes available as well. The first step in preparing to observespectroscopic binaries is to list them, which has not been done sincethe 1989 publication of the Eighth Catalogue of the Orbital Elements ofSpectroscopic Binaries by Batten et al. We present a new catalog withroughly half again as many listings as the Eighth Catalogue. Angularseparation predictions are made for each catalog entry. The numbers ofspectroscopic binaries available for study as a function of severalimportant observational parameters are explored, and in particular, thenumber of spectroscopic binaries as a function of expected separation isdiscussed.
|The mass ratio distribution of B-type visual binaries in the Sco OB2 association|
A sample of 115 B-type stars in the Sco OB2 association is examined forexistence of visual companions in the J and K_s bands, using the ADONISnear-infrared adaptive optics system and coronograph. Practically allthe components in the separation range 0farcs3 -6farcs4 (45-900 AU) andmagnitudes down to K = 16 were detected. The K and J - K photometry ofthe primaries and differential photometry and astrometry of the 96secondaries are presented. Ten secondaries are new physical components,as inferred from the photometric and statistical criteria, while therest of the newly detected objects are faint background stars. After asmall correction for detection incompleteness and a conversion of thefluxes into masses, an unbiased distribution of the components massratio q was derived. The power law f(q)~ q-0.5 fits theobservations well, whereas a q-1.8 distribution, whichcorresponds to a random pairing of stars, is rejected. The companionstar fraction is 0.20+/-0.04 per decade of separation which iscomparable to the highest measured binary fraction among low-mass PMSstars and ~ 1.6 times higher than the binary fraction of low-mass dwarfsin the solar neighborhood and in open clusters in the same separationrange. Based on observations collected at the European SouthernObservatory, La Silla, Chile (ESO programme 65.H-0179). Tables 1, 3 andthe full version of Table 2 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (188.8.131.52) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/382/92
|Binary Star Observations in Selected Instants of Good Seeing|
Video recordings of images of binary stars at the focus of a 0.36mtelescope have been used to select images recorded in instants of goodseeing. The selected images have been analysed to give separations andposition angles for the binary systems which are in good agreement withvalues predicted from previous observations. In these exploratoryobservations it has been shown that separations of 0.9 arcseconds can bemeasured with an accuracy of ~2% and position angles to ~1-2 degreeswhen the average seeing was ~1.3 arcseconds. These observationsdemonstrated that the diffraction limit of the telescope could bereached when the seeing was a factor of 2-3 greater than it. A binarywith three magnitudes difference in the brightness of its components hasbeen measured with comparable accuracy although difficulties areanticipated for binaries with components closer than ~2 arcseconds withthis magnitude difference. The limiting magnitude is determined by theneed to limit exposure times of individual frames to be comparable withor less than the atmospheric coherence time.
|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 (184.108.40.206) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
|The proper motions of fundamental stars. I. 1535 stars from the Basic FK5|
A direct combination of the positions given in the HIPPARCOS cataloguewith astrometric ground-based catalogues having epochs later than 1939allows us to obtain new proper motions for the 1535 stars of the BasicFK5. The results are presented as the catalogue Proper Motions ofFundamental Stars (PMFS), Part I. The median precision of the propermotions is 0.5 mas/year for mu alpha cos delta and 0.7mas/year for mu delta . The non-linear motions of thephotocentres of a few hundred astrometric binaries are separated intotheir linear and elliptic motions. Since the PMFS proper motions do notinclude the information given by the proper motions from othercatalogues (HIPPARCOS, FK5, FK6, etc.) this catalogue can be used as anindependent source of the proper motions of the fundamental stars.Catalogue (Table 3) is only available at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (220.127.116.11) or viahttp://cdsweb.u-strastg.fr/cgi-bin/qcat?J/A+A/365/222
|A near IR adaptive optics search for faint companions to early-type multiple stars|
We report on a high dynamical range (>10(m) ) and high angularresolution (down to 0.2arcsec ) search for low-mass components ofearly-type primaries in 7 intermediate-age (5 Myr) multiple systems withthe ESO 3.6 m telescope and the adaptive optics system ADONIS. Theimages were obtained in the J and SK bands with and without acoronographic mask of 2arcsec diameter. The census is nearly complete inthe angular separation range 1arcsec - 6arcsec , corresponding to linearseparations of 200-1200 AU, which have remained unstudied so far due tothe intrinsic brightness of the massive primaries. The best detectionlimits are around K=15(m) at 1arcsec and K=19(m) at 5arcsec separationfrom the primary. In 13 fields of 12.5arcsec x 12.5arcsec 6 new faintstars were detected. Their magnitudes and colours indicate that 2 ofthem can be physical low-mass components. The bright (K=11.2, J-K=1.2)companion to HD 108250 C at 2.17arcsec has an IR excess and deservesfurther study. Several fields were explored without a mask; somewhatsurprisingly, no new components at sub-arcsecond separations down to0.2arcsec were detected. The first order stability analysis indicatesthat the studied multiple systems are hierarchical at spatial scales of40-1000 AU. The data are briefly discussed in the light of the formationand evolution of multiple systems with massive primaries. Based onobservations collected at the ESO La Silla Observatory (program58.D-0455).
|44 Leonis Minoris and the "Pleiades Supercluster"|
|An All-Sky Catalog of Faint Extreme Ultraviolet Sources|
We present a list of 534 objects detected jointly in the ExtremeUltraviolet Explorer (EUVE) 100 Angstroms all-sky survey and in theROSAT X-Ray Telescope 0.25 keV band. The joint selection criterionpermits use of a low count rate threshold in each survey. This lowthreshold is roughly 60% of the threshold used in the previous EUVEall-sky surveys, and 166 of the objects listed here are new EUV sources,appearing in neither the Second EUVE Source Catalog nor the ROSAT WideField Camera Second Catalog. The spatial distribution of this all-skycatalog shows three features: an enhanced concentration of objects inUrsa Major, where the Galactic integrated H I column reaches its globalminimum; an enhanced concentration in the third quadrant of the Galaxy(lII from 180 deg to 270 deg) including the Canis Major tunnel, whereparticularly low H I columns are found to distances beyond 200 pc; and aparticularly low number of faint objects in the direction of the fourthquadrant of the Galaxy, where nearby intervening H I columns areappreciable. Of particular interest is the composition of the 166detections not previously reported in any EUV catalog. We offerpreliminary identifications for 105 of these sources. By far the mostnumerous (81) of the identifications are late-type stars (F, G, K, M),while 18 are other stellar types, only five are white dwarfs (WDs), andnone are extragalactic. The paucity of WDs and extragalactic objects maybe explained by a strong horizon effect wherein interstellar absorptionstrongly limits the effective new-source search volume and, thereby,selectively favors low-luminosity nearby sources over more luminous butdistant objects.
|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 (18.104.22.168) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
|High S/N Echelle spectroscopy in young stellar groups. II. Rotational velocities of early-type stars in SCO OB2.|
We investigate the rotational velocities of early-type stars in the ScoOB2 association. We measure v.sin(i) for 156 established and probablemembers of the association. The measurements are performed with threedifferent techniques, which are in increasing order of expectedv.sin(i): 1) converting the widths of spectral lines directly tov.sin(i), 2) comparing artificially broadened spectra of low v.sin(i)stars to the target spectrum, 3) comparing the HeI λ4026 lineprofile to theoretical models. The sample is extended with literaturedata for 47 established members of Sco OB2. Analysis of the v.sin(i)distributions shows that there are no significant differences betweenthe subgroups of Sco OB2. We find that members of the binary populationof Sco OB2 on the whole rotate more slowly than the single stars. Inaddition, we find that the B7-B9 single star members rotatesignificantly faster than their B0-B6 counterparts. We test varioushypotheses for the distribution of v.sin(i) in the association. Theresults show that we cannot clearly exclude any form of randomdistribution of the direction and/or magnitude of the intrinsicrotational velocity vector. We also investigate the effects of rotationon colours in the Walraven photometric system. We show that positions ofB7-B9 single dwarfs above the main sequence are a consequence ofrotation. This establishes the influence of rotation on the Walravencolours, due primarily to surface gravity effects.
|The Pulkovo Spectrophotometric Catalog of Bright Stars in the Range from 320 TO 1080 NM|
A spectrophotometric catalog is presented, combining results of numerousobservations made by Pulkovo astronomers at different observing sites.The catalog consists of three parts: the first contains the data for 602stars in the spectral range of 320--735 nm with a resolution of 5 nm,the second one contains 285 stars in the spectral range of 500--1080 nmwith a resolution of 10 nm and the third one contains 278 stars combinedfrom the preceding catalogs in the spectral range of 320--1080 nm with aresolution of 10 nm. The data are presented in absolute energy unitsW/m(2) m, with a step of 2.5 nm and with an accuracy not lower than1.5--2.0%.
|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.
|Formation Rate of Triple Stars relative to Double 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.
|A Spectrophotometric Catalogue of 60 Selected Southern Stars|
|Physical characteristics of close binary system components|
An approximate approach for evaluating the mass of invisible satellitesof close binary systems with the mass-function f(M) much less than 1 issuggested. A possibility of using it is shown for 62 close binarysystems.
|Some revisions to the Bright Star Catalogue and its supplement|
|The Pleiades supercluster in FK 5|
The age distribution of the early-type supercluster members whichdominate FK 5 is studied by means of the proper motions derived byFricke et al. (1988). The main values of the total space velocity of themembers and their dependence on radial distance from the sundemonstrates the characteristic dependence of isoperiodic galacticorbits. Models incorporating convective overshoot yield a wide range ofages, and dual epochs of star formation are identified for someindividual clusters. The results of the analysis include three widepairs of premain-sequence stars, three late-type supergiants, and oneevolved close visual binary. Recent speckle observations can be utilizedto determine the orbit of the latter binary and to determine thestructure of a potential equal-component binary comprising twomain-sequence stars. Orbital and stellar parameters are listed for theclusters which make up the Pleiades supercluster including periods,cluster parallaxes, and individual masses.
|An optical search for Beta Pictoris-like disks around nearby stars|
A coronagraphic survey of more than one hundred stars has been carriedout in a search at optical wavelengths for circumstellar materialsimilar to that found in the Beta Pictoris disk. The survey stars wereprimarily dwarfs in the spectral range A to K and most were closer than100 pc. No evidence of circumstellar material was found around any ofthe stars, suggesting that Beta Pictoris is an abnormal object,surrounded by an unusually large amount of optically scatteringmaterial.
|Physical data of the fundamental stars.|
|What ionizes the interstellar hydrogen toward PSR 0950 + 08 and PSR 0823 + 26?|
Neither H II regions around nearby B stars nor known white dwarf starscan account for the free electron column densities along twowell-defined line segments to the pulsars PSR 0950 + 08 and PSR 0823 +26. The presence of the ionized gas seems to imply either (1) very longmean free path lengths for the absorption of Lyman continuum photonswithin the ISM (thereby suggesting a very different morphology forinterstellar H I from that of the conventional view); or (2) Lymancontinuum luminosities for early B or hot white dwarf stars that aremore than an order of magnitude larger than currently accepted values;or (3) an additional and as yet unknown ionization source within theGalactic disk.
|Catalogue of i and w/w crit values for rotating early type stars|
|The volume filling factor of the infrared cirrus IS 0.2|
The filling factor of the infrared cirrus in which luminous stars areembedded is estimated. The stars are assumed to be randomly situatedwith respect to the cirrus. A direct ratio of the number of stars withassociated cirrus emission to those which in principle could be detectedindicates that the cirrus filling factor is roughly 0.2.
|Stellar integrated fluxes in the wavelength range 380 NM - 900 NM derived from Johnson 13-colour photometry|
Petford et al. (1988) have reported measured integrated fluxes for 216stars with a wide spread of spectral type and luminosity, and mentionedthat a cubic-spline integration over the relevant Johnson 13-colormagnitudes, converted to fluxes using Johnson's calibration, is inexcellent agreement with those measurements. In this paper a list of thefluxes derived in this way, corrected for a small dependence on B-V, isgiven for all the 1215 stars in Johnson's 1975 catalog with completeentries.
|Absolute fluxes for supernova 1987A. II - Days 51 to 157|
The 0.61-m Bochum telescope was used to obtain opticalspectrophotometric fluxes for SN 1987A from day 53 to day 157 after theexplosion. The evolution of the line spectrum is found to becharacterized by remarkable constancy in time, with the exception ofsome lines, including the Balmer lines. The disappearance of H-beta andH-gamma are interpreted as being related to the H-alpha Bochum event andto be due to the pervasion of radioactively heated hydrogen throughoutthe photosphere. Results are presented for absorption through equivalentwidths for H-alpha, Ca II, and Na I-D, as well as for integral linefluxes for the P Cyg emissions of Ca II and H-alpha and for theforbidden Ca II emission line at 7300 A.
|Effects of stellar rotation on the Geneva photometric system|
The effects of stellar rotation on colors and parameters of the Genevaphotometric system are considered, using homogeneous material. Attentionis focused on these parameters useful for deriving physical propertiesof B- and A-type stars. Two major photometric planes in this respect,the (X, Y) plane and the (d, Delta) plane, are not discernibly affectedby rotation. The temperature parameter, B(2) - V(1) is reddened byrotation to an extent that is in agreement with model calculations foruniformly rotating stars.
|Absolute dimensions of eclipsing binaries. XV - EM Carinae|
High-SNR coude spectrograms and uvby light curves of EM Car arepresented which have enabled the physical properties of its componentsto be determined with higher accuracy than that previously obtained forother O-type binaries. The observations reveal a slightly eccentricorbit and the presence of apsidal motion with a period of 42 years. Itis suggested that the system is still within the lower to middle part ofthe main sequence band, at an age of about 4.5-5.0 x 10 to the 6th yr.
|On the Origin of the Ptolemaic Star Catalogue - Part Two|
|Single Gaussian curve of growth abundance determinations from ultraviolet interstellar absorption-line data|
Equivalent-width data sets used in published studies of interstellarelement abundances in many sight lines are examined for evidence ofsaturation-related errors which give rise to, or enhance, the apparentcorrelations of depletion with mean hydrogen volume density, n-bar(H).It is shown that the same abundance data which exhibit a strongdependence on n-bar(H) show no tendency to correlate similarly with thestrength of optical depth of the absorption lines, in contrast to thebehavior expected if the apparent density dependence were due primarilyto effects arising from line saturation. It is demonstrated that anapparent discrepancy between S II and P II b-values is essentiallyindependent of the strength of the S II lines and n-bar(H).