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Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| Spectroscopic binaries with components of similar mass
The assertion that there is an intrinsic excess of binaries with massratios q ≃ 1 - the twin hypothesis - is investigated. A strongversion of this hypothesis (H_s), due to Lucy & Ricco (1979, AJ, 84,401) and Tokovinin (2000, A&A, 360, 997), refers to a narrow peak inthe distribution function ψ(q) for q ⪆ 0.95. A weak version(H_w), due to Halbwachs et al. (2003, A&A, 397, 159), refers to abroad peak for q ⪆ 0.8. Current data on SB2's is analysed andHs is found to be statistically significant for a samplerestricted to orbits of high precision. But claims that Hs issignificant for binaries with special characteristics are not confirmedsince the sample sizes are well below the minimum required for areliable test. With regard to H_w, additional observational evidence isnot presented, but evidence to the contrary in the form of Hogeveen's(1992, Ap&SS, 196, 299) model of biased sampling with ψ ∝q-2 is criticized. Specifically, his success in thus fittingcatalogued data depends on implausible assumptions about the researchmethodologies of binary-star spectroscopists.
| A catalogue of eclipsing variables
A new catalogue of 6330 eclipsing variable stars is presented. Thecatalogue was developed from the General Catalogue of Variable Stars(GCVS) and its textual remarks by including recently publishedinformation about classification of 843 systems and making correspondingcorrections of GCVS data. The catalogue1 represents thelargest list of eclipsing binaries classified from observations.
| Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veranderliche Sterne e.V.
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| Study of the Apsidal Motion in the Eclipsing Binary MZ Lac
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| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| The massive binary CPD - 41° 7742. II. Optical light curve and X-ray observations
In the first paper of this series, we presented a detailedhigh-resolution spectroscopic study of CPD - 41°7742, deriving for the first time an orbital solution for bothcomponents of the system. In this second paper, we focus on the analysisof the optical light curve and on recent XMM-Newton X-ray observations.In the optical, the system presents two eclipses, yielding aninclination i77°. Combining the constraints from the photometrywith the results of our previous work, we derive the absolute parametersof the system. We confirm that the two components of CPD -41° 7742 are main sequence stars (O9 V + B1-1.5 V) withmasses (M_118 Mȯ and M_210 Mȯ)and respective radii (R_17.5 Rȯ and R_25.4Rȯ) close to the typical values expected for such stars.We also report an unprecedented set of X-ray observations that almostuniformly cover the 2.44-day orbital cycle. The X-ray emission fromCPD - 41° 7742 is well described by atwo-temperature thermal plasma model with energies close to 0.6 and 1.0keV, thus slightly harder than typical early-type emission. The X-raylight curve shows clear signs of variability. The emission level ishigher when the primary is in front of the secondary. During the highemission state, the system shows a drop of its X-ray emission thatalmost exactly matches the optical eclipse. We interpret the mainfeatures of the X-ray light curve as the signature of a wind-photosphereinteraction, in which the overwhelming primary O9 star wind crashes intothe secondary surface. Alternatively the light curve could result from awind-wind interaction zone located near the secondary star surface. As asupport to our interpretation, we provide a phenomenological geometricmodel that qualitatively reproduces the observed modulations of theX-ray emission.
| New runaway OB stars with HIPPARCOS
A Monte Carlo method for detection of runaway OB stars fromobservational data is proposed. 61 runaway OB star candidates have beendetected by an analysis of Hipparcos proper motions. The peculiartangential and total transverse velocities have been determined forthese stars. A list of the detected runaway star candidates ispresented. The evidence of a discrepancy between photometric andparallactic distances of runaway OB star candidates is presented.
| Was uns (B-R)-Diagramme ueber Bedeckungsveraenderliche sagen.
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| On the Hipparcos parallaxes of O stars
We compare the absolute visual magnitude of the majority of bright Ostars in the sky as predicted from their spectral type with the absolutemagnitude calculated from their apparent magnitude and the Hipparcosparallax. We find that many stars appear to be much fainter thanexpected, up to five magnitudes. We find no evidence for a correlationbetween magnitude differences and the stellar rotational velocity assuggested for OB stars by Lamers et al. (1997, A&A, 325, L25), whosesmall sample of stars is partly included in ours. Instead, by means of asimulation we show how these differences arise naturally from the largedistances at which O stars are located, and the level of precision ofthe parallax measurements achieved by Hipparcos. Straightforwardlyderiving a distance from the Hipparcos parallax yields reliable resultsfor one or two O stars only. We discuss several types of bias reportedin the literature in connection with parallax samples (Lutz-Kelker,Malmquist) and investigate how they affect the O star sample. Inaddition, we test three absolute magnitude calibrations from theliterature (Schmidt-Kaler et al. 1982, Landolt-Börnstein; Howarth& Prinja 1989, ApJS, 69, 527; Vacca et al. 1996, ApJ, 460, 914) andfind that they are consistent with the Hipparcos measurements. AlthoughO stars conform nicely to the simulation, we notice that some B stars inthe sample of \citeauthor{La97} have a magnitude difference larger thanexpected.
| 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.
| Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veranderlichen Serne e.V.
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| Apsidal Motion in Binaries: Rotation of the Components
A sample of 51 separated binary systems with measured apsidal periodsand rotational velocities of the components is examined. The ranges ofthe angles of inclination of the equatorial planes of the components tothe orbital plane are estimated for these systems. The observed apsidalvelocities can be explained by assuming that the axes of rotation of thestars are nonorthogonal to the orbital plane in roughly 47% of thesystems (24 of the 51) and the rotation of the components is notsynchronized with the orbital motion in roughly 59% of the systems (30of 51). Nonorthogonality and nonsynchrony are defined as deviations from90° and a synchronized angular velocity, respectively, at levels of1 or more.
| The Minima of the Eclipsing Binary System Y Cyg
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| Archive of Photometric Plates Obtained at Cluj Astronomical Observatory
The archive of photometric plates obtained at the AstronomicalObservatory of Cluj in the period 1952-1974 is presented. The plateinventory is made within the framework of the Wide-Field Plate Databaseproject. The plates were taken in the regions around 110 variable stars(eclipsing variables and RR Lyrae-type stars), as well as in somecomparison stars regions.
| 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.
| Detached double-lined eclipsing binaries as critical tests of stellar evolution. Age and metallicity determinations from the HR diagram
Detached, double-lined spectroscopic binaries that are also eclipsingprovide the most accurate determinations of stellar mass, radius,temperature and distance-independent luminosity for each of theirindividual components, and hence constitute a stringent test ofsingle-star stellar evolution theory. We compile a large sample of 60non-interacting, well-detached systems mostly with typical errorssmaller than 2% for mass and radius and smaller than 5% for effectivetemperature, and compare them with the properties predicted by stellarevolutionary tracks from a minimization method. To assess the systematicerrors introduced by a given set of tracks, we compare the resultsobtained using three widely-used independent sets of tracks, computedwith different physical ingredients (the Geneva, Padova and Granadamodels). We also test the hypothesis that the components of thesesystems are coeval and have the same metallicity, and compare thederived ages and metallicities with the ones obtained by fitting asingle isochrone to the system. Overall, there is a good agreement amongthe different determinations, and we provide a comprehensive discussionon the sub-sample of systems which either present problems or haveestimated metallicities. Although within the errors the published trackscan fit most of the systems, a large degeneracy between age andmetallicity remains. The power of the test is thus limited because themetallicities of most of the systems are unknown. The full version ofTable 6 is only available in the electronic form athttp://www.edpsciences.org
| Analysis of Brightness Variations in the Massive Close Binary System UU Cassiopeia
We derive the parameters of the hot, massive close binary system UU Casfrom earlier and recent photoelectric UBVR observations: M 1 = 34.5Mȯ, M 2 = 25.7M ȯ, A = 69R ȯ, and i=68°; thecomponents' limb darkening coefficients are close to 1. Our fitting ofthe light curves provides evidence for a high degree of over-contact:the components fill their inner critical surfaces by 132% and 100%. Itis possible that the appearance of the light curve is determined notonly by the distorted shapes of the components and their eclipses but,to a considerable extent, by screening by a complex envelope and theenvelope's contribution to the system's total luminosity.
| Apsidal Motion in Detached Binary Stars: Comparison of Theory and Observations
A list of 62 detached binaries having reliable data on the rotation ofthe line of apsides is considered. Theoretical estimates of the rate ofapsidal motion are obtained. These estimates are compared withobservational data. It is shown that cases in which the theoreticalestimate exceeds the observed value are several times more frequent thancases in which the theoretical value is lower than the observed one.This discrepancy increases when systems with more reliable observationaldata are considered.
| New results on the apsidal-motion test to stellar structure and evolution including the effects of dynamic tides
We revised the current status of the apsidal-motion test to stellarstructure and evolution. The observational sample was increased by about50% in comparison to previous studies. Classical and relativisticsystems were analyzed simultaneously and only systems with accurateabsolute dimensions were considered. New interior models incorporatingrecent opacity tables, stellar rotation, mass loss, and moderate coreovershooting were used as theoretical tools to compare the predictedwith the observed shifts of the position of the periastron. The stellarmodels were computed for the precise observed masses and the adoptedchemical compositions are consistent with the corresponding tables ofopacities to avoid the inherent problems of interpolation in mass and in(X, Z). The derived chemical composition for each individual system wasused to infer the primordial helium content as well as a law ofenrichment. The values found are in good agreement with those obtainedfrom various independent sources. For the first time, the effects ofdynamic tides are taken into account systematically to determine thecontribution of the tidal distortion to the predicted apsidal-motionrate. The deviations between the apsidal-motion rates resulting from theclassical formula and those determined by taking into account theeffects of dynamic tides are presented as a function of the level ofsynchronism. For systems close to synchronisation, dynamic tides causedeviations with respect to the classical apsidal-motion formula due tothe effects of the compressibility of the stellar fluid. For systemswith higher rotational angular velocities, additional deviations due toresonances arise when the forcing frequencies of the dynamic tides comeinto the range of the free oscillation modes of the component stars. Theresulting comparison shows a good agreement between the observed andtheoretical apsidal-motion rates. No systematic effects in the sensethat models are less mass concentrated than real stars and nocorrelations with the evolutionary status of the systems were detected.
| Calculation of the masses of the binary star HD 93205 by application of the theory of apsidal motion
We present a method to calculate masses for components of both eclipsingand non-eclipsing binary systems as long as their apsidal motion ratesare available. The method is based on the fact that the equation thatgives the rate of apsidal motion is a supplementary equation that allowsthe computation of the masses of the components, if their radii and theinternal structure constants can be obtained from theoretical models.For this reason the use of this equation makes the method presented heremodel dependent . We apply this method to calculate the mass of thecomponents of the non-eclipsing massive binary system HD 93205 , whichis suspected to be a very young system. To this end, we have computed agrid of evolutionary models covering the mass range of interest, andtaking the mass of the primary (M 1 ) as the only independentvariable, we solve the equation of apsidal motion for M 1 asa function of the age of the system. The mass of the primary that wefind ranges from for zero-age main-sequence models, which sets an upperlimit for M 1 , down to for an age of 2Myr. Accordingly, theupper limit derived for the mass of the secondary is in very goodagreement with the masses derived for other O8V stars occurring ineclipsing binaries.
| 149 Bedeckungssterne der BAV-Programme. Eine Analyse der Beobachtungstatigkeit seit den Angangen.
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| Bedeckungsveraenderliche mit Apsidendrehung.
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| Das Brunner Punktesystem.
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| Optical spectroscopy of X-Mega targets - I. CPD -59° 2635: a new double-lined O-type binary in the Carina Nebula
Optical spectroscopy of CPD -59° 2635, one of the O-type stars inthe open cluster Trumpler 16 in the Carina Nebula, reveals this star tobe a double-lined binary system. We have obtained the first radialvelocity orbit for this system, consisting of a circular solution with aperiod of 2.2999d and semi-amplitudes of 208 and 273kms-1.This results in minimum masses of 15 and 11Msolar for thebinary components of CPD -59° 2635, which we classified as O8V andO9.5V, although spectral type variations of the order of 1 subclass,which we identify as the Struve-Sahade effect, seem to be present inboth components. From ROSAT HRI observations of CPD -59° 2635 wedetermine a luminosity ratio log(Lx/Lbol)~-7,which is similar to that observed for other O-type stars in the CarinaNebula region. No evidence of light variations is present in theavailable optical or X-ray data sets.
| Speckle Interferometry of New and Problem Hipparcos Binaries. II. Observations Obtained in 1998-1999 from McDonald Observatory
The Hipparcos satellite made measurements of over 9734 known doublestars, 3406 new double stars, and 11,687 unresolved but possible doublestars. The high angular resolution afforded by speckle interferometrymakes it an efficient means to confirm these systems from the ground,which were first discovered from space. Because of its coverage of adifferent region of angular separation-magnitude difference(ρ-Δm) space, speckle interferometry also holds promise toascertain the duplicity of the unresolved Hipparcos ``problem'' stars.Presented are observations of 116 new Hipparcos double stars and 469Hipparcos ``problem stars,'' as well as 238 measures of other doublestars and 246 other high-quality nondetections. Included in these areobservations of double stars listed in the Tycho-2 Catalogue andpossible grid stars for the Space Interferometry Mission.
| 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 (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
| Stars with the Largest Hipparcos Photometric Amplitudes
A list of the 2027 stars that have the largest photometric amplitudes inHipparcos Photometry shows that most variable stars are all Miras. Thepercentage of variable types change as a function of amplitude. Thiscompilation should also be of value to photometrists looking forrelatively unstudied, but large amplitude stars.
| On the origin of binaries with twin components
The existence of a statistically significant excess of dwarf binarieswith mass ratios from 0.95 to 1, as first noted by Lucy & Ricco (?),is confirmed by modern data. Excess of such binaries, called twins, isfound only for periods shorter than 40 days, and in the 2-30 days periodrange they constitute 10-20% of the total binary population. Twins musthave been formed by a special mechanism. It cannot be a mass transfer incontact pre-main-sequence binaries, fission is also unlikely. As shownby Bate (2000), accretion onto a close binary shifts mass ratio towards1, so twins may originate from binaries that became close while stillsurrounded by massive envelopes. Many twins are members ofhigher-multiplicity systems and/or clusters, which probably explains anearly formation of a close binary by stellar dynamics.
| Apsidal motion in southern eccentric eclipsing binaries: YY Sgr, V523 Sgr, V1647 Sgr, V2283 Sgr and V760 Sco
Several new times of minimum light recorded with photoelectric meanshave been gathered for the early-type eccentric eclipsing binaries YYSgr (P = 2fd 63, e = 0.16), V523 Sgr (2fd 32, 0.16), V1647 Sgr (3fd 28,0.41), V2283 Sgr (3fd 47, 0.49) and V760 Sco (1fd 73, 0.03). The O - Cdiagrams are analyzed using all reliable timings found in the literatureand improved values for the elements of the apsidal motion are computed.We find more precise periods of apsidal motion of about 290, 202, 531,528 and 38.5 years for YY Sgr, V523 Sgr V1647 Sgr, V2283 Sgr and V760Sco, respectively. The corresponding internal structure constants logk_2 are derived and compared to their theoretical values. Based onobservations collected at the South Africa Astronomical Observatory,Sutherland, South Africa
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