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The connection between the pulsational and orbital periods for eclipsing binary systems
Considering a sample of 20 eclipsing binary systems with δ Scutitype primaries, we discovered that there is a possible relation amongthe pulsation periods of the primaries and the orbital periods of thesystems. According to this empirical relation, the longer the orbitalperiod of a binary, the longer the pulsation period of its pulsatingprimary. Among the sample, the masses of the secondaries and theseparations between the components are known for eight systems for whicha logPpuls versus logF (the gravitational pull exerted pergram of the matter on the surface of the primaries by the secondaries)diagram also verifies such an interrelation between the periods. So, asthe gravitational force applied by the secondary component onto thepulsating primary increases, its pulsation period decreases. Thedetailed physics underlying this empirical relation between the periodsneeds further confirmation, especially theoretically. However, one mustalso consider the fact that the present sample does not contain asufficiently large sample of longer period (P > 5 d) binaries.
| Automatic classification of eclipsing binaries light curves using neural networks
In this work we present a system for the automatic classification of thelight curves of eclipsing binaries. This system is based on aclassification scheme that aims to separate eclipsing binary systemsaccording to their geometrical configuration in a modified version ofthe traditional classification scheme. The classification is performedby a Bayesian ensemble of neural networks trained with Hipparcos data ofseven different categories including eccentric binary systems and twotypes of pulsating light curve morphologies.
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| Statistical Constraints for Astrometric Binaries with Nonlinear Motion
Useful constraints on the orbits and mass ratios of astrometric binariesin the Hipparcos catalog are derived from the measured proper motiondifferences of Hipparcos and Tycho-2 (Δμ), accelerations ofproper motions (μ˙), and second derivatives of proper motions(μ̈). It is shown how, in some cases, statistical bounds can beestimated for the masses of the secondary components. Two catalogs ofastrometric binaries are generated, one of binaries with significantproper motion differences and the other of binaries with significantaccelerations of their proper motions. Mathematical relations betweenthe astrometric observables Δμ, μ˙, and μ̈ andthe orbital elements are derived in the appendices. We find a remarkabledifference between the distribution of spectral types of stars withlarge accelerations but small proper motion differences and that ofstars with large proper motion differences but insignificantaccelerations. The spectral type distribution for the former sample ofbinaries is the same as the general distribution of all stars in theHipparcos catalog, whereas the latter sample is clearly dominated bysolar-type stars, with an obvious dearth of blue stars. We point outthat the latter set includes mostly binaries with long periods (longerthan about 6 yr).
| CCD Times of Minima of Selected Eclipsing Binaries
682 CCD minima observations of 259 eclipsing binaries made mainly byauthor are presented. The observed stars were chosen mainly fromcatalogue BRKA of observing programme of BRNO-Variable Star Section ofCAS.
| HD 153720 - A SB2 system with twin metallic-line components
We report the results of abundance determinations for the components ofthe SB2 star HD 153720 from high resolution (R=60 000) echelle highsignal-to-noise spectra of the wavelength region 3595-10 260 Åtaken with the 2.7 m telescope of the McDonald Observatory We found thevalues of the atmospheric parameters of the primary to be effectivetemperature Teff = 7425 K and surface gravity log g,= 4.0cgs, and of the secondary to be Teff = 7125 K and log g,= 3.9cgs. The microturbulent velocity is vmicro= 2.7 kms-1 for both components, and the projected rotationalvelocity is v sin i ,= 15 km s-1 also for both components.The abundances of about 20 elements were determined with the method ofspectrum synthesis. The components of HD 153720 are metallic-linestars. Possible inconsistencies between old and new measurements ofradial velocities may be explained by the existence of third body inthis system. A review of recent high resolution spectral observations ofeight A4-F1 binaries shows that only one of these systems can beclassified as normal.Based on observations obtained at the 2.7-m telescope of the McDonaldObservatory.The data are only available in electronic form athttp://www.edpsciences.org
| Frequency spectrum of the rapidly-oscillating mass-accreting component of the Algol-type system AS Eri
The first multisite photometric campaign devoted to the rapidlyoscillating mass-accreting (primary) component of the Algol-typeeclipsing binary system AS Eri has confirmed the presence of rapidpulsations with frequency 59.03116 d-1, and revealed thesecond and third oscillation modes with frequencies 62.5631d-1 and 61.6743 d-1, respectively. These modes arerelated to the 5-6 overtone oscillations and are among the shortestperiods excited in non-magnetic MS A-F stars. The nearly equator-onvisibility of eclipsing binaries help to narrow the range of possiblemode identifications for the detectable modes as radial or(l,m)=(1,±1), (l,m)=(2,±2) and (l,m)=(2,±0). Wechecked the high-order pulsation-to-orbital synchronization (POS) usingthe trial mode identification and the Doppler effect correction forfrequencies of non-radial pulsation. We found that (l,m,n)=(1,1,5) or(2,2,5) and (l,m,n)=(2,-2,6) identifications for f1 andf2 modes respectively satisfied the high-order POS. Thesemode identifications are in agreement with the range of modes visible indisk integrated light of an equator-on visible pulsating component.The wavelength distribution of pulsation amplitudes in AS Eri is largestin the Strömgren u filter and decreases toward longer wavelengths.We place AS Eri and other known mass-accreting pulsating components ofAlgols on HR-diagram. They are located inside the instability strip onthe Main Sequence. We also discuss the peculiar evolutionary status ofprimary components in Algols and stress that they are not normal δScuti stars, but form a separate group of pulsators. Finally, we discussproximity and eclipse effects, and have simulated the effect of primaryminimum data gaps that may produce the 1/Porb alias sidelobesin DFT analysis of eclipsing binary data. Aliases from gaps in primaryminimum observations seem to be the principal limitation on spectralwindow functions in asteroseismic studies of eclipsing binaries.
| The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of 14 000 F and G dwarfs
We present and discuss new determinations of metallicity, rotation, age,kinematics, and Galactic orbits for a complete, magnitude-limited, andkinematically unbiased sample of 16 682 nearby F and G dwarf stars. Our63 000 new, accurate radial-velocity observations for nearly 13 500stars allow identification of most of the binary stars in the sampleand, together with published uvbyβ photometry, Hipparcosparallaxes, Tycho-2 proper motions, and a few earlier radial velocities,complete the kinematic information for 14 139 stars. These high-qualityvelocity data are supplemented by effective temperatures andmetallicities newly derived from recent and/or revised calibrations. Theremaining stars either lack Hipparcos data or have fast rotation. Amajor effort has been devoted to the determination of new isochrone agesfor all stars for which this is possible. Particular attention has beengiven to a realistic treatment of statistical biases and errorestimates, as standard techniques tend to underestimate these effectsand introduce spurious features in the age distributions. Our ages agreewell with those by Edvardsson et al. (\cite{edv93}), despite severalastrophysical and computational improvements since then. We demonstrate,however, how strong observational and theoretical biases cause thedistribution of the observed ages to be very different from that of thetrue age distribution of the sample. Among the many basic relations ofthe Galactic disk that can be reinvestigated from the data presentedhere, we revisit the metallicity distribution of the G dwarfs and theage-metallicity, age-velocity, and metallicity-velocity relations of theSolar neighbourhood. Our first results confirm the lack of metal-poor Gdwarfs relative to closed-box model predictions (the ``G dwarfproblem''), the existence of radial metallicity gradients in the disk,the small change in mean metallicity of the thin disk since itsformation and the substantial scatter in metallicity at all ages, andthe continuing kinematic heating of the thin disk with an efficiencyconsistent with that expected for a combination of spiral arms and giantmolecular clouds. Distinct features in the distribution of the Vcomponent of the space motion are extended in age and metallicity,corresponding to the effects of stochastic spiral waves rather thanclassical moving groups, and may complicate the identification ofthick-disk stars from kinematic criteria. More advanced analyses of thisrich material will require careful simulations of the selection criteriafor the sample and the distribution of observational errors.Based on observations made with the Danish 1.5-m telescope at ESO, LaSilla, Chile, and with the Swiss 1-m telescope at Observatoire deHaute-Provence, France.Complete Tables 1 and 2 are only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/418/989
| Asiago eclipsing binaries program. I. V432 Aurigae
The orbit and physical parameters of the previously unsolved eclipsingbinary V432 Aur, discovered by Hipparcos, have been derived with errorsbetter than 1% from extensive Echelle spectroscopy and B, V photometry.Synthetic spectral analysis of both components has been performed,yielding Teff and log g in close agreement with the orbitalsolution, a metallicity [Z/Zȯ] = -0.6 and rotationalsynchronization for both components. Direct comparison on thetheoretical L, Teff plane with the Padova evolutionary tracksand isochrones for the masses of the two components (1.22 and 1.08Mȯ) provides a perfect match and a 3.75 Gyr age. Themore massive and cooler component is approaching the base of the giantbranch and displays a probable pulsation activity with an amplitude ofΔ V = 0.075 mag and Δrad.vel. = 1.5 km s-1. Witha Teff = 6080 K it falls to the red of the nearby instabilitystrip populated by δ Sct and γ Dor types of pulsatingvariables. Orbital modeling reveals a large and bright surface spot onit. The pulsations activity and the large spot(s) suggest the presenceof macro-turbulent motions in its atmosphere. They reflect in a linebroadening that at cursory inspection could be taken as indication of arotation faster than synchronization, something obviously odd for anold, expanding star.
| Catalogue of Algol type binary stars
A catalogue of (411) Algol-type (semi-detached) binary stars ispresented in the form of five separate tables of information. Thecatalogue has developed from an earlier version by including more recentinformation and an improved layout. A sixth table lists (1872) candidateAlgols, about which fewer details are known at present. Some issuesrelating to the classification and interpretation of Algol-like binariesare also discussed.Catalogue is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/417/263
| Improved Astrometry and Photometry for the Luyten Catalog. II. Faint Stars and the Revised Catalog
We complete construction of a catalog containing improved astrometry andnew optical/infrared photometry for the vast majority of NLTT starslying in the overlap of regions covered by POSS I and by the secondincremental Two Micron All Sky Survey (2MASS) release, approximately 44%of the sky. The epoch 2000 positions are typically accurate to 130 mas,the proper motions to 5.5 mas yr-1, and the V-J colors to0.25 mag. Relative proper motions of binary components are measured to 3mas yr-1. The false-identification rate is ~1% for11<~V<~18 and substantially less at brighter magnitudes. Theseimprovements permit the construction of a reduced proper-motion diagramthat, for the first time, allows one to classify NLTT stars intomain-sequence (MS) stars, subdwarfs (SDs), and white dwarfs (WDs). We inturn use this diagram to analyze the properties of both our catalog andthe NLTT catalog on which it is based. In sharp contrast to popularbelief, we find that NLTT incompleteness in the plane is almostcompletely concentrated in MS stars, and that SDs and WDs are detectedalmost uniformly over the sky δ>-33deg. Our catalogwill therefore provide a powerful tool to probe these populationsstatistically, as well as to reliably identify individual SDs and WDs.
| VLA Radio Positions of Stars: 1978-1995
VLA astrometric positions of the radio emission from 52 stars arereported, from observations obtained between 1978 and 1995. Thepositions of these stars have been obtained and reduced in a uniformmanner. Based on our measurements, the offset of the optical (Hipparcos)frame from the radio reference frame is in agreement with the Hipparcosextragalactic link results, within their mean errors. Comparison of theVLA measurements with the Hipparcos optical positions confirms earlierestimates of the accuracy of these positions as 30 mas. Long-termmeasurements of UX Ari have improved its proper motion.
| 149 Bedeckungssterne der BAV-Programme. Eine Analyse der Beobachtungstatigkeit seit den Angangen.
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| Das Brunner Punktesystem.
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| The Evolution of Cool Algols
We apply a model of dynamo-driven mass loss, magnetic braking, and tidalfriction to the evolution of stars with cool convective envelopes; inparticular, we apply it to binary stars where the combination ofmagnetic braking and tidal friction can cause angular momentum loss fromthe orbit. For the present we consider the simplification that only onecomponent of a binary is subject to these nonconservative effects, butwe emphasize the need in some circumstances to permit such effects inboth components.The model is applied to examples of (1) the Sun, (2) BYDra binaries, (3) Am binaries, (4) RS CVn binaries, (5) Algols, and (6)post-Algols. A number of problems regarding some of these systems appearto find a natural explanation in our model. There are indications fromother systems that some coefficients in our model may vary by a factorof 2 or so from system to system; this may be a result of the chaoticnature of dynamo activity.
| Astrometric and Light-Travel Time Orbits to Detect Low-Mass Companions: A Case Study of the Eclipsing System R Canis Majoris
We discuss a method to determine orbital properties and masses oflow-mass bodies orbiting eclipsing binaries. The analysis combineslong-term eclipse timing modulations (the light-travel time [LTT]effect) with short-term, high-accuracy astrometry. As an illustration ofthe method, the results of a comprehensive study of Hipparcos astrometryand over 100 years of eclipse timings of the Algol-type eclipsing binaryR Canis Majoris are presented. A simultaneous solution of the astrometryand the LTTs yields an orbital period of P12=92.8+/-1.3 yr,an LTT semiamplitude of 2574+/-57 s, an angular semimajor axis ofa12=117+/-5 mas, and values of the orbital eccentricity andinclination of e12=0.49+/-0.05 andi12=91.7d+/-4.7d, respectively. Adopting the total mass of RCMa of M12=1.24+/-0.05 Msolar, the mass of thethird body is M3=0.34+/-0.02 Msolar, and thesemimajor axis of its orbit is a3=18.7+/-1.7 AU. From itsmass, the third body is either a dM3-4 star or, more unlikely, a whitedwarf. With the upcoming microarcsecond-level astrometric missions, thetechnique that we discuss can be successfully applied to detect andcharacterize long-period planetary-size objects and brown dwarfs aroundeclipsing binaries. Possibilities for extending the method to pulsatingvariables or stars with transiting planets are briefly addressed.
| On the Period-Luminosity-Colour-Metallicity relation and the pulsational characteristics of lambda Bootis type stars
Generally, chemical peculiarity found for stars on the upper mainsequence excludes delta Scuti type pulsation (e.g. Ap and Am stars), butfor the group of lambda Bootis stars it is just the opposite. This makesthem very interesting for asteroseismological investigations. The groupof lambda Bootis type stars comprises late B- to early F-type,Population I objects which are basically metal weak, in particular theFe group elements, but with the clear exception of C, N, O and S. Thepresent work is a continuation of the studies by Paunzen et al.(\cite{Pau97}, \cite{Pau98}), who presented first results on thepulsational characteristics of the lambda Bootis stars. Since then, wehave observed 22 additional objects; we found eight new pulsators andconfirmed another one. Furthermore, new spectroscopic data (Paunzen\cite{Pau01}) allowed us to sort out misidentified candidates and to addtrue members to the group. From 67 members of this group, only two arenot photometrically investigated yet which makes our analysis highlyrepresentative. We have compared our results on the pulsationalbehaviour of the lambda Bootis stars with those of a sample of deltaScuti type objects. We find that at least 70% of all lambda Bootis typestars inside the classical instability strip pulsate, and they do sowith high overtone modes (Q < 0.020 d). Only a few stars, if any,pulsate in the fundamental mode. Our photometric results are inexcellent agreement with the spectroscopic work on high-degree nonradialpulsations by Bohlender et al. (\cite{Boh99}). Compared to the deltaScuti stars, the cool and hot borders of the instability strip of thelambda Bootis stars are shifted by about 25 mmag, towards smaller(b-y)_0. Using published abundances and the metallicity sensitiveindices of the Geneva 7-colour and Strömgren uvbybeta systems, wehave derived [Z] values which describe the surface abundance of theheavier elements for the group members. We find that thePeriod-Luminosity-Colour relation for the group of lambda Bootis starsis within the errors identical with that of the normal delta Scutistars. No clear evidence for a statistically significant metallicityterm was detected. Based on observations from the Austrian AutomaticPhotoelectric Telescope (Fairborn Observatory), SAAO and Siding SpringObservatory.
| Photometric study of a pulsating component in the eclipsing binary Y Cam
We present CCD photometric results of the eclipsing binary Y Cam, whoseprimary component has been known to be a delta Scuti type pulsator.Observations were performed for 16 nights, including two primary minima,from November 2000 to May 2001. After correction for light variationscaused by the eclipsing phenomenon, we investigated its pulsatingfeatures in detail. We derived four pulsation frequencies of 15.0473c/d, 18.2852 c/d, 14.8203 c/d and 17.7348 c/d using all data except forthe primary eclipsing phase. The first frequency turned out to beconstant over 40 years but the other frequencies have been changed ornewly excited. It should be noted that V amplitude of the firstfrequency decreased to about a half in comparison with the previousresults.
| The evolution status of contact close binaries of early spectral types
Hertzsprung-Russel diagram is constructed for contact close binary starsof early spectral types (CE-systems) on the basis of the "Catalogue ofapproximate photometric and absolute elements of eclipsing variablestars" by Svechnikov M. A. and Kuznetsova E. F. The excess luminosity -mass, excess radius - mass, excess luminosity - mass ratio, and excessradius - mass ratio relations are obtained for these binary systems. Allcontact close binary stars of early spectral types are subdivided into 4groups: 1) massive CE-systems of the pre-main sequence; 2) massiveCE-systems of the post-main sequence; 3) low mass systems that havepassed the "role exchange" phase (q<0.5); 4) low mass systems whichhave not passed the mass exchange phase (q≥0.5). Karetnikov'sdiagram is constructed for low-mass CE-systems with q<0.5,short-period detached main-sequence systems (DMS-systems) with P<2(d)and Sp1 from F2 to A5, and semi-detached systems of the R CMa type. Theresults prove that low-mass CE-systems with q<0.5 descended fromshort-period DMS-systems having passed the stage of semi-detached R CMasystems. The spatial density of stars in every CE-group is estimatedtaking into account the effect of observational selection. The low-massstars which have experienced mass exchange are the most numerous amongCE-systems.
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| 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.
| A Complete Survey of Case A Binary Evolution with Comparison to Observed Algol-type Systems
We undertake a comparison of observed Algol-type binaries with a libraryof computed Case A binary evolution tracks. The library consists of 5500binary tracks with various values of initial primary massM10, mass ratio q0, and period P0,designed to sample the phase-space of Case A binaries in the range-0.10<=logM10<=1.7. Each binary is evolved using astandard code with the assumption that both total mass and orbitalangular momentum are conserved. This code follows the evolution of bothstars to the point where contact or reverse mass transfer occurs. Theresulting binary tracks show a rich variety of behavior that we sortinto several subclasses of case A and case B. We present the results ofthis classification, the final mass ratio, and the fraction of timespent in Roche Lobe overflow for each binary system. The conservativeassumption under which we created this library is expected to hold for abroad range of binaries, where both components have spectra in the rangeG0 to B1 and luminosity classes III to V. We gather a list of relativelywell-determined, observed hot Algol-type binaries meeting thiscriterion, as well as a list of cooler Algol-type binaries, for which weexpect significant dynamo-driven mass loss and angular momentum loss. Wefit each observed binary to our library of tracks using aχ2-minimizing procedure. We find that the hot Algolsdisplay overall acceptable χ2, confirming theconservative assumption, while the cool Algols show much less acceptableχ2, suggesting the need for more free parameters, such asmass and angular momentum loss.
| The comparative accuracy of photographic observations of radio stars observed at the Engelhardt Astronomical Observatory
At the Engelhardt Astronomical Observatory (EAO), we observedphotographic positions of 113 Galactic Radio Sources (GRS) in the systemPPM catalogue (Rizvanov & Dautov 1998). Analysis of their accuracyis made by comparison with the Hipparcos catalogue (Perryman et al.1997) and astrometric catalogue of radio stars in the radio window fromthe article of Walter et al. (1991). Table 2 is only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/375/670
| 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
| delta Scuti and related stars: Analysis of the R00 Catalogue
We present a comprehensive analysis of the properties of the pulsatingdelta Scuti and related variables based mainly on the content of therecently published catalogue by Rodríguez et al.(\cite{retal00a}, hereafter R00). In particular, the primaryobservational properties such as visual amplitude, period and visualmagnitude and the contributions from the Hipparcos, OGLE and MACHOlong-term monitoring projects are examined. The membership of thesevariables in open clusters and multiple systems is also analyzed, withspecial attention given to the delta Scuti pulsators situated ineclipsing binary systems. The location of the delta Scuti variables inthe H-R diagram is discussed on the basis of HIPPARCOS parallaxes anduvbybeta photometry. New borders of the classical instability arepresented. In particular, the properties of the delta Scuti pulsatorswith nonsolar surface abundances (SX Phe, lambda Boo, rho Pup, delta Deland classical Am stars subgroups) are examined. The Hipparcos parallaxesshow that the available photometric uvbybeta absolute magnitudecalibrations by Crawford can be applied correctly to delta Scutivariables rotating faster than v sin i ~ 100 km s{-1} withnormal spectra. It is shown that systematic deviations exist for thephotometrically determined absolute magnitudes, which correlate with vsin i and delta m1. The photometric calibrations are found tofit the lambda Boo stars, but should not be used for the group ofevolved metallic-line A stars. The related gamma Dor variables and thepre-main-sequence delta Scuti variables are also discussed. Finally, thevariables catalogued with periods longer than 0fd 25 are examined on astar-by-star basis in order to assign them to the proper delta Scuti, RRLyrae or gamma Dor class. A search for massive, long-period delta Scutistars similar to the triple-mode variable AC And is also carried out.
| Astrophysics in 1999
The year 1999 saw the arrival of a star with three planets, a universewith three parameters, and a solar corona that could be heated at leastthree ways. In addition, there were at least three papers on everyquestion that has ever been asked in astrophysics, from ``Will theUniverse expand forever?'' to ``Does mantle convection occur in one ortwo layers?'' The answers generally were, ``Yes,'' ``No,'' and ``None ofthe above,'' to each of the questions. The authors have done their bestto organize the richness around centers defined by objects, methods, andmadnesses.
| New labour on Algols: conservative or liberal?
I consider three topics related to the influence of magnetic braking,combined with tidal friction, on the orbital evolution of CVs. Firstly,I attempt to show that properties of Algols are roughly consistent withthe view that angular momentum loss (AML) takes place in systems withcool (G/K) components, but not in systems with hot (B/A) components.This is what one might expect if the AML requires an active dynamo asseen in the Sun and other cool stars. The timescale required is roughlyof the order of what might be expected by magnetic braking. Someenhanced mass loss (ML), presumably by stellar wind, also seems to benecessary in the more evolved Algol systems. Secondly, I urge thattheorists adopt a recipe for magnetic braking that is more on the linesof Stȩpień (1995) than of Skumanich (1972). Thirdly, Iargue that `interrupted magnetic braking', a mechanism often invoked toexplain the upper edge of the period gap in CVs, is not in accord withobserved properties of late M dwarfs and brown dwarfs, and that someother mechanism should be sought.
| On the Variability of F1-F9 Luminosity Class III-V Stars
Hipparcos Satellite photometry of F1-F9 luminosity class III-V starsindicates that most are not particularly variable. A few stars for whichfurther study is desirable are identified.
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