תוכן
תמונות
הוסף תמונה שלך
DSS Images Other Images
מאמרים קשורים
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.
Not Available
| 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
| Beobachtungsegebnisse Bundesdeutsche Arbeitsgemainschaft fur Veranderliche Sterne e.V.
Not Available
| The Origin of Cyclic Period Changes in Close Binaries: The Case of the Algol Binary WW Cygni
Year- to decade-long cyclic orbital period changes have been observed inseveral classes of close binary systems, including Algol, W UrsaeMajoris, and RS Canum Venaticorum systems and the cataclysmic variables.The origin of these changes is unknown, but mass loss, apsidal motion,magnetic activity, and the presence of a third body have all beenproposed. In this paper, we use new CCD observations and thecentury-long historical record of the times of primary eclipse for WWCygni to explore the cause of these period changes. WW Cyg is an Algolbinary whose orbital period undergoes a 56 yr cyclic variation with anamplitude of ~0.02 days. We consider and reject the hypotheses of masstransfer, mass loss, apsidal motion, and the gravitational influence ofan unseen companion as the cause for these changes. A model proposed byApplegate, which invokes changes in the gravitational quadrupole momentof the convective and rotating secondary star, is the most likelyexplanation of this star's orbital period changes. This finding is basedon an examination of WW Cyg's residual O-C curve and an analysis of theperiod changes seen in 66 other Algols. Variations in the gravitationalquadrupole moment are also considered to be the most likely explanationfor the cyclic period changes observed in several different types ofbinary systems.
| 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.
| Is asynchronism in semidetached binary systems real?
We analyze statistical relationships between the parameters ofAlgol-type binaries with asynchronous rotation of the primary componentsand provide observational evidence for denser, more extended gaseousenvelopes in the eclipsing systems of this group. We conclude thatasynchronism of the primary components in such systems is not real. Thelines that are used to determine the rotational velocities of thesecomponents originate mostly in the part of the atmosphere which acquiresan additional angular momentum during the interaction with the gasstream and produces a transient accretion disk near the equatorialplane.
| CCD Photometry of Five Neglected Eclipsing Binary Stars
Differential V-magnitude CCD photometric data are presented for fiveneglected eclipsing binary stars with shallow eclipses. An improvedperiod is derived for SV Equ, past O-C trends are confirmed for AN Andand DL Vir, and an unexpectedly large O-C values are found for BW DELnad CS Lac.
| On the nature of the AM phenomenon or on a stabilization and the tidal mixing in binaries. I. Orbital periods and rotation.
The paper casts a questioning eye on the unique role of the diffusiveparticle transport mechanism in explaining the Am phenomenon and arguesthat the so-called tidal effects might be of great importance incontrolling diffusion processes. A short period cutoff at =~1.2d as wellas a 180-800d gap were found in the orbital period distribution (OPD) ofAm binaries. The existence of the former can be ascribed to the state ofthe primaries with the almost-filled Roche lobes. The latter couldresult from the combined effects of the diffusion, tidal mixing andstabilization processes. Because the tidal mixing might surpassdiffusion in the binaries with the orbital periods P_orb_ less thanseveral hundred days and might thus sustain the He convection zone,which would otherwise disappear, no Am stars should lie below thisboundary. The fact that they are nevertheless seen there implies theexistence of some stabilization mechanism (as, e.g., that recentlyproposed by Tassoul & Tassoul 1992) for the binaries with orbitalperiods less than 180d. Further evidence is given to the fact that theOPD for the Am and the normal binaries with an A4-F1 primary arecomplementary to each other, from which it stems that Am stars are closeto the main sequence. There are, however, indications that they haveslightly larger radii (2.1-3 Rsun_) than expected for theirspectral type. The generally accepted rotational velocity cutoff at=~100km/s is shown to be of little value when applied on Am binaries ashere it is not a single quantity but, in fact, a function of P_orb_whose shape is strikingly similar to that of the curves of constantmetallicity as ascertained from observations. This also leads to thewell known overlap in rotational velocities of the normal and Am starsfor 402.5d.We have exploited this empirical cutoff function to calibrate thecorresponding turbulent diffusion coefficient associated with tidalmixing, having found out that the computed form of the lines of constantturbulence fits qualitatively the empirical shape of the curves ofconstant metallicity. As for larger orbital periods(20d55km/s found by Burkhart(1979) would then be nothing but a manifestation of insufficientlypopulated corresponding area of larger P_orb_.
| 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.
| DN Orionis: A Long-Period Mass-Transferring "Slightly Detached" Algol Binary
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995AJ....110.1809E&db_key=AST
| Rapid H-alpha emission variations in accretion disks in long-period ALGOLS
We demonstrate the continuous presence of large variations indouble-peaked H-alpha long period Algol-type binaries, using recentlyobtained CCD spectra. Most fluctuations occur on a time scale less thanor = an orbital period and a steady state in H-alpha emission ia neverreached. In AD Her (P = 10 d), H-alpha emission dropped in strength morethan a factor of five in one seven-day interval. Contemporay O I lambdaobservations showed no significant changes in oxygen absorption strengthor radial velocity during this time. We tentatively suggest that H-alphavariations arise from an inner-disk instability, possibly triggered bysmall modulations in the mass-transfer rate. This behavior isreminiscent of some cataclysmic variables.
| O I lamba 7774 absorption as a tracer of streams and disks in nondegenerate binary stars
We propose a new spectroscopic approach for observing circumstellarmatter in binary stars, based on the neutral oxygen lambda 7774absorption lines. We present oxygen equivalent widths and radialvelocities in 20 nondegenerate eclipsing binaries. We note limitationsand advantages of using this line to trace circumstellar matter inbinary systems, and confirm the presence of streams and rotatingaccretion disks in a number of short- long-period Algol systems. Wediscuss evidence for geometrically thick disks, and describe a smallradial infall superimposed on disk rotation in most long-period systems.We speculate that infall may be related to viscous dissipation in disks.We emphasize the great sensitivity of lambda 7774 in studying thekinematics of circumstellar matter in many nondegenerate binary stars.
| Rapid Hα Emission Variations in Accretion Disks in Long-Period ALGOLS
We have measured some 500 equivalent widths of red and violet Hαemission lobes in nine long-period Algol binaries with periods from 7 to262 days. In most systems, both lobes underwent large, nearly chaotic,variations in times less than or comparable to an orbital period. On oneoccasion in AD Herculis, emission in both lobes nearly disappeared injust over half the period. Fractional variations generally decreasedtoward longer period. No clear correlation exists between variations andorbital phase. There was a general increase in emission equivalent widthwith increasing binary period, as the volume between the mass-gainingstar and its Roche lobe increases. The Huang-Struve relation betweendisk orbital velocity and period holds to P=30 days. There is noevidence of an actual physical collapse of disk matter; rather,variations in kinetic temperature probably account for emissionvariations. Contemporary observations of the disk absorption line O Ilambda 7774 show no significant temporal variations. Hα emissionoriginates largely in the inner disk, while oxygen absorption arisesfrom the outer parts of the disk, where scale heights are large.Therefore, accretion-disk instability occurs mainly in the inner disk.This behavior mimics that seen in some cataclysmic binaries.
| New rotational velocities for eclipsing binaries, and a comparison of spectroscopic and photometric rotations
Rotational velocities are determined spectroscopically for 38 eclipsingbinaries, including many long-period, nominally semidetached, systems.We note that spectroscopic rotations may differ from rotations derivedfrom light-curve modeling using the Wilson-Devinney program. In'direct-impact' mass-transferring systems, or in most systems withperiods smaller than about 7 days, observations suggest that the tworotations are usually about the same. In cases where the stream missesthe gainer and an accretion disk forms, however, photometric rotationestimates often exceed spectroscopic determinations. The possiblephysical significance of this situation is briefly discussed. Doubt iscast on the likelihood that the rotation of the hot component of U Sgehas changed detectably in the last 30 years.
| Eclipsing binaries in multiple-star systems
Some 80 eclipsing binaries that are components of multiple-star systemsare considered. Orbits for the third components of these systems aredetermined for only a relatively small number of cases, and all of thesethat have been published to date are presented. Triple-star systems areby far the most common of these, but one system in five is a quadrupleor higher-order system. Eclipsing binaries in compact star clusters suchas SZ Camelopardalis and the two binaries in Trapezium, BM Ori, and V1016 Ori are also considered. The physical and orbital properties of themultiple star systems are discussed in detail in cases where the dataare fairly complete. In triple-star systems with eclipsing binaries theratio of P2/P1 ranges from less than 10 (for Lambda Tauri) to more than10 exp 7 in some cases. The questions of coplanarity of orbits and themembership of components in multiple-star systems are also examined.
| Statistical study of semi-detached and near-contact semi-detached binaries
A statistical study was made of 107 semidetached with combined lightcurve solutions. An empirical period-dependent mass-radius relation wasderived, thereby revealing the impossibility of having evolvedsemidetached systems with very short periods. Statistically, thenear-contact semidetached systems have the common properties of nearlyequal mass densities of the components, larger mass-ratios, shorterperiods and smaller specific angular momenta, and their A- F-typesecondaries generally have greater densities than the secondaries ofclassical Algol systems of the same spectral types. A detaileddiscussion is also made in this paper on the evolution of near-contactsemidetached binaries.
| Radial velocities in 12 Algol binaries
Radial velocities derived from photometric analysis of the Na D linesfor the cooler components of the 12 Algol systems are discussed. Thenumber of velocities per system at the D lines ranges from 6 to 63, andin each case, the velocities are well represented by circular motion.For a 5-day period, the spectra of the primaries in RY Aqr, TW Dra, TWAnd, and RS Vul appear to be completely photospheric, while the othereight systems, Rx Gem, Ry Gem, AD Her, TT Hya, Au Mon, RW Per, RY Per,and XY Pup, show double H-alpha emission and other evidence ofnonphotospheric material in the hotter spectra. For most of thesesystems of longer period, the velocities are quite well represented bypseudoelliptical motion, with minimum velocities and maximum departuresfrom circular motion near phase 0.4, measured from primary minimum.Provisional masses are given for the stars based on the availablespectroscopic and photometric evidence, much of it of low weight. Thecompanions of the primaries with A-type spectra have masses of 0.75solar mass or less, and temperatures or types in the early K range asobserved in RY Aqr. All the secondaries are larger than main-sequencestars of the corresponding types.
| A summary of the investigations of semi-detached close binaries (1986-1988)
Not Available
| Statistical Study on the Semidetached and Near Contact Semidetached Binary Systems
Not Available
| An Updated List of Eclipsing Binaries Showing Apsidal Motion
Not Available
| Semidetached systems - Evolutionary viewpoints and observational constraints
The present knowledge on the evolution of semidetached systems isreviewed. Characteristics of observed systems are discussed and generalproperties tested by the behavior of theoretical models. New models ofmass accreting companion stars are computed. The accretion phase isdivided into a fast and slow phase with an accretion rate depending onthe initial mass of the mass losing star and on the initial mass ratio,asssuming the systems are undergoing a case B of mass transfer. Theresults are compared with observed systems with masses of the gainerslocated within the theoretical range. Up to now no computations existfor the evolution of medium mass close binaries including overshootingof the convective core. However some of the influences of extendedconvective mixing on the interaction of close binaries are investigated.A larger probability for the occurrence of case A of mass exchange and alarger remnant mass at the end of the process are the most importantresults. Finally the investigation into the origin of individual systems(in mass, mass ratio and period) is discussed, showing that progressboth in observations and in theoretical models result in a more detailedand more restricted determination of the initial parameters of theindividual systems.
| Absolute parameters of stars in semidetached eclipsing binary systems
A number of questions concerning the absolute parameters of stars insemidetached binary systems are addressed. Consideration is given to:similarities between Algol-type binaries and unevolved detached binarieswith respect to the mass-luminosity law; and the single-line classicalAlgol candidates with known mass functions and photometric solutions formass ratio. It is shown that the validity of the mass luminosity-lawcannot be verified for individual Algol-type binaries though it doeshold well on average; and (2), the existence of a definite class ofsd-binaries not containing a proportion of significantly undersize typesis apparent. The conclusions are found to be in general agreement withthe observations of Hall and Neff (1979).
| Spectroscopic binaries - 14th complementary catalog
Orbital-element data for 380 spectroscopic binaries are compiled andannotated in tables. The catalog represents a continuation of the 13thcatalog (Pedoussaut and Nadal, 1977) and uses the same general format.The techniques used in making the magnitudes and spectral typeshomogeneous are indicated.
| A Catalogue of Classical Evolved Algol-Type Binary Candidate Stars
Not Available
| Main-sequence components of Algol-type binaries as blue stragglers
The hot components of Algol-type binaries which are main-sequence starsgenerally have positions in the H-R diagram which correspond to theirmasses. Consequently they look like old main-sequence stars. However,the real age of a system in which transfer and loss of matter hasoccurred may be greater than the apparent age of the most massivecomponent. Some evolved binaries have been selected which, underreasonable hypotheses, are estimated to be in this situation. Therelation to the blue-straggler problem is examined.
| Statistics of categorized eclipsing binary systems Lightcurve shapes, periods, and spectral types
The statistics of the light curve morphologies, eclipse depths, orbitalperiods, and spectral types of about 1000 eclipsing binary systems areexamined, after attempting to subdivide these binaries into variousbasic evolutionary categories. The applicability of statisticalcriteria, based on light curve morphologies and eclipse depths, for thecategorization of eclipsing binaries has been found more limited thanpreviously believed. In particular, EW-type light curves turn out to begood indicators of contact systems (though not conversely), while EA-and EB-type light curves have little physical significance. Moreover,the study reveals a strong deficit of short-period noncontact systems inthe whole spectral range, together with an underabundance of early-typecontact binaries (compared with the number of late-type contact pairs).Interestingly, the distribution of evolved Algol-type systems isshifted, on average, to periods longer than those of unevolved detachedsystems in the OB and early A spectral range (and to shorter periods inthe F spectral range).
| Mass transfer in close binary systems - Original and remnant masses
Masses of numerous Algol binaries (and a few Wolf-Rayet systems) arecompared with new theoretical predictions in which the effect ofovershooting in stellar interiors is considered. The comparison appearsto confirm that usual mass-transfer computations cannot satisfactorilyaccount for the observed masses of the post-mass exchange remnants. Itis suggested that the incongruities which hinder a quantitativeevaluation of the amount of mass loss from close binaries may be relatedto the possible occurrence of complicated interactive processes,including phases of contact configurations, which might drasticallymodify the outcome of mass-transfer processes.
| General properties of Algol binaries
Theoretical computations on close binary evolution have made it possibleto obtain a general understanding of the evolutionary scenario of Algolvariables in terms of mass exchange. The present investigation has theobjective to draw attention to some important discrepancies between theobservational data of Algol variables and the relevant theoreticalresults. A compilation of the observed properties of 101 Algol variablesis presented. This term is used to denote binaries related to theclassical Algol variables from the evolutionary point of view. Attentionis given to the statistical properties of the binaries of the selectedsample, taking into account a comparison of the binaries with similaravailable statistical analyses of a large sample of eclipsing andspectroscopic binaries. An order-of-magnitude estimate is provided ofthe amount of mass ejected into the interstellar space by Algol binariesas a result of nonconservative mass-transfer processes.
|
הכנס מאמר חדש
לינקים קשורים
הכנס לינק חדש
משמש של הקבוצה הבאה
|
תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | הרקולס |
| התרוממות ימנית: | 18h50m00.30s |
| סירוב: | +20°43'16.5" |
| גודל גלוי: | 9.725 |
| תנועה נכונה: | -1.8 |
| תנועה נכונה: | -6.9 |
| B-T magnitude: | 10.151 |
| V-T magnitude: | 9.761 |
קטלוגים וכינוים:
|
