תוכן
תמונות
הוסף תמונה שלך
DSS Images Other Images
מאמרים קשורים
Microlensing of close binary stars
The gravity due to a multiple-mass system has a remarkable gravitationaleffect: the extreme magnification of background light sources alongextended so-called caustic lines. This property has been the channel forsome remarkable astrophysical discoveries over the past decade,including the detection and characterization of extrasolar planets, theroutine analysis of limb darkening, and, in one case, limits set on theapparent shape of a star several kiloparsec distant. In this paper, weinvestigate the properties of the microlensing of close binary starsystems. We show that in some cases it is possible to detect flux fromthe Roche lobes of close binary stars. Such observations could constrainmodels of close binary stellar systems.
| Rotational Velocities of the Components of 23 Binaries
By using high dispersion spectra obtained by the 1.8 m telescope ofBohyunsan Optical Astronomy Observatory (South Korea), multilineleast-square deconvolution of line profiles, and Fourier analysistechniques, we obtained the rotational velocities of the components of23 binary systems. The rotational velocities for nine primary, eightsecondary, and one tertiary components of these systems were determinedfor the first time. The rotational velocities for primary components ofseven systems appeared to be significantly different than thecorresponding synchronous values (more than twice as fast for fivesystems, and less than half as fast for two systems). Our velocities forAU Mon, RY Gem, and RZ Eri are significantly lower than the previouslypublished values obtained by using one or very few lines. We show thatthese discrepancies can be explained by strong blending of the lines inthe spectra of the primaries with strong lines of the secondaries, byinfluence of gaseous streams, and maybe by nonsolar chemicalcompositions.
| Period analysis of three close binary systems: TW And, TT Her and W UMi
Orbital period changes of three close binaries, TW And, TT Her and WUMi, were studied using the Kraków data base of minima ofeclipsing binaries, and new photoelectric observations obtained by theauthors. The interval of the observations spans roughly a century. Themajor orbital period change in TW And is explained by the presence of athird body with P3 = 49.6 yr and a continuous secular periodincrease. A third body, with P3 = 41.0 yr, was also found inthe system TT Her. The (O-C) diagram of W UMi can be interpreted aseither an abrupt orbital period decrease which occurred around the endof 1973 or as a secular orbital period decrease combined with cyclicchange. In this case, the orbital period of the third body is 62.2 yrand the sum of squares of residuals is lower than for a broken-line fit,therefore cyclic variations should be preferred. In all three systems,the third body is a low-mass companion.
| Programmsterne: Beobachtungen erwuenscht.
Not Available
| Programmsterne: Beobachtungen erwuenscht.
Not Available
| 35 Visual Minimum Times of 34 Eclipsing Binaries.
Not Available
| B.R.N.O. Contributions #34
Not Available
| Visual Minima Timings of Eclipsing Binaries Observed in the Years 1992 - 1996
The paper contains a list of 283 new times of minima and 77 revisedtimes of minima for 63 eclipsing binaries derived by the author fromhis visual observations.
| The Case for Third Bodies as the Cause of Period Changes in Selected Algol Systems
Many eclipsing binary star systems show long-term variations in theirorbital periods, evident in their O-C (observed minus calculated period)diagrams. With data from the Robotic Optical Transient Search Experiment(ROTSE-I) compiled in the SkyDOT database, New Mexico State University 1m data, and recent American Association of Variable Star Observers(AAVSO) data, we revisit Borkovits and Hegedüs's best-casecandidates for third-body effects in eclipsing binaries: AB And, TV Cas,XX Cep, and AK Her. We also examine the possibility of a third bodyorbiting Y Cam. Our new data support their suggestion that a third bodyis present in all systems except AK Her, as is revealed by thesinusoidal variations of the O-C residuals. Our new data suggest that athird body alone cannot explain the variations seen in the O-C residualsof AK Her. We also provide a table of 143 eclipsing binary systems thathave historical AAVSO O-C data with new values computed from the SkyDOTdatabase.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Extrema timings of some short-period variable stars
A list of recently observed minima and maxima.
| A catalogue of close binaries located in the δ Scuti region of the Cepheid instability strip
A catalogue of close eclipsing binary systems (detached andsemidetached) with at least one of the components located in the δScuti region of the Cepheid instability strip is presented. Thepositions of the stars in the instability strip are determined by theiraccurate temperatures and luminosities. Observationally detectedbinaries (20 semidetached, four detached and one unclassified) withoscillating components were included in the catalogue as a separatetable. The primaries of the oscillating Algols tend to be located nearthe blue edge of the instability strip. Using reliable luminosities andtemperatures determined by recent photometric and spectroscopic studies,we have found that at least one or two components of 71 detached and 90semidetached systems are located in the δ Scuti region of theCepheid instability strip. In addition, 36 detached or semidetachedsystems discovered by the Hipparcos satellite were also given as aseparate list. One of their components is seen in the δ Scutiregion, according to their spectral type or B - V colours. They arepotential candidate binaries with the δ Scuti-type pulsatingcomponents which need further photometric and spectroscopic studies inbetter precision. This catalogue covers information and literaturereferences for 25 known and 197 candidate binaries with pulsatingcomponents.
| A Note on the Orbital Period of TW And
History of period behaviour and corrected light elements of theeclipsing binary TW And are presented in this note.
| 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.
| Gravity-darkening exponents in semi-detached binary systems from their photometric observations. II.
This second part of our study concerning gravity-darkening presents theresults for 8 semi-detached close binary systems. From the light-curveanalysis of these systems the exponent of the gravity-darkening (GDE)for the Roche lobe filling components has been empirically derived. Themethod used for the light-curve analysis is based on Roche geometry, andenables simultaneous estimation of the systems' parameters and thegravity-darkening exponents. Our analysis is restricted to theblack-body approximation which can influence in some degree theparameter estimation. The results of our analysis are: 1) For four ofthe systems, namely: TX UMa, β Per, AW Cam and TW Cas, there is avery good agreement between empirically estimated and theoreticallypredicted values for purely convective envelopes. 2) For the AI Drasystem, the estimated value of gravity-darkening exponent is greater,and for UX Her, TW And and XZ Pup lesser than corresponding theoreticalpredictions, but for all mentioned systems the obtained values of thegravity-darkening exponent are quite close to the theoretically expectedvalues. 3) Our analysis has proved generally that with the correction ofthe previously estimated mass ratios of the components within some ofthe analysed systems, the theoretical predictions of thegravity-darkening exponents for stars with convective envelopes arehighly reliable. The anomalous values of the GDE found in some earlierstudies of these systems can be considered as the consequence of theinappropriate method used to estimate the GDE. 4) The empiricalestimations of GDE given in Paper I and in the present study indicatethat in the light-curve analysis one can apply the recent theoreticalpredictions of GDE with high confidence for stars with both convectiveand radiative envelopes.
| Beobachtungssergebnisse Bundesdeutsche Arbeitsgemeinschaft fuer Veraenderliche Sterne e.V.
Not Available
| SB9: The ninth catalogue of spectroscopic binary orbits
The Ninth Catalogue of Spectroscopic Binary Orbits(http://sb9.astro.ulb.ac.be) continues the series of compilations ofspectroscopic orbits carried out over the past 35 years by Batten andcollaborators. As of 2004 May 1st, the new Catalogue holds orbits for2386 systems. Some essential differences between this catalogue and itspredecessors are outlined and three straightforward applications arepresented: (1) completeness assessment: period distribution of SB1s andSB2s; (2) shortest periods across the H-R diagram; (3)period-eccentricity relation.
| Up-to-Date Linear Elements of Eclipsing Binaries
About 1800 O-C diagrams of eclipsing binaries were analyzed and up-todate linear elements were computed. The regularly updated ephemerides(as a continuation of SAC) are available only in electronic form at theInternet address: http://www.as.ap.krakow.pl/ephem/.
| 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
| Orbital Period Studies of Three Algols: TW And, RW Leo, and AY Vul
The changes in the orbital periods of three EA-type eclipsing binaries,TW And, RW Leo, and AY Vul, are discussed based on an analysis of theirO - C curves. For RW Leo, its orbital period was revised and, assuming acyclic oscillation in the orbital period, a period of 38.4yr wasdetermined. For the other two systems, TW And and AY Vul, their O - Cdiagrams show complex variations. Under the assumption of periodicoscillation, cyclic changes with periods of 56.4 and 78.6yr werediscovered to superimpose on upward parabolic changes, indicating asecular period increase. The secular period increases for the two binarysystems indicate that they are on an active phase of mass transfer.Assuming the oscillations in the periods to be caused by light-timeeffects due to the presence of ``third bodies'' rotating around thesebinary stars, the orbital parameters of the third bodies weredetermined. For RW Leo, it is possible to det ect an additional thirdbody photometrically and spectroscopically. However, for the other twosystems, TW And and AY Vul, it is less likely to see additional bodies,unless the orbital inclination is very small (i.e., i' < 30°).New photometric and spectroscopic observations and a careful analysis ofthose data are needed to check the presence of third bodies.
| Zur qualitat der visuellen Beobachtung kurzperiodisch Veranderlicher.
Not Available
| Vitesses radiales photoélectriques de binaires àéclipses. VI. Orbites spectroscopiques et éléments physiques de 12 étoiles doubles Photoelectric radial velocities of eclipsing binaries VI. Orbital and physical elements of 12 double stars
Spectroscopic orbits of the 12 eclipsing binary systems, TW And, CD And,RS Ari, RU Cnc, TW Cnc, UU Cnc, V788 Cyg, AW Her, MM Her, RV Lib, EW Oriand ZZ UMa are obtained from Coravel and Elodie radial velocitymeasurements. We obtain a first orbit for CD And, RS Ari, TW Cnc, andV788 Cyg. For the systems TW And, RU Cnc, UU Cnc, AW Her, MM Her, RVLib, EW Ori and ZZ UMa, the new spectroscopic orbits are either betteror of quality comparable to that previously published. The physicalproperties of these systems were estimated with the photometricparameters from available data except CD And, TW Cnc, UU Cnc, V788 Cygand RV Lib for which we found a model compatible with the observations.The systems RU Cnc, AW Her, MM Her and RV Lib belong to RS CVn group. Ingeneral these systems were difficult to observe with Coravel, on the onehand because the stars are relatively weak and on the other hand becauseof nature of the components giving peaks of correlation with weakcontrast. La plupart des observations ont étéeffectuées àl'Observatoire de Haute-Provence (CNRS).Based, in part, on observations collected at the European SouthernObservatory, la Silla, Chile. La Table 1 est disponible seulement sousforme électronique au CDS via ftp à cdsarc.u-strasbg.fr(130.79.128.5) ou viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/387/850
| 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.
| 149 Bedeckungssterne der BAV-Programme. Eine Analyse der Beobachtungstatigkeit seit den Angangen.
Not Available
| Das Brunner Punktesystem.
Not Available
| Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veraenderliche Sterne e.V.
Not Available
| 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
| Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veraenderliche Sterne e.V.
Not Available
| 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.
| Magnetic activity and evolution of Algol-type stars - II
We examine the possibility of probing dynamo action in mass-losingstars, components of Algol-type binaries. Our analysis is based on thecalculation of non-conservative evolution of these systems. We model thesystems USge and betaPer where the more massive companion fills itsRoche lobe at the main sequence (case AB) and where it has a smallhelium core (early case B) respectively. We show that to maintainevolution of these systems at the late stages which are presumablydriven by stellar `magnetic braking', an efficient mechanism forproducing large-scale surface magnetic fields in the donor star isneeded. We discuss the relevance of dynamo operation in the donor starto the accelerated mass transfer during the late stages of evolution ofAlgol-type binaries. We suggest that the observed X-ray activity inAlgol-type systems may be a good indicator of their evolutionary statusand internal structure of the mass-losing stellar components.
|
הכנס מאמר חדש
לינקים קשורים
הכנס לינק חדש
משמש של הקבוצה הבאה
|
תצפית ומידע אסטרומטרי
קטלוגים וכינוים:
|
