Contingut
Imatges
Carregar la teva Imatge
DSS Images Other Images
Articles Relacionats
Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| 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.
| Precise CCD Times of Minima of Selected Eclipsing Binaries
We present 135 precise CCD minima timings for 93 eclipsing binariesobtained at Ondrejov observatory during 2003-2004.
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| 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.
| 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
| Photoelectric Minima of Selected Eclipsing Binaries
Not Available
| Limits on Pulsations in Two Eclipsing Binaries: AY Cam and RW CrB
New CCD observations of AY Cam and RW CrB are reported and analysed withemphasis on possible pulsating components in the two Algol-typeeclipsing binaries. Besides the eclipsing changes, we could not detectany additional short period signal in the light curve, thus ruling outthe presence of delta Scuti-like pulsations in both stars.
| Search for A-F Spectral type pulsating components in Algol-type eclipsing binary systems
We present the results of a systematic search for pulsating componentsin Algol-type eclipsing binary systems. A total number of 14 eclipsingbinaries with A-F spectral type primary components were observed for 22nights. We confirmed small-amplitude oscillating features of a recentlydetected pulsator TW Dra, which has a pulsating period of 0.053 day anda semi-amplitude of about 5 mmag in B-passband. We discovered newpulsating components in two eclipsing binaries of RX Hya and AB Per. Theprimary component of RX Hya is pulsating with a dominant period of 0.052day and a semi-amplitude of about 7 mmag. AB Per has also a pulsatingcomponent with a period of 0.196 day and a semi-amplitude of about 10mmag in B-passband. We suggest that these two new pulsators are membersof the newly introduced group of mass-accreting pulsating stars insemi-detached Algol-type eclipsing binary systems.Table 4 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/405/231
| Times of Minima of Eclipsing Binaries
Not Available
| Optical positions of 55 radio stars from astrolabe observations from the Yunnan Observatory
The observations by the photoelectric astrolabe at Yunnan Observatoryrelative to the Hipparcos Catalogue and the optical positions of 55radio stars were obtained from observations between 1991 and 2000. Theyall resulted from processing the photon counts obtained by means of theastrolabe after the automation of the instrument. There are 46 stars incommon with the Hipparcos Catalogue. Tables \ref{t1} and \ref{t2} arealso available in electronic form at the CDS via anonymous ftpcdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/383/1062.
| 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.
| Times of Minima of Eclipsing Binaries
Not Available
| Possible Mass and Angular Momentum Loss in Algol-Type Binaries. III. TU Cancri, FZ Delphini, AY Geminorum, VZ Leonis, FH Orionis, IU Persei, XZ Persei, and BE Vulpeculae
Orbital period variations of eight Algol-type binaries, TU Cnc, FZ Del,AY Gem, VZ Leo, FH Ori, IU Per, XZ Per, and BE Vul, are studied based onthe analysis of the O-C observations. It is discovered that the periodsof three systems, TU Cnc, FH Ori, and IU Per, show secular decrease. ForAY Gem and XZ Per, the orbital periods can be described by a suddendecrease or by two sudden changes superposed on a secular decrease. Weakevidence also shows that the orbital periods of the other three systems,FZ Del, VZ Leo, and BE Vul, are decreasing. As in other systems proposedby Qian, the decrease in the orbital periods of these systems, combinedwith their semidetached configurations, suggests that they may beundergoing secular mass and angular momentum loss due to magneticbraking. The irregular period jumps superposed on the secular decrease(e.g., in AY Gem, FH Ori, XZ Per, and BE Vul) can be explained byvariable magnetic coupling and gravity coupling between the twocomponents. However, the present secular period decrease of thesesystems may be part of a long-period periodic change (as in TT Del),which needs further investigation.
| 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
| Observational evidence and analysis of the coupling between the dynamical and the thermodynamic processes for close binaries.
Analytical methods of the orbital period, the types of its variations,the mechanisms causing the changes in the orbital period, and problemsand progresses in the orbital period study are introduced. Theproperties of the variations in te orbital period and in the lightcurve, and the connections between the changes of the orbital period andthe light curve in different types of close binaries are also reviewed.The changes of the orbital period, the variations of the light curve andtheir connections in some sample stars are studied. The statisticalrelation of the parameters in contact binaries is also investigated.
| 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.
| Possible Mass and Angular Momentum Loss in Algol-Type Binaries. II. TT Delphini, BO Monocerotis, and Y Piscium
The period variations of three Algol-type binaries, TT Del, BO Mon, andY Psc, are studied based on the analysis of the O-C observations. Theorbital period of TT Del is discovered to be decreasing at a ratedP/dt=-2.20×10-6 days yr-1, while theorbital periods of BO Mon and Y Psc vary in some complex ways. For BOMon, three abrupt changes in its orbital period are found while itundergoes secular decrease at a rate dP/dt=-2.36×10-6days yr-1. For the remaining one, Y Psc, two jumps in theorbital period are found to superpose on a rapid period decrease(dP/dt=-4.90×10-6 days yr-1). As in the caseof TU Her (Paper I), the rapid decrease in the orbital periods of thesesystems, combined with their semidetached configurations, suggests thatthey may be undergoing rapid mass and angular momentum loss (AML) due tomagnetic braking. With the present decrease rate, after(7-9)×105 yr they will evolve into contact binaries.The abrupt changes that are superposed on the rapid period decrease maybe caused by the interplay between the variable AML and variablemagnetic coupling.
| Orbital Period Changes and Possible Mass and Angular Momentum Loss in Two Algol-Type Binaries: RW Coronae Borealis and TU Herculis
The orbital period of two Algol-type binaries, RW CrB and TU Her, arestudied. It is discovered that the orbital period of RW CrB shows asecular decrease at the rate of dP/dt=-4.29x10-8 daysyr-1, while the orbital period of TU Her varies in somecomplex way. Two jumps in the orbital period are found while itundergoes secular decrease at a rate of dP/dt=-2.92x10-6 daysyr-1. The rates of decrease of the orbital periods dP/dt inother Algol-type binaries are revised and the statistical relationbetween the orbital period P and its rate of change dP/dt is alsodiscussed. The properties of the changes in the orbital period of thesesystems, combined with their semidetached configurations, demonstratethat they may be undergoing secular mass and angular momentum loss (AML)during their evolution. The irregular abrupt changes that are superposedon the secular decrease of the orbital period may be caused by someinstabilities during the mass transfer and AML.
| Accurate Positions for Radio Stars as Determined from CCD Observations in the Extragalactic Reference Frame.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....114.1679S&db_key=AST
| Photoelectric Minima and Maxima of Selected Eclipsing and Pulsating Variables
Not Available
| 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_.
| Optical positions of radio stars. I.
The optical positions of 31 radio stars obtained from the observationswith the photoelectric astrolabe at Yunnan Observatory are presented inthis paper. These are all the stars in the astrometric catalogue ofradio stars observable by our astrolabe.
| Near-Contact Binary Systems in the ROSAT All-Sky Survey
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJ...461..951S&db_key=AST
| 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.
| Near-contact binaries
Not Available
| The active dynamo stars: RS CVn, BY Dra, FK Com, Algol, W UMa, and T Tau
Not Available
| Gravitational radiation and spiralling time of close binary systems. IV
Binary systems with their primary and secondary component masses lessthan 2 solar masses have been investigated to evaluate the rate ofemission of gravitational energy (PB) and spiralling time (tau exp 0)for them. In all, 22 binary systems have been considered. It is foundthat in spite of the same mass range, these systems form two distinctgroups. New relations have been given between PB and tau exp 0 for eachgroup. For a few eccentric orbit systems the rate of decay of orbitalperiods due to the loss of energy from the system via giavitationalradiation emission has also been given and compared with a short-periodbinary pulsar.
| Optical positions of 221 radio stars obtained with the Bordeaux automatic meridian circle
From 1984 to 1990 the Bordeaux automatic meridian circle was used todetermine accurate J2000 positions of 221 radio stars. The observationswere strictly differential, a convenient number of FK5 stars being usedeach night to calculate the instrumental parameters. The mean positionswere corrected for chromatic refraction and also for photocenter effectin the case of duplicity. The asymptotic accuracy is expected to beabout 0.05 arcsec for the Northern stars with a number of observationsgreater than 25. Mean position of 3C273B is also given from 35measurements obtained in the same conditions.
| An astrometric catalogue of radio stars
The first part is presented of a radio star catalog encompassing 186objects whose selection was guided by the priority criteria of theHipparchos Input Catalogue Consortium. Since these criteria are wellsuited to the need for linkage of ground-based optical systems to radioreference frames, this first selection is also considered a suitablebase for the catalog. Seventeen categories of stellar parameters arefurnished for each of the stars, including optical and radio positions,optical and radio parallax, radial velocity, type of variability, andoptical structure.
|
Enviar un nou article
Enllaços Relacionats
- - No s'ha trobat enllaços -
Enviar un nou enllaç
Membre dels grups següents:
|
Dades d'Observació i Astrometria
Catàlegs i designacions:
|
