Contents
Images
Upload your image
DSS Images Other Images
Related articles
DASCH on KU Cyg: A ~ 5 year Dust Accretion Event in ~ 1900
KU Cyg is an eclipsing binary consisting of an F-type star accretingthrough a large accretion disk from a K5III red giant. Here we presentthe discovery of a 5 year dip around 1900 found from its 100 year DASCHlight curve. It showed a ~0.5 mag slow fading from 1899 to 1903 andbrightened back around 1904 on a relatively shorter timescale. The lightcurve shape of the 1899-1904 fading-brightening event differs from thedust production and dispersion process observed in R Coronae Borealisstars, which usually has a faster fading and slower recovery, and for KUCyg is probably related to the accretion disk surrounding the F star.The slow fading in KU Cyg is probably caused by increases in dustextinction in the disk, and the subsequent quick brightening may be dueto the evaporation of dust transported inward through the disk. Theextinction excess which caused the fading may arise from increased masstransfer rate in the system or from dust clump ejections from the Kgiant.
| Bayesian inference of stellar parameters and interstellar extinction using parallaxes and multiband photometry
Astrometric surveys provide the opportunity to measure the absolutemagnitudes of large numbers of stars, but only if the individualline-of-sight extinctions are known. Unfortunately, extinction is highlydegenerate with stellar effective temperature when estimated frombroad-band optical/infrared photometry. To address this problem, Iintroduce a Bayesian method for estimating the intrinsic parameters of astar and its line-of-sight extinction. It uses both photometry andparallaxes in a self-consistent manner in order to provide anon-parametric posterior probability distribution over the parameters.The method makes explicit use of domain knowledge by employing theHertzsprung-Russell Diagram (HRD) to constrain solutions and to ensurethat they respect stellar physics. I first demonstrate this method byusing it to estimate effective temperature and extinction from BVJHKdata for a set of artificially reddened Hipparcos stars, for whichaccurate effective temperatures have been estimated from high-resolutionspectroscopy. Using just the four colours, we see the expected strongdegeneracy (positive correlation) between the temperature andextinction. Introducing the parallax, apparent magnitude and the HRDreduces this degeneracy and improves both the precision (reduces theerror bars) and the accuracy of the parameter estimates, the latter byabout 35 per cent. The resulting accuracy is about 200 K in temperatureand 0.2 mag in extinction. I then apply the method to estimate theseparameters and absolute magnitudes for some 47 000 F, G, K Hipparcosstars which have been cross-matched with Two-Micron All-Sky Survey(2MASS). The method can easily be extended to incorporate the estimationof other parameters, in particular metallicity and surface gravity,making it particularly suitable for the analysis of the 109stars from Gaia.
| The most plausible explanation of the cyclic period changes in close binaries: the case of the RS CVn-type binary WW Dra
Cyclic period changes are a fairly common phenomenon in close binarysystems and are usually explained as being caused either by the magneticactivity of one or both components or by the light travel time effect(LTTE) of a third body. We searched the orbital period changes in 182EA-type (including the 101 Algol systems used by Hall), 43 EB-type and53 EW-type binaries with known mass ratio and spectral type of thesecondary component. We reproduced and improved the diagram in Hallaccording to the new collected data. Our plots do not support theconclusion derived by Hall that cyclic period changes are restricted tobinaries having a secondary component with spectral type later than F5.The presence of period changes among systems with a secondary componentof early type indicates that magnetic activity is one, but not the only,cause of the period variation. It is discovered that cyclic periodchanges, probably resulting from the presence of a third body, are morefrequent in EW-type binaries among close systems. Therefore, the mostplausible explanation of the cyclic period changes is the LTTE throughthe presence of a third body. Using the century-long historical recordof the times of light minimum, we analysed the cyclic period change inthe Algol binary WW Dra. It is found that the orbital period of thebinary shows a ~112.2-yr cyclic variation with an amplitude of ~0.1977d.The cyclic oscillation can be attributed to the LTTE by means of a thirdbody with a mass no less than 6.43Msolar. However, nospectral lines of the third body were discovered, indicating that it maybe a candidate black hole. The third body is orbiting the binary at adistance closer than 14.4 au and may play an important role in theevolution of this system.
| A period study and light-curve synthesis for the Algol-type semidetached binary XXCephei
We obtained CCD photometric observations of the Algol-type semidetachedbinary XXCephei (XXCep) during 15 nights from 2002 September 17 to 2003February 2, and also on 2005 January 21. Except for those data taken onthe last night of the concentrated observing season, the 3881measurements were obtained over an interval of only 106 nights. Fromthese data, four new times of minimum light were calculated. The (O- C)diagram formed from all available timings, and thus the orbital periodof the system, can be partly represented as a beat effect between twocyclical variations with different periods (yr, yr) and amplitudes(K1=0.015d, K2=0.103d), respectively. Bothphysical and non-physical interpretations of these cycles wereinvestigated. The long-term sinusoidal variation is too long formagnetic cycling in solar-type single and close binary stars. Inaddition, we have studied the effect of a possible secular periodvariation. By analysing the residuals from our Wilson-Devinney (WD)binary model, we found small light variations with a period of 5.99dwith amplitudes growing toward longer wavelengths. We think that theseoscillations may be produced by instabilities at the systemicL1 point (also occupied by the point of the cool star) andthat these instabilities are, in turn, caused by non-uniform andsporadic convection. There is also a short-period oscillation of about45min in the WD light residuals that is attributed to accretion on tothe mass-gaining primary component from a feeble gas stream originatingon the cool donor star.
| A spectroscopic study of the Algol-type binaries S Equulei and KO Aquilae: absolute parameters and mass transfer
We present and analyse high-resolution optical spectra of two Algolbinaries, namely S Equ and KO Aql, obtained with the echellespectrograph at Catania Astrophysical Observatory. New accurate radialvelocities (RVs) for the hotter primary components are obtained. Thanksto the cross-correlation procedure, we were able to measure, for thefirst time to our knowledge, RVs also for the cool secondary componentsof S Equ and KO Aql. By combining the parameters obtained from thesolution of the RV curves with those obtained from the light-curveanalysis, reliable absolute parameters of the systems have been derived.The rotational velocity of the hotter components of S Equ and KO Aql hasbeen measured and it is found that the gainers of both systems rotateabout 30 per cent faster than synchronously. This is likely due to masstransfer across the Lagrangian L1 point from the cooler tothe hotter component. The lower luminosity of the mass-gainingcomponents of these systems compared to normal main-sequence stars ofthe same mass can also be an effect of the mass transfer. The Hαprofiles were analysed with the `synthesis and subtraction' techniqueand reveal clear evidence of mass transfer and accretion structures. Inboth systems, especially before the primary eclipses and afterwards, weclearly observed extra absorption lines. From the integrated absorptionand the RV variations of these features, we found that the massaccretion is very dense around the impact region of the hottercomponents. A double-peaked emission in the spectra of S Equ was seenoutside the eclipses. One of these peaks is likely originated in aregion between the centre of mass and the cooler component, which isoccupied by the flowing matter. Furthermore, the Hα differencespectra of S Equ and KO Aql also display emission features, which shouldbe arising from the magnetic activity of the cooler components.Based on observations collected at the Catania Astrophysical Observatory(Italy).E-mail: fsoydugan@comu.edu.tr
| 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 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.
| 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
| 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.
| Einige interessante Bedeckungsveraenderliche.
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.
| Light-Curve Synthesis for Close Binaries: Elliptical Disk around a White Dwarf
We present an algorithm for the synthesis of the light curve of a closebinary system consisting of a red dwarf that fills its Roche lobe and aspherical white dwarf. The spherical component is surrounded by anelliptical accretion disk with a complex shape, geometrically thin nearthe spherical star and geometrically thick at the edge of the disk. Themodel is able to describe the shape of the secondary minimum in thelight curve of the eclipsing variable KU Cyg, which has not beenpossible using other models.
| Is the eclipsing variable EE CEP a cousin of epsilon Aur?
We report the first five-colour Johnson UBVRI observations of the lasteclipse of the long-period (5.7 yr) eclipsing binary EE Cep. We proposethat the star is a member of the Cep OB1 association at a distance of2.75 kpc. Using this assumption, we find that the primary is a B5 brightgiant of radius ~ 10 R_solar and luminosity M_v ~ -3.1. The observationsshow that the obscuring body is not a star-like object. We suggest thatthe invisible companion in EE Cep is a dark, thick disc around alow-luminosity central star or binary, and that the system has a fewimportant similarities to the epsilon Aur system.
| Catalogue of H-alpha emission stars in the Northern Milky Way
The ``Catalogue of Stars in the Northern Milky Way Having H-alpha inEmission" appears in Abhandlungen aus der Hamburger Sternwarte, Band XIin the year 1997. It contains 4174 stars, range {32degr <= l() II< 214degr , -10degr < b() II < +10degr } having the Hαline in emission. HBH stars and stars of further 99 lists taken from theliterature till the end of 1994 were included in the catalogue. We givethe cross-identification of stars from all lists used. The catalogue isalso available in the Centre de Données, Strasbourg ftp130.79.128.5 or http://cdsweb.u-strasbg.fr and at the HamburgObservatory via internet.
| A Photometric and Spectrophotometric Study of MR Cygni
A self-consistent, physically accurate program suite has been used in anaccurate simulation of new spectroscopy and photometry of MR Cygni.Analysis of both the spectroscopic and photometric data used spectrumsynthesis techniques and a synthetic photometry augmentation of a lightsynthesis program package. The theoretical light curves closely fit theobservational data. The same self-consistent parameters from the lightsynthesis solution produced synthetic spectra precisely fitting theobserved spectra at all orbital phases. The IRAF-reduced spectroscopyhas produced an accurate double-lined radial velocity curve. The derivedmass ratio differs greatly from photometric mass ratios in theliterature. New UBV photometry closely replicates existing data andindicates photometric stability of the binary system. A syntheticspectrum fitted to IUE data established the primary component Teff. Thelight curve solution determined a single set of system parameters usedto calculate U, B, and V light curves. We conclude that MR Cygni is amember of the relatively rare class of hot Algol systems defined byPopper. It is likely that mass transfer still is in progress, but thereis no evidence, either from orbital period variation or from a brightspot on the mass gainer, for its existence. The lack of H alpha emissionin any of our spectra, including one at phase 0.063, suggests a smallcurrent rate of mass transfer. The fact that our computationallyself-consistent procedure has successfully represented both thephotometry and the spectroscopy for a binary system whose components areappreciably distorted demonstrates the overall power of the procedure.
| KU CYG and its Eccentric Accretion Disk
The profile of the H alpha emission line from the accretion disk,observed in March 1989, at phase phi=-0.0447, when the approaching partof the disk was partly eclipsed by the secondary, shows effects of alarge disk eccentricity and of its finite geometrical thickness. Thelatter produces obscuration of the inner surface of the disk by itsouter edge, an effect which strongly depends on inclination. Analysis ofthe observed profile allows determination of the major semi-axis of thedisk: a_d=0.48+/-0.01, its eccentricity e_d=0.31+/-0.07, and the orbitalinclination: i=86.0+/-0.1. With this inclination, the solution based onphases of contacts of the primary eclipse gives q=M_2/M_1=0.13+/-0.01which, together with K_2=90.7 km/s (Olson et al. 1995), givesM_1=3.83+/- 0.07Modot, M_2=0.50+/-0.04Modot, andA=(5.43+/-0.04) times 1012 cm. Photometric and spectroscopicdata available for KU Cyg suggest behavior similar to that observed indwarf novae of the SU UMa type (Osaki 1989): The disk becomesoccasionally very large, eccentric, and precessing. Tidal effects,removing angular momentum from its outer parts, result then in anenhanced accretion; while insufficient to produce thermal instability,it is observable as a minor brightening. In the case of KU Cyg theseprocesses have characteristic time scales of, roughly, few years.
| Catalogue of stars in the northern Milky Way having H-alpha in emission
Not Available
| W Crucis: an eclipsing binary system containing an accretion disk.
Recently published B and V light curves of W Cru have been analyzed bymeans of the light curve synthesis. A consistent model of the system canbe obtained if a thick accretion disk is introduced. The disk completelyobscures the more massive, mass accreting star, explaining the problemof its invisibility in the spectrum. In this model, the deeper minimumis the one caused by the eclipse of the mass losing star by the disk.Masses of the components were calculated to be M_1_=7.8Msun_,M_2_=1.25Msun_, the orbital separation A=299Rsun_,while the radius of the secondary R_2_=76Rsun_. The systemseems to be a product of the 'Case-C' mass transfer evolution.
| 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.
| UX Monocerotis: New Photometric and Spectroscopic Observations, Solutions, and Anomalies in an Active Mass-Transferring Binary
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995AJ....110.2385O&db_key=AST
| KU Cygni: New Spectroscopic and Photometric Solutions of a Long-Period Accretion-Disk Binary
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995AJ....110.2378O&db_key=AST
| 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
| 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.
| RS Cephei: New photometric solutions including rapid rotation, and new spectroscopic observations
Using the Wilson program, new system parameters for the long-periodmass-transferring binary RS Cephei are derived from new spectroscopicobservations and a new solution of Olson's photometric data.Color-dependent uncertaintities in the photometric mass ratio arediscussed. I through v observations made from 1980 to 1985 areessentially free of circumsteller contamination, but a simultaneousIybvu solution reveals about 0.6 mag of excess ultraviolet radiation inprimary eclipse totality, probably from uneclipsed continuous emissionfrom an accretion disk around the hotter star. The ultraviolet diskluminosity will help to constrain estimates of the physical propertiesof the disk, to be found later.
| Radio continuum emission from stars: a catalogue update.
An updated version of my catalogue of radio stars is presented. Somestatistics and availability are discussed.
| Rediscussion of photometric data and an accretion disk model for the 96-day binary UU CANCRI
Available photometric data of UU Cnc were reanalyzed in order to checkfor the presence of an accretion disk in the system. Light curvemodeling made with a code that simulates a light curve of a binarycontaining an accretion disk was performed. Results show that such amodel describes the observed B and V light curves very well. The systemwas found to consist of a more massive star completely hidden by anoptically thick accretion disk and of a 0.77Msun_ K4 IIIgiant with radius of about 37Rsun_. The system mass ratio wasderived to be about 0.56 and inclination close to 90 degrees. The diskseen edge-on contributes to the observed light curves very little. Itsmain effect in the light curve is due to its eclipse of the giant starobserved as the deeper minimum. Such a model could explain some cases ofthe β -Lyr paradox - invisibility in the spectrum of the moremassive star due to its obscuration by an optically thick accretiondisk, in systems with inclination close to 90 degrees.
| KU CYG - The Algol-type binary with an accretion disk
Four color photometric data of KU Cyg, an Algol-type eclipsing binarycontaining an accretion disk, obtained by Olson, were analyzed in orderto obtain the physical parameters of the components of the system and ofthe accretion disk. Light curve analysis was performed using a model ofa binary containing an accretion disk around the primary star. Theprimary star was found to have temperature of about 10,300 K, radius ofabout 3.2 solar radii and mass of about 2.6 solar masses. The secondarystar is less massive (0.6 solar masses) and has the radius of about 18solar radii. The radius of the disk is about 32 solar radii which isabout 90 percent of the primary star Roche lobe. The primary starparameters indicate that it is close to the main sequence.
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
| Constellation: | Schwan |
| Right ascension: | 20h12m45.10s |
| Declination: | +47°23'41.4" |
| Apparent magnitude: | 11.053 |
| Proper motion RA: | -4.7 |
| Proper motion Dec: | 2.8 |
| B-T magnitude: | 11.851 |
| V-T magnitude: | 11.119 |
Catalogs and designations:
|
