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.
|
Orbital Evolution of Algol Binaries with a Circumbinary Disk
It is generally thought that conservative mass transfer in Algolbinaries causes their orbits to be wider, so that the less massive staroverflows its Roche lobe. The observed decrease in the orbital periodsof some Algol binaries suggests orbital angular momentum loss during thebinary evolution, and the magnetic braking mechanism is often invoked toexplain the observed orbital shrinkage. Here we suggest an alternativeexplanation, in which a small fraction of the transferred mass forms acircumbinary disk, which extracts orbital angular momentum from thebinary through tidal torques. We also perform numerical calculations ofthe evolution of Algol binaries with typical initial masses and orbitalperiods. The results indicate that, for reasonable input parameters, thecircumbinary disk can significantly influence the orbital evolution, andcause the orbit to shrink on a sufficiently long timescale. Rapid masstransfer in Algol binaries with low mass ratios can also be accountedfor in this scenario.
|
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.
|
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.
|
Minima Kurt Locher 2004-2005
Minima observed 2004..2005 by Kurt Locher visually, not accepted by IBVSas part of BBSAG Bulletin.
|
164. List of Timings of Minima Eclipsing Binaries by BBSAG Observers
Not Available
|
163. List of Minima Timings of Eclipsing Binaries by BBSAG Observers
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
|
CCD Minima for Selected Eclipsing Binaries in 2003
Not Available
|
162-nd List of Minima Timings of Eclipsing Binaries by BBSAG Observers
Not Available
|
Archive of Photometric Plates Obtained at Cluj Astronomical Observatory
The archive of photometric plates obtained at the AstronomicalObservatory of Cluj in the period 1952-1974 is presented. The plateinventory is made within the framework of the Wide-Field Plate Databaseproject. The plates were taken in the regions around 110 variable stars(eclipsing variables and RR Lyrae-type stars), as well as in somecomparison stars regions.
|
Minima of binary stars
Not Available
|
Light curve and physical parameters of the Algol-type binary TW Cas
Not Available
|
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.
|
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.
|
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.
|
AV Hydrae: a near-contact semi-detached binary with possible mass and angular momentum loss.
Not Available
|
Changes in the orbital period of the near-contact binary BF Vir.
Not Available
|
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.
|
The near-contact binary system RU Ursae Minoris
Not Available
|
A comparison of accurate absolute parameters of Algol systems with recent evolutionary models.
We have compiled a list of nine Algol-type binary stars (Algols) forwhich the observed absolute parameters are based on a self-consistentsolution of both the light curve(s) and radial velocity curves for bothcomponents, including the effects of non-Keplerian distortions. Theproperties of these systems are reviewed in the light of recentevolutionary models. We have been able to estimate initial mass ratiosfor 5 systems and to show that angular momentum loss via a magneticstellar wind is an important factor in the evolution of all the systems.We conclude that there is a lack of suitable evolutionary models forAlgols, particularly those of lower mass.
|
The absolute parameters of the Algol-type binary star AF Geminorum.
We present a spectroscopic orbit for both components of the Algol-typeeclipsing binary star AF Gem based on radial velocity measurements from17 CCD spectra using the cross-correlation technique. We find:(a_1_+a_2_)sin i=8.03+/-0.11Rsun_,m_1_sin^3^i=3.36+/-0.11Msun_,m_2_sin^3^i=1.15+/-0.04Msun_, m_1_/m_2_=2.92+/-0.07. This isthe first direct measurement of the mass ratio for this system. Theradial velocity measurements for the cool component vary peculiarly andthis is tentatively explained as a combination of chromospheric activityand non-synchronous rotation. We also present new solutions to the UBVlight curves of Chambliss (1982) using our new spectroscopic orbit tofix the mass ratio and to derive absolute parameters for bothcomponents. These absolute parameters have been used to applycorrections for non-Keplerian effects to the spectroscopic orbit. Theabsolute parameters of the system are found to be:M_1_=3.37+/-0.11Msun_, M_2_=1.155+/-0.04Msun_, R_1_=2.61+/-0.06Rsun_, R _2_=2.32+/-0.04Rsun_,log(L_1_/Lsun_)= 1.78+/-0.09, log(L_2_/Lsun_)=0.75+/-0.03. A comparison of AF Gem with the non-conservative case Bevolution models of De Greve (1993) suggests that the system evolvedfrom an initial mass ratio nearer to 0.6 than 0.9, and that perhaps moreangular momentum has been lost than has been assumed in the models.
|
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.
|
A Catalogue of Classical Evolved Algol-Type Binary Candidate Stars
Not Available
|
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).
|
AF Geminorum - an eclipsing triple star
AF Gem is an Algol-type eclipsing binary with a period of 1.2435 days.The period is found to have decreased slightly over the years that thisobject has been under observation. Approximately 800 observations in UBVhave been analyzed by the Wood (1972) method, and orbital elements havebeen obtained. The primary eclipse is a transit, and the eclipses arepartial. The spectral types of the components are estimated to be B9 Vand G0 IV. AF Gem has a faint visual companion situated about 2 arcsecfrom the eclipsing pair. It is most probable that this star is a memberof the system.
|
Periodic Ephemerides for 49 Eclipsing Binary-Star Systems
Abstract image available at:http://adsabs.harvard.edu/abs/1982PASP...94..485R
|
New ephemerides for 120 eclipsing binary stars
Abstract image available at:http://adsabs.harvard.edu/abs/1980ApJS...44..241M
|
Visual minima of eclipsing variables
Not Available
|
A catalogue of parameters for eclipsing binaries
Not Available
|
