The Proposed Quadruple System SZ Herculis: Revised LITE Model and Orbital Stability Study
In a recent study, Lee et al. presented new photometric follow-up timingobservations of the semidetached binary system SZ Herculis and proposedthe existence of two hierarchical cirumbinary companions. Based on thelight-travel time effect, the two low-mass M-dwarf companions are foundto orbit the binary pair on moderate to high eccentric orbits. Thederived periods of these two companions are close to a 2:1 mean-motionorbital resonance. We have studied the stability of the system using theosculating orbital elements as presented by Lee et al. Results indicatean orbit-crossing architecture exhibiting short-term dynamicalinstabilities leading to the escape of one of the proposed companions.We have examined the system's underlying model parameter space byfollowing a Monte Carlo approach and found an improved fit to the timingdata. A study of the stability of our best-fitting orbits also indicatesthat the proposed system is generally unstable. If the observedanomalous timing variations of the binary period is due to additionalcircumbinary companions, then the resulting system should exhibit along-term stable orbital configuration much different from the orbitssuggested by Lee et al. We, therefore, suggest that based onNewtonian-dynamical considerations, the proposed quadruple system cannotexist. To uncover the true nature of the observed period variations ofthis system, we recommend future photometric follow-up observations thatcould further constrain eclipse-timing variations and/or refinelight-travel time models.
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The Algol System SZ Herculis: Physical Nature and Orbital Behavior
Multiband CCD photometric observations of SZ Her were obtained between2008 February and May. The light curve was completely covered andindicated a significant temperature difference between both components.The light-curve synthesis presented in this paper indicates that theeclipsing binary is a classical Algol-type system with parameters of q =0.472, i = 87fdg57, and ?(T 1 - T 2) = 2381K; the primary component fills approximately 77% of its limiting lobeand is slightly larger than the lobe-filling secondary component. Morethan 1100 times of minimum light spanning more than a century were usedto study an orbital behavior of the binary system. It was found that theorbital period of SZ Her varied due to a combination of two periodicvariations with cycle lengths of P 3 = 85.8 yr and P4 = 42.5 yr and semi-amplitudes of K 3 = 0.013days and K 4 = 0.007 days, respectively. The most reasonableexplanation for these variations is a pair of light-time effects drivenby the possible existence of two M-type companions with minimum massesof M 3 = 0.22 M &sun; and M 4 = 0.19M &sun; that are located close to the 2:1 mean motionresonance. If two additional bodies exist, then the overall dynamics ofthe multiple system may provide a significant clue to the formation andevolution of the eclipsing pair.
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Random forest automated supervised classification of Hipparcos periodic variable stars
We present an evaluation of the performance of an automatedclassification of the Hipparcos periodic variable stars into 26 types.The sub-sample with the most reliable variability types available in theliterature is used to train supervised algorithms to characterize thetype dependencies on a number of attributes. The most useful attributesevaluated with the random forest methodology include, in decreasingorder of importance, the period, the amplitude, the V-I colour index,the absolute magnitude, the residual around the folded light-curvemodel, the magnitude distribution skewness and the amplitude of thesecond harmonic of the Fourier series model relative to that of thefundamental frequency. Random forests and a multi-stage scheme involvingBayesian network and Gaussian mixture methods lead to statisticallyequivalent results. In standard 10-fold cross-validation (CV)experiments, the rate of correct classification is between 90 and 100per cent, depending on the variability type. The main mis-classificationcases, up to a rate of about 10 per cent, arise due to confusion betweenSPB and ACV blue variables and between eclipsing binaries, ellipsoidalvariables and other variability types. Our training set and thepredicted types for the other Hipparcos periodic stars are availableonline.
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Recent Minima of 144 Eclipsing Binary Stars
This paper continues the publication of times of minima for eclipsingbinary stars from observations reported to the AAVSO Eclipsing BinarySection. Times of minima from observations made from March 2010 throughSeptember 2010, along with a few unpublished times of minima from olderdata, are presented.
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Do Eclipsing Variable Stars Show Random Cycle-to-cycle Period Fluctuations?
AAVSO observers and others have measured the times of minima of hundredsof eclipsing binaries over many decades. These times can be used toconstruct (O-C) diagrams that can be used to refine the periods of thestars, and to look for changes or fluctuations in the periods. We haveapplied the Eddington-Plakidis (1929) model to the (O-C) data on 100stars in the AAVSO-Eclipsing Binary Program, to determine whether the(O-C) diagrams can be explained by the cumulative effect of random,cycle-to-cycle fluctuations in period. The stars can be divided intothree groups: 25-35% showing (O-C) fluctuations due only to measurementerrors; 40-50% showing small, random cycle-to-cycle period fluctuations(typically a few times 10^4 of a cycle), and 20-30% showing (O-C)variations which do not fit the Eddington-Plakidis model and thereforecannot be explained by the accumulation of random fluctuations. Wediscuss possible explanations for these three groups.
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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.
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BAV-Results of Observations - Photoelectric minima of selected eclipsing binaries and maxima of pulsating stars.
Not Available
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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.
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Recent Minima of 161 Eclipsing Binary Stars
This paper continues the publication of times of minima for eclipsingbinary stars from observations reported to the AAVSO Eclipsing BinarySection. Times of minima from observations made from March 2009 throughAugust 2009, along with a few unpublished times of minima from olderdata, are presented.
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BAV-Results of Observations - Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
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Survey of Candidate Pulsating Eclipsing Binaries - I
Initial results from a photometric survey of stars selected from thelist of eclipsing binaries that may contain a pulsating component bySoydugan et al. (2006) are reported. A minimum of two nights of CCDobservations with V and/or B filters of each of the 35 stars from thislist was collected. Of the 35 stars stud- ied, a pulsating component wasdetected in three of the systems. Pulsations were also serendiptiouslydetected in the eclipsing binary RR Leporis, which is not on thecandidate list.
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BAV-Results of Observations - Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
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BAV-Results of observations - Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
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Recent Minima of 184 Eclipsing Binary Stars
This paper continues the publication of times of minima for eclipsingbinary stars from observations reported to the AAVSO Eclipsing BinaryCommittee. Times of minima from observations made from March 2008through August 2008 are presented.
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Recent Minima of 155 Eclipsing Binary Stars
The AAVSO's publication of times of minima for eclipsing binary stars has shifted from the recent publication series, Observed Minima Timings of Eclipsing Binaries, Number 1-12, back to the JAAVSO. Times of minima fromobservations made in the past eight months are presented. New lightelements for AC CMi have been calculated from recent AAVSO observations:Min(JD) = 2451978.7504 + 0.867216691 E± 0.0004 ± 0.00000024
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B.R.N.O. Times of minima
Not Available
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Possible third body effects in the period changes of four Algol binaries: RY Aqr, SZ Her, RV Lyr and V913 Oph
An investigation of the orbital period changes of the neglectedeclipsing binaries, RY Aqr, SZ Her, RV Lyr and V913 Oph, is presentedbased on all published minima times. Although the explanation ofmagnetic activity on the surface of the secondaries of the studiedAlgols is still open, the preferred light-time effect due to the unseencomponents around the systems seems more plausible in explaining thetilted sinusoidal variations with relatively high-amplitudes. Theminimal mass values of possible tertiary components have been estimatedto be about 1.06, 0.25, 0.78 and 2.85 M_? for RY Aqr, SZ Her, RVLyr and V913 Oph, respectively and the results indicate that theircontributions to the total light of the eclipsing pairs are measurablewith high accuracy photometric and spectroscopic data, if they exist.Applegate's (1992) model has been discussed as an alternative mechanismassuming that the cooler components have magnetic cycles. It is foundthat the model parameters of RY Aqr and V913 Oph are consistent with therequired values in Applegate's model. In addition to the first detailedorbital study on these systems, a statistical survey on the character ofthe O-C variations of classical Algols has revealed that about 50percent of the systems show cyclic behavior. This means that thepresence of possible third bodies around classical Algols should betested with careful analysis using new data.
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B.R.N.O. Contributions #34
Not Available
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Photoelectric Minima of Some Eclipsing Binary Stars
We present 119 minima times of 47 eclipsing binaries.
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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.
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Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
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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.
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New CCD Times of Minima of Eclipsing Binary Systems
We present a total of 208 CCD timings for 103 eclipsing binaries.
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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.
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Minima Kurt Locher 2004-2005
Minima observed 2004..2005 by Kurt Locher visually, not accepted by IBVSas part of BBSAG Bulletin.
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CCD Observations of Times of Minima of Eclipsing Binaries
120 minima timings are reported for 39 E. B. systems observed from 2002to 2005 with the Rigel telescope at Winer Observatory. The timings weredetermined using a folded light curve analysis of light curves derivedfrom CCD images. Typical timing uncertainties were 30-60 sec.
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CCD Minima for Selected Eclipsing Binaries in 2004
Not Available
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163. List of Minima Timings of Eclipsing Binaries by BBSAG Observers
Not Available
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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/.
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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
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INHABITED SKY
