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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.
| 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.
| Turning Back the Clock: Inferring the History of the Eight O'clock Arc
We present the results from an optical and near-infrared (NIR)spectroscopic study of the ultraviolet-luminous z = 2.73 galaxy, the 8o'clock arc. Due to gravitational lensing, this galaxy is magnified by afactor of ? > 10, allowing in-depth measurements which are usuallyunfeasible at such redshifts. In the optical spectra, we measured thesystemic redshift of the galaxy, z = 2.7322± 0.0012, usingstellar photospheric lines. This differs from the redshift of absorptionlines in the interstellar medium, z = 2.7302 ± 0.0006, implyinggas outflows on the order of 160 km s-1. With H- and K-bandNIR spectra, we have measured nebular emission lines of H?,H?, H?, [N II], and [O III], which have a redshift z = 2.7333± 0.0001, consistent with the derived systemic redshift. From theBalmer decrement, we measured the dust extinction in this galaxy to be A5500 = 1.17 ± 36 mag. Correcting the H? lineflux for dust extinction as well as the assumed lensing factor, wemeasure a star formation rate (SFR) of ~270 M sunyr-1, which is higher than ~85% of star-forming galaxies at z~ 2-3. Using combinations of all detected emission lines, we find thatthe 8 o'clock arc has a gas-phase metallicity of ~0.8 Z sun,showing that enrichment at high redshift is not rare, even in blue,star-forming galaxies. Studying spectra from two of the arc componentsseparately, we find that one component dominates both the dustextinction and SFR, although the metallicities between the twocomponents are similar. We derive the mass via stellar populationmodeling, and find that the arc has a total stellar mass of ~4.2 ×1011 M sun, which falls on the mass-metallicityrelation at z ~ 2. Finally, we estimate the total gas mass, and find itto be only ~12% of the stellar mass, implying that the 8 o'clock arc islikely nearing the end of a starburst.Based partly on observations obtained at the Gemini Observatory, whichis operated by the Association of Universities for Research inAstronomy, Inc., under a cooperative agreement with the NSF on behalf ofthe Gemini partnership: the National Science Foundation (USA), theScience and Technology Facilities Council (UK), the National ResearchCouncil (Canada), CONICYT (Chile), the Australian Research Council(Australia), Ministerio da Ciencia e Tecnologia (Brazil), and SECYT(Argentina). Some of the data presented herein were obtained at the W.M.Keck Observatory, which is operated as a scientific partnership amongthe California Institute of Technology, the University of California,and the National Aeronautics and Space Administration. The Observatorywas made possible by the generous financial support of the W. M. KeckFoundation.
| Evolutionary Status of RV Trianguli and its Related Algol-Type Binaries
We present CCD photometry for the Algol-type binary RV Trianguliobserved during three nights in 2007 November. The photometric solutionwas derived from our VR observations by using the Wilson-Devinnyprogram. The results indicated that RV Tri is a semidetached binary witha mass ratio of q = 0.306 (± 0.005). Based on 236 light minimumtimes, the orbital period change of RV Tri was analyzed in detail. Wediscovered that a secular decrease exists with two cyclic variations.The long-term period decreases at a rate of dP/dt = -6.07 ×10-8days yr-1, which may be due tomass and angular momentum loss. Two cyclic variations (i.e., P3 = 25.34 yr and A 3 = 0fd0029, and P 4= 10.30 yr and A 4 = 0fd0026) may be attributed to the unseenthird and fourth bodies, respectively, which can be weakly identified bythe photometric solution. If the existence of the two additional bodiesis true, this binary may be a quadruple star. From 22 Algol binarysystems with orbital periods decreasing, the relations of P -dP/dt and P - f were determined. With the orbital period decrease,dP/dt also decreases, indicating that mass and angular momentum losswill become slower. However, the fill-out factor of the primary f willincrease as the period decreases, which will finally result in theprimary filling its Roche lobe. Therefore, this kind of binary willevolve into a contact configuration.
| 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.
| 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
| 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.
| 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.
| The Near-Contact Binary RU Ursae Minoris
The near-contact binary RU UMi with an F0-type primary and a K-typesecondary was observed in 2003. With the latest version of theWilson-Devinney code, the photometric elements were computed. Theresults reveal that RU UMi is a semi-detached system with the secondarycomponent filling its Roche lobe, which should lead to an increase ofthe period for conservative mass transfer between the two components.However, an orbital period analysis shows that the orbital period ofthis system undergoes a continuous decrease at a rate ofdP/dt=-1.72×10-8d yr-1. Therefore, thecontinuous period decrease may demonstrate that the system isnonconservative. This can result from a combined effect of mass transferfrom the secondary component to the primary one and mass and angularmomentum loss from the system. With the secular mass and angularmomentum losses, RU UMi may evolve from the present short-periodnear-contact system into an A-type contact binary.
| 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.
| Minima Kurt Locher 2004-2005
Minima observed 2004..2005 by Kurt Locher visually, not accepted by IBVSas part of BBSAG Bulletin.
| 163. List of Minima Timings of Eclipsing Binaries by BBSAG Observers
Not Available
| 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 Two Algol-Type Eclipsing Binary Systems: TY Pegasi and X Trianguli
O-C curves of two EA-type eclipsing binaries, TY Peg and X Tri, areformed and studied in detail based on all available times of lightminimum. For TY Peg, it was discovered that the general trend of the O-Ccurve showed a downward parabolic variation, which indicates a secularperiod decrease with rate at dP/dt=-1.16×10-6 daysyr-1. When the secular decrease is removed from the O-Ccurve, the residuals can be described by several linear ephemerides,suggesting several sudden period jumps. For the other one, X Tri, it isfound that the general O-C trend also indicates a secular perioddecrease (dP/dt=-1.42×10-7 days yr-1), andseveral irregular period jumps are found to superpose on the long-timeperiod decrease. This kind of period change, irregular sudden jumpssuperposed on secular decrease, is typical for many other Algol-typebinary systems such as TU Her, UU And, Z Per, Y Psc, BO Mon, FH Ori, RTPer, and TX UMa. The period changes of these systems may be caused byorbital angular momentum loss via variable magnetic coupling and gravitycoupling between the components.
| 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
| 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.
| Interaction of Eclipsing Binaries with their Environment
The interaction of eclipsing binary star systems with the mass around(in the form of star, planet, envelope or disk) affects the orbitalperiod of these systems. Thus, the long-term orbital period changes ofeclipsing binaries which can be deduced by using the observed times ofeclipse minima provide a good tool in understanding the interaction ofeclipsing binaries with their environment. In the present contributionmany examples of the orbital period changes of different eclipsingbinaries are presented and interpreted in terms of the interaction withtheir environment.
| Revised Eclipse Prediction Elements for Eight Eclipsing Binary Stars
Evaluation of recently published times of minima of eight eclipsingbinaries determined by AAVSO observers reveals significant deviationsfrom the elements listed in the General Catalogue of Variable Stars(GCVS). New elements for MM Cas, SW Cyg, TU Her, EQ Ori, FL Ori, TY Peg,ST Per, and BO Vul are given here.
| Radio continuum emission from stars: a catalogue update.
An updated version of my catalogue of radio stars is presented. Somestatistics and availability are discussed.
| Statistical investigation of chemically peculiar stars. VI. Eclipsing binaries.
Not Available
| A Catalogue of Classical Evolved Algol-Type Binary Candidate Stars
Not Available
| Loss of orbital angular momentum and period changes in ALGOLS
Initial values of orbital period have been computed for 50 Algolbinaries using previously published relations and then compared withobservational data. The calculations assumed an initial mass ratio of1.2, which is the average mass ratio for unevolved binaries. Thecomputed orbital period ratios are compared with the observed trend ofperiod variation in Algol-type binaries. It is concluded that theagreement between theory and observational data is much better when anonconservative approach to evolution is adopted.
| 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).
| Evolution in semi-detached binary systems
The evolutionary process of semidetached binary systems is considered onthe basis of nonconservation of orbital angular momentum. Initialperiods for 54 Algol-type binaries are calculated using relations givenby Chaubey (1979) and assuming an initial mass ratio of 1.2 (the averagemass ratio for unevolved binaries). It is found that the semidetachedbinary systems follow Type B evolution.
| A catalogue of parameters for eclipsing binaries
Not Available
| Photoelectrically-Neglected Eclipsing Binaries
Not Available
| Loss of orbital angular momentum in close binary systems during their evolution
A total 91 binary systems of systemic mass less than 6.5 M0 have beenstudied. It is found that binary systems obey the relation: log H = C -1.8 log M where C is constant having values - 1.18, -2.12 and -2.27respectively for detached, semi-detached and contact binary systems. Itis inferred that during evolution, the systemic orbital angular momentumdecreases
| Period-mass ratio relations for eclipsing binaries with periods not exceeding 5 days
A study of mass ratio (the ratio of the mass of the secondary to that ofthe primary component) versus period in eclipsing binaries is presented.The investigation, which focuses on binaries with periods no greaterthan 5.0 days, considers 98 eclipsing binary systems. The resultsprovide an aid for determining the mass ratios of semidetached binarysystems without resort to spectroscopic observations.
| Visual minima of eclipsing binaries from Cracow observations 1920-1950.
Not Available
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