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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A comprehensive photometric study of the Algol-type eclipsing binary: BG Pegasi
This study presents new photometric observations of classical Algol typebinary BG Peg with a ? Scuti component. The light curve modelingwas provided with the physical parameters of the component stars in theBG Peg system for the first time. After modeling light curves in B and Vfilters, the eclipse and proximity effects were removed from the lightcurve to analyze intrinsic variations caused by the hotter component ofthe system. Frequency analysis of the residuals light represents themulti-mode pulsation of the more massive component of the BG Peg systemat periods of 0.039 and 0.047 days. Two frequencies could be associatedwith non-radial (l = 2) modes. The total amplitude of the pulsationalvariability in the V light curve was found to be about 0.045 mag. Thelong-term orbital period variation of the system was also investigatedfor the first time. The O-C analysis indicates periodic variationsuperimposed on a downward parabola. The secular period variation meansthat the orbital period of the system is decreasing at a rate of-5.5 seconds per century, probably due to the magnetic activity ofthe cooler component. The tilted sinusoidal O-C variation may be causedby the gravitational effect of an unseen component around the system.
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A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun
Traditionally, runaway stars are O- and B-type stars with large peculiarvelocities. We would like to extend this definition to young stars (upto ?50 Myr) of any spectral type and to identify those present in theHipparcos catalogue by applying different selection criteria, such aspeculiar space velocities or peculiar one-dimensional velocities.Runaway stars are important for studying the evolution of multiple starsystems or star clusters, as well as for identifying the origins ofneutron stars. We compile the distances, proper motions, spectral types,luminosity classes, V magnitudes and B-V colours, and we utilizeevolutionary models from different authors to obtain star ages. We studya sample of 7663 young Hipparcos stars within 3 kpc from the Sun. Theradial velocities are obtained from the literature. We investigate thedistributions of the peculiar spatial velocity and the peculiar radialvelocity as well as the peculiar tangential velocity and itsone-dimensional components and we obtain runaway star probabilities foreach star in the sample. In addition, we look for stars that aresituated outside any OB association or OB cluster and the Galactic planeas well as stars for which the velocity vector points away from themedian velocity vector of neighbouring stars or the surrounding local OBassociation/cluster (although the absolute velocity might be small). Wefind a total of 2547 runaway star candidates (with a contamination ofnormal Population I stars of 20 per cent at most). Thus, aftersubtracting these 20 per cent, the runaway frequency among young starsis about 27 per cent. We compile a catalogue of runaway stars, which isavailable via VizieR.
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The Banana Project. III. Spin-Orbit Alignment in the Long-period Eclipsing Binary NY Cephei
Binaries are not always neatly aligned. Previous observations of the DIHer system showed that the spin axes of both stars are highly inclinedwith respect to one another and the orbital axis. Here, we report on ameasurement of the spin-axis orientation of the primary star of the NYCep system, which is similar to DI Her in many respects: it features twoyoung early-type stars (~6 Myr, B0.5V+B2V), in an eccentric andrelatively long-period orbit (e = 0.48, P = 15fd3). The sky projectionsof the rotation vector and the spin vector are well aligned(?p = 2° ± 4°), in strong contrast to DIHer. Although no convincing explanation has yet been given for themisalignment of DI Her, our results show that the phenomenon is notuniversal, and that a successful theory will need to account for thedifferent outcome in the case of NY Cep.Based on observations made with Sophie, a high-resolution échellespectrograph on the 1.93 m telescope of the Observatoire deHaute-Provence.
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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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Recent Minima of 154 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 September 2008through February 2009 are presented.
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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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B.R.N.O. Times of minima
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Discovery of Short-periodic Pulsating Component in the Eclipsing Binary Y Leonis
We report the discovery of short-periodic oscillations of the primarycomponent of the Algol binary system Y Leonis. From our preliminaryresults it is a delta Scuti star and probably a new member of oEA group.
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Aus den IBVS.
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B.R.N.O. Contributions #34
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New Times of Minima of Some Eclipsing Binary Stars
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CCD Times of Minima of Selected Eclipsing Binaries
374 CCD minima observations of 187 eclipsing binaries are presented. Theobserved stars were chosen mainly from catalogue BRKA of observingprogramme of Variable Star Section of CAS.
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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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New Times of Minima of Eclipsing Binary Systems and of Maximum of SXPHE Type Stars
We present 64 photoelectric minima observations of 31 eclipsingbinaries. We also report three new times of maxima of three SXPHE typepulsating stars.
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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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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.
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CCD Minima for Selected Eclipsing Binaries in 2005
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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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Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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New Times of Minima of Eclipsing Binary Stars
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CCD Minima for Selected Eclipsing Binaries in 2004
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Precise CCD Times of Minima of Selected Eclipsing Binaries
We present 50 CCD minima timings for 42 eclipsing binaries obtained atOndrejov observatory during 2002-2003.
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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.
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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.
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Observational study of interacting binary stars
We present a progress report on the results obtained from photometricand spectroscopic observations of the interacting binary stars SW Cyg,RR Dra, Y Leo, and SW Lyn in our Galaxy. Analogous studies could beeventually carried out for interacting binaries in the Local Groupgalaxies. From this study we note the significant Hα line profilevariations in spectra of SW Cyg taken at two different orbital phases.
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163. List of Minima Timings of Eclipsing Binaries by BBSAG Observers
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INHABITED SKY
