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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BAV-Results of observations - Photoelectric minima of selected eclipsing binaries and maxima of pulsating stars.
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Algol-Type Eclipsing Binaries with ? Scuti-Type Pulsating Components: IV Cas
We present the results of photometric and spectroscopic observations ofthe Algol-type eclipsing binary with a ? Scuti-type pulsatingcomponent IV Cas. This is the first comprehensive study of the absoluteproperties of the binary system and also of the pulsationcharacteristics of the primary component. The high-resolutionspectroscopic data have enabled us to estimate the atmosphericparameters of the primary component. Our BV light-curve analysis hasrevealed that the binary system is in a semidetached configuration,consisting of a detached main-sequence primary of spectral type A3 andan evolved secondary of early-K spectral type, which fills its innerRoche lobe completely. We found that the two components are too close toeach other to form an accretion disk. Spectroscopic results without anemission feature supported the nonexistence of noticeable disk. Therotation of the primary turned out to be nearly synchronized with therevolution, giving a hint that IV Cas is in the middle or late stage ofthe slow mass transfer phase. This coincides well with a slow masstransfer rate deduced from the fact that there was no secular parabolicchange of the orbital period for the past ˜100 yr. Using residualssubtracted from synthetic eclipsing curves of photometric data, weexamined the pulsation properties of the primary component. Amultiple-frequency analysis was applied to the residuals in theout-of-primary eclipsing phases and this resulted in the detection offour frequencies: f=32.69236 cycles day, f=36.65999 cycles day,f=20.71649 cycles day, and f=30.66072 cycles day. We tentativelyidentified their pulsation modes on the basis of pulsation constants,frequency spacing, mode visibility in eclipsing binaries, phasedifferences, and amplitude ratios; f and f (or f and f) appeared to berotational splitting frequencies. The observational properties of IV Caswell matched the empirical relations for Algol-type eclipsing binarieswith ? Scuti-type pulsating components.
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? Sct-type pulsations in eclipsing binary systems: Y Cam
We present the results of a three-continent multisite photometriccampaign carried out on the Algol-type eclipsing binary system Y Cam, inwhich the primary component is a multiperiodic ? Sct-typepulsator. The observations consist of 86 nights and more than 450 h ofuseful data collected mainly during the Northern winter 2002-2003. Thismeans that this is the most extensive time series for such kind ofsystems obtained so far. These observations were collected mostly in theJohnson V filter, but they also include, for the first time, nearlycomplete binary light curves in simultaneous Strömgren uvby filterstogether with a few Crawford H? data obtained around the orbitalphase of the first quadrature. A detailed photometric analysis ispresented for both binarity and pulsation. The results indicate asemidetached system with the secondary filling its Roche lobe. Nosignificant contribution from a third body is found. The residuals fromthe computed binary solution were then used to investigate thepulsational content of the primary component. The frequency analysis ofthe out-of-primary-eclipse data leads to a set of eight significant andindependent pulsational peaks in a well-defined region of the frequencydomain. This means that this is the largest set of excited modesdiscovered so far in the pulsating component of such kind of systems.The possibility of aliasing problems during the present run orshort-term time-scale amplitude variations in some of them wasinvestigated with null results. Indeed the results indicate thatf1 and f3 form a frequency doublet with a beatperiod of Pbeat = 17.065 d. Our results confirm thefrequencies already detected by earlier authors and show the presence ofsome additional significant peaks. The observed amplitudes during thepresent run are also consistent with those derived from older data sets.We perform a preliminary mode identification for most of the frequencieson the basis of the collected multicolour photometry, the observedfrequency spacings and the mode visibility in eclipsing binaries.
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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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B.R.N.O. Contributions #36, Times of minima
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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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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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The first high-amplitude ? Scuti star in an eclipsing binary system
We report the discovery of the first high-amplitude ? Scuti starin an eclipsing binary, which we have designated UNSW-V-500. The systemis an Algol-type semi-detached eclipsing binary of maximum brightness V= 12.52 mag. A best-fitting solution to the binary light curve and tworadial velocity curves is derived using the Wilson-Devinney code. Weidentify a late-A spectral-type primary component of mass 1.49 +/-0.02Msolar and a late-K spectral-type secondary of mass 0.33+/- 0.02Msolar, with an inclination of , and a period of5.3504751 +/- 0.0000006 d. A Fourier analysis of the residuals from thissolution is performed using PERIOD04 to investigate the ? Scutipulsations. We detect a single pulsation frequency of f1 =13.621 +/- 0.015 cd-1, and it appears that this is the firstovertone radial mode frequency. This system provides the firstopportunity to measure the dynamical mass for a star of this variabletype; previously, masses have been derived from stellar evolution andpulsation models.
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B.R.N.O. Contributions #34
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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.
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Pulsational frequencies of the eclipsing δ Scuti star HD 172189. Results of the STEPHI XIII campaign
Context: The eclipsing δ Scuti star HD 172189is a probable member of the open cluster IC 4756 anda promising candidate target for the CoRoT mission. Aims: The detectionof pulsation modes is the first step in the asteroseismological study ofthe star. Further, the calculation of the orbital parameters of thebinary system allows us to make a dynamical determination of the mass ofthe star, which works as an important constraint to test and calibratethe asteroseismological models. Methods: We performed a detailedfrequency analysis of 210 hours of photometric data of HD172189 obtained from the STEPHI XIII campaign. Results: Wehave identified six pulsation frequencies with a confidence level of 99%and a seventh with a 65% confidence level of 65%, in the range between100-300 μHz. In addiction, three eclipses were observed during thecampaign, allowing us to improve the determination of the orbital periodof the system.Table 1 is only available in electronic form at http://www.aanda.org
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Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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A photometric study of the Algol-type binary AB Cas
We present new photoelectric observations of the eclipsing binary systemAB Cas, together with an analysis of the light curves. Using theavailable times of light minimum reported in the literature togetherwith our own minima, period changes are monitored, and the possiblethird-body parameters are obtained. The absolute properties of thesystem and the delta-Scuti behavior of the primary are also discussed.
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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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An Algol type binary with a δ Scuti component: RZ Cassiopeiae revisited
We present new BV photometry and spectroscopic observations of RZCassiopeiae. The light and radial velocity curves were formed by the newobservations which have been analyzed simultaneously by using theWilson-Dewinney code. The non-synchronous rotational velocityv1sin i = 76 ± 6 km s-1, deduced for theprimary component from the new spectroscopic observations, was alsoincorporated in the analysis. A time-series analysis of the residuallight curves revealed the multi-periodic pulsations of the primarycomponent of RZ Cas. The main peak in the frequency spectrum wasobserved at about 64.197 c d-1 in both B and V bands. Thepulsational constant was calculated to be 0.0116 days. This valuecorresponds to high overtones (n˜6) of non-radial modeoscillations. We find significant changes in the pulsational amplitudeof the primary component from year to year. The peak-to-peak pulsationalamplitude of the main frequency displays a decrease from 0.013 m in 2000to 0.002 m in 2001 and thereafter we have found an increase again in theamplitude to 0.01 m in the year 2002. We propose the mass transfer fromthe cool secondary to the pulsating primary as a possible explanationfor such remarkable changes in the pulsational behavior of the primarycomponent.
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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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Modelling eclipsing binaries with pulsating components: Phase dependence of observed pulsation amplitudes
We investigate the phase dependence of the light variations due topulsations, as modulated with light variations due to the eclipses. Thestudy is based, both on a simplified model and on the rigorous lightcurve (LC) synthesis software of Wilson and Devinney. We model AB Cas asa prototype, using both of these approaches. The phase dependence of thedifferential light variations for total systems is also discussed .
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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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Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veranderliche Sterne e.V.
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New Times of Minima of Some Eclipsing Binary Stars
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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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Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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