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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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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The Near-contact Binary RZ Draconis with Two Possible Light-time Orbits
We present new multicolor photometry for RZ Draconis, observed in 2009at the Xinglong Station of the National Astronomical Observatories ofChina. By using the updated version of the Wilson-Devinney Code, thephotometric-spectroscopic elements were deduced from new photometricobservations and published radial velocity data. The mass ratio andorbital inclination are q = 0.375(±0.002) and i =84fdg60(±0fdg13), respectively. The fill-out factor of theprimary is f = 98.3%, implying that RZ Dra is an Algol-like near-contactbinary. Based on 683 light minimum times from 1907 to 2009, the orbitalperiod change was investigated in detail. From the O - C curve, it isdiscovered that two quasi-sinusoidal variations may exist (i.e., P3 = 75.62(±2.20) yr and P 4 =27.59(±0.10) yr), which likely result from light-time effects viathe presence of two additional bodies. In a coplanar orbit with thebinary system, the third and fourth bodies may be low-mass drafts (i.e.,M 3 = 0.175 M sun and M 4 = 0.074 Msun). If this is true, RZ Dra may be a quadruple star. Theadditional body could extract angular momentum from the binary system,which may cause the orbit to shrink. With the orbit shrinking, theprimary may fill its Roche lobe and RZ Dra evolves into a contactconfiguration.
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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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BAV-Results of Observations - Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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Automated Variable Star Classification Using the Northern Sky Variability Survey
We have identified 4659 variable objects in the Northern Sky VariabilitySurvey. We have classified each of these objects into one of the fivevariable star classes: (1) Algol/β Lyr systems includingsemidetached, and detached eclipsing binaries, (2) W Ursae Majorisovercontact and ellipsoidal variables, (3) long-period variables such asCepheid and Mira-type objects, (4) RR Lyr pulsating variables, and (5)short-period variables including δ Scuti stars. All the candidateshave outside of eclipse magnitudes of ~10-13. The primary classificationtool is the use of Fourier coefficients combined with period informationand light-curve properties to make the initial classification. Briefmanual inspection was done on all light curves to remove nonperiodicvariables that happened to slip through the process and to quantify anyerrors in the classification pipeline. We list the coordinates, period,Two Micron All Sky Survey colors, total amplitude variation, and anyprevious classification of the object. 548 objects previously identifiedas Algols in our previous paper are not included here.
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New Period Investigation of Algol-like Near-Contact Binary EG Cephei
The Algol-like Near Contact Binary EG Cephei was observed in 2008October. One new observed time of the secondary minimum was derived inBV(IR)c bands. It turns out that the times of minima atlonger wavelengths occur earlier than the shorter ones. All of theavailable eclipse times, including 735 epochs, spanning more than 100years were analyzed. A period oscillation with a period of35.8(±0.1)yr and an amplitude of about 0.0037(±0.0002)dwas found, while undergoing a secular increase at a rate of dP/dt = 3.4× 10-8 (±0.1)d yr-1. This continuousperiod increase may be caused by mass transfer from the secondarycomponent to the primary one on a thermal timescale, which is consistentwith the Algol-like semi-detached configuration of EG Cep. Combiningwith the spectroscopic and photometric results, we derived aconservative mass-transfer rate of this target, dM/dt = 3.0(±0.1)× 10-8Modotyr-1. The oscillationpart of the period variation may be the result of a light-time effectdue to the existence of a coplanar additional body with a mass ofM3 = 0.11Modot, and a corresponding radius ofa3 = 14AU. The presumed third body may play an important rolein the evolution of this system.
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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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BAV-Results of observations
This 62nd compilation contains the results of visual observations ofBAV-members from the years 2007 and 2008. Here we publish altogether 337minima and maxima of 201 eclipsing binaries, pulsating and eruptivestars. The data were acquired by 14 observers. The compilation containsalso one photographic- and two ccd-results.
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BAV-Results observations.
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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
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The First Multi-Color Photometric Study of the Near-Contact Binary as Serpentis
The first complete multi-color CCD photometric light curves of theeclipsing binary AS Ser were obtained over three nights in 2005. Usingthe latest Wilson-Devinney (WD) code, we computed the photometricelements of this system. It turns out that AS Ser is a near-contactbinary system with both components filling more than 99% of their Rochelobes. It belongs to a marginal contact binary system within theparameter uncertainties. The marginal characteristic of AS Ser revealsthat this target may be in a rare phase predicted by the thermalrelaxation oscillation (TRO) theory. The asymmetry of the light curvescan be explained by a dark spot on the secondary component, which isconsistent with its late-type nature. Combining all available times oflight minimum, we derived a new orbital period of AS Ser and found aperiodic oscillation varying within an amplitude of 0.0049 days and aperiod of 11.8 years. This period change may be the result of thelight-time effect due to a presumed tertiary component (M 3> 0.28M sun) or might result from magnetic activity cyclesof the two components.
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Times of Minima for Neglected Eclipsing Binaries 2006-2007
CCD minima observations of eclipsing binaries during 2006-2007 for anumber of neglected eclipsing binaries are presented.
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First Results of CCD and Photoelectric Photometry on Astronomical Observatory at Kolonica Saddle
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A Mechanism for Orbital Period Modulation and Irregular Orbital Period Variations in Close Binaries
Orbital period modulation is observed in many magnetically active closebinaries. It can be explained by magnetic connection between two stars.Magnetic connection produces weak force between the two stars. As themagnetic field varies periodically, the orbital period also showscyclical variations. The mechanism can also be used to explain irregularorbital period variations and orbital period jumps. The mean surfacemagnetic strength is calculated by using the Radia package, which isdedicated to 3D magnetostatics computation. On the basis of the results,a practical equation is given to calculate surface magnetic strength.
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B.R.N.O. Contributions #34
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Photoelectric Minima of Some Eclipsing Binary Stars
We present 51 minima times of 19 eclipsing binaries.
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Minima Times of Some Eclipsing Binary Stars
We present 48 pe and 14 CCD times of minima of selected eclipsingbinaries obtained from 1989 to 2007 at observatories in Turkey.
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New Minima Times of Selected Eclipsing Binaries
We present 169 CCD and photoelectric times of minima of selectedeclipsing binaries obtained from 2005 to 2007 at observatories inSlovakia
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Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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Photoelectric Minima of Some Eclipsing Binary Stars
We present 119 minima times of 47 eclipsing binaries.
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New Times of Minima of Some Eclipsing Binary Stars
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Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating 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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New Times of Minima of Some Eclipsing Binary Stars
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Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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Photoelectric Minima of Some Eclipsing Binary Stars
We present 70 minima times of 35 eclipsing binaries.
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Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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INHABITED SKY
