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Photometric Properties for Selected Algol-type Binaries. V. V1241 Tauri
We present new photometry for the eclipsing binary V1241 Tau, which wasobtained on six nights between 2011 December and 2012 January using the85 cm telescope at the Xinglong station of the National AstronomicalObservatories of China. By using the updated Wilson-Devinney code,photometric models with third lights were deduced from two sets of lightcurves. The result implies that V1241 Tau is an Algol-type near-contactbinary (NCB), whose mass ratio and filling-out of the primary are q =0.545 (± 0.003) and f 1 = 82.4% (± 0.2%),respectively. Based on all available times of minimum light spanningover 80 yr, the O - C curve of V1241 Tau appears to show aquasi-sinusoidal oscillation, i.e., a light-time orbit. The modulatedperiod and amplitude are P mod = 47.4 (± 1.7) yr and A= 0.0087 (± 0.0005) days, respectively. This kind of periodvariation may be more likely attributed to the light-time effect via apresence of an unseen third body. From an analysis of 23 Algol-type NCBswith EB-type light curves, we determine that the fill-out for theprimary f 1 will increase as the orbital period P decreases.With angular momentum loss, the orbit of the binary will shrink, whichcauses f 1 to increase. The primary component finally fillsits Roche lobe, and the binary evolves into contact configuration.Therefore, this kind of Algol-type NCB with EB-type light curves, suchas V1241 Tau, may be a progenitor of the A-type W UMa binary.
| Close binary system GO Cyg
In this study, we present long term photometric variations of the closebinary system GO Cyg. Modelling of the system shows that the primary isfilling Roche lobe and the secondary of the system is almost filling itsRoche lobe. The physical parameters of the system are M1 =3.0 ± 0.2M&sun;, M2 = 1.3 ±0.1M&sun;, R1 = 2.50 ±0.12R&sun;, R2 = 1.75 ±0.09R&sun;, L1 = 64 ± 9L&sun;,L2 = 4.9 ± 0.7L&sun;, and a = 5.5 ±0.3R&sun;. Our results show that GO Cyg is the most massivesystem near contact binary (NCB). Analysis of times of the minima showsa sinusoidal variation with a period of 92.3 ± 0.5 yr due to athird body whose mass is less than 2.3M&sun;. Finally aperiod variation rate of -1.4 × 10-9 d/yrhas been determined using all available light curves.
| First Modern Photometric Investigation of the Puzzling W UMa Type Close Binary System of TZ Bootis
New CCD photometric BVRI observations of the puzzling W UMa type binarystar, TZ Bootis, are presented from our observations in 2010. By usingthe updated version of the Wilson-Devinney code, the first modernphotometric solution is deduced from new photometric observations andpublished spectroscopic data. This low mass ratio binary turns out to bea deep overcontact system with f = 52% of A-subtype. A spot model hasbeen applied to fit the particular features of light curves. Based onour seven new light minimum times and all others compiled from theliterature over 70 yr, we studied the orbital period from the O-C curve.It is found that a 31.2 yr cyclic variation exists with an amplitude of0.033 days, overlaying a secular decrease at a rate of dP/dt = -2.1× 10-8 days yr-1. The cyclic period changemay indicate that TZ Boo is a triple or a quadruple system as confirmedfrom the published spectroscopic data. The long-term orbital perioddecrease is interpreted by mass transfer from the more to the lessmassive component and/or angular momentum loss by the magnetic breakingwhich would cause the overcontact degree to increase and finally thebinary will evolve into a single rapidly rotating star.
| 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.
| 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.
| 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.
| Recent Maxima of 56 Short Period Pulsating Stars
This paper contains times of maxima for 56 short period pulsating stars(primarily RR Lyrae and delta Scuti stars). This represents a portion ofthe CCD observations received by the AAVSO Short Period Pulsator (SPP)section in 2010 along with some earlier data.
| The near-contact binary star RZ Dra revisited
This paper presents the absolute parameters of RZ Dra. New CCDobservations were made at the Mt. Suhora Observatory in 2007. Twophotometric data sets (1990 BV and 2007 BVRI) were analysed using modernlight-curve synthesis methods. Large asymmetries in the light curves maybe explained in terms of a dark starspot on the primary component, an A6type star. Due to this magnetic activity, the primary component wouldappear to belong to the class of Ap-stars and would show small amplitudewith δ Scuti-type pulsations. With this in mind, a time-seriesanalysis of the residual light curves was made. However, we found noevidence of pulsation behaviour in RZ Dra. Combining the solutions ofour light curves and Rucinski et al. (2000)’s radial velocitycurves, the following absolute parameters of the components weredetermined: M1 = 1.63 ± 0.03 M&sun;,M2 = 0.70 ± 0.02 M&sun;, R1 =1.65 ± 0.02R&sun;, R2 = 1.15 ± 0.02R&sun;, L1 = 9.72 ± 0.30 L&sun;and L2 = 0.74 ± 0.10 L&sun;. The distanceto RZ Dra was calculated as 400 ± 25 pc, taking into accountinterstellar extinction. The orbital period of the system was studiedusing updated O-C information. It was found that the orbital periodvaried in its long-period sinusoidal form, superimposed on a downwardparabola. The parabolic term shows a secular period decrease at a slowrate of 0.06 ± 0.02 s per century and is explained by the massloss via magnetized wind of the Ap-star primary. The tilted sinusoidalform of the period variation may be considered as an apparent change andmay be interpreted in terms of the light-time effect due to the presenceof a third body.
| BAV-Results of observations - Photoelectric minima of selected eclipsing binaries and maxima of pulsating stars.
Not Available
| BAV-Results of Observations - Photoelectric minima of selected eclipsing binaries and maxima of pulsating stars.
Not Available
| Recent CCD Minima of 185 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 September 2009through February 2010 are presented.
| 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.
| 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.
| BAV-Results of Observations - Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| BAV-Results of Observations - Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| 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.
| 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.
| Observations of candidate oscillating eclipsing binaries and two newly discovered pulsating variables
CCD observations of 24 eclipsing binary systems with spectral typesranging between A0-F0, candidate for containing pulsating components,were obtained. Appropriate exposure times in one or more photometricfilters were used so that short-periodic pulsations could be detected.Their light curves were analyzed using the Period04 software in order tosearch for pulsational behaviour. Two new variable stars, namely GSC2673-1583 and GSC 3641-0359, were discov- ered as by-product during theobservations of eclipsing variables. The Fourier analysis of theobservations of each star, the dominant pulsation frequencies and thederived frequency spectra are also presented.
| BAV-Results of observations - Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| 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.
| B.R.N.O. Times of minima
Not Available
| 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.
| B.R.N.O. Contributions #34
Not Available
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| CCD Times of Minima of Some Eclipsing Binaries from the SAVS Sky Survey
We present CCD observations of minima of 18 eclipsing binaries observedby SAVS sky survey in year 2004 - 2007.
| 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.
| Contact Binaries with Additional Components. II. A Spectroscopic Search for Faint Tertiaries
It is unclear how very close binary stars form, given that during thepre-main-sequence phase the component stars would have been inside eachother. One hypothesis is that they formed farther apart but were broughtin closer after formation by gravitational interaction with a thirdmember of the system. If so, all close binaries should be members oftriple (or higher order) systems. As a test of this prediction, wepresent a search for the signature of third components in archivalspectra of close binaries. In our sample of 75 objects, 23 show evidencefor the presence of a third component, down to a detection limit oftertiary flux contributions of about 0.8% at 5200 Å (consideringonly contact and semidetached binaries, we find 20 out of 66). In ahomogeneous subset of 59 contact binaries, we are fairly confident thatthe 15 tertiaries we have detected are all tertiaries present with massratios 0.28<~M3/M12<~0.75 and implied outerperiods P<~106 days. We find that if the frequency oftertiaries were the same as that of binary companions to solar-typestars, one would expect to detect about 12 tertiaries. In contrast, ifall contact binaries were in triple systems, one would expect about 20.Thus, our results are not conclusive but are sufficiently suggestive towarrant further studies.
| New Times of Minima of Some Eclipsing Binary Stars
Not Available
| 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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