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 Times of minima from observations made from March 2010 throughSeptember 2010, along with a few unpublished times of minima from olderdata, are presented.
|
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.
|
BAV-Results of Observations - Photoelectric minima of selected eclipsing binaries and maxima of pulsating stars.
Not Available
|
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.
|
DM Delphini: A Progenitor of a Contact Binary with a Compact Tertiary Companion
The orbital period of the short-period eclipsing binary DM Del wasanalyzed by using two newly determined eclipse times together with theothers compiled from the literature. It has been discovered that theperiod shows a long-time continuous decrease at a rate of dP/dt =?2.27 × 10-7d yr-1, while it undergoesa cyclic variation with a period of 31.73 years. Meanwhile, photometriclight curves of a close binary in the B and V bands, published byGüdür et al., were analyzed with the 2003 version of the W-Dcode. It was found that the system is a semi-detached binary with alobe-filling primary and a mass ratio of q = 0.55. The long-time perioddecrease can be explained by mass transfer from the primary to thesecondary. This is consistent with the semi-detached configuration. Thegeometrical structure of the binary and the long-term period decreasesuggest that DM Del may be a progenitor of an overcontact binary or justin a broken-contact stage predicted by thermal relaxation oscillations.A cyclic period change reveals the presence of a tertiary unseencompanion that may play an important role in the formation of the closebinary by removing angular momentum from the central system.
|
BAV-Results of Observations - Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
|
Near-Contact Binaries with Mass Transfer: V473 Cassiopeiae and II Persei
Photometric solutions of two short period close binaries, V473 Cas andII Per, are derived with the 2003 version Wilson-Van Hamme code. It isshown that V473 Cas is a semidetached system with the primary componentor the secondary component at its critical Roche Lobe, while II Per is amarginal contact binary system with both components filling theircritical Roche Lobes, but with a large temperature difference betweenthe two components. Both systems belong to near-contact binaries withthe light curves enhanced around the left shoulder of secondary minimum,which can be explained by hot spots on the secondary components due tothe mass transfer via a stream hitting the facing surface of thesecondary components. The orbital period investigations based on allavailable times of light minimum show a secular period existing in thesetwo targets decreasing at the rate of dP/dt = –7.61 ×10–8 days yr–1 for V473 Casand dP/dt = –7.54 ×10–8 days yr–1 for II Per.The decrease of the orbital period can be the result of mass transferfrom the primary component to the secondary one, which is consistentwith the asymmetric light curves of V473 Cas and II Per. Therefore, V473Cas and II Per are other examples displaying evidence of mass transferbetween the two components. We have collected NCBs with secular periodvariation and find that almost all SD1-type NCBs show decreasing periodsand enhancing luminosity on the left shoulder of secondary minimum intheir light curves. So the semidetached configuration with the lobefilling primary is more plausible for V473 Cas. Furthermore, thedetected enhancing amplitude of luminosity for SD2-type NCBs is smallerthan other types of NCBs, which implies that the mass transfer from theprimary component to the secondary one is stronger than the transfer inopposite direction. With the orbital period decrease, V473 Cas and IIPer will evolve into overcontact binaries with true thermal contact.
|
BAV-Results of observations - Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
|
Theoretical improvement of methods for judging the synchronization of self rotations of stars in a spectroscopic binary system.
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
|
New ? Lyrae and Algol Candidates from the Northern Sky Variability Survey
We have classified 409 objects in the Northern Sky Variability Survey(NSVS) as new ? Lyrae or Algol-type eclipsing binaries. Thesecandidates have outside of eclipse magnitudes of ~10-13. Throughautomated Fourier analysis routines and some manual inspection, we listthe period, eclipse depths, coordinates, an estimate of the time ofprimary eclipse, and the 2MASS colors for these candidates. This list ofnew ? Lyrae type candidates greatly increases the number of knownsystems of this type. We have also identified 37 candidate low-mass,main-sequence pairs (M 1,2 < 1 M sun, T <5500 K) in the NSVS database. If confirmed, these systems will greatlyincrease the number of such low-mass systems known as well as helpconstrain atmospheric models for these types of stars.
|
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.
|
Period analysis of three close binary systems: TW And, TT Her and W UMi
Orbital period changes of three close binaries, TW And, TT Her and WUMi, were studied using the Kraków data base of minima ofeclipsing binaries, and new photoelectric observations obtained by theauthors. The interval of the observations spans roughly a century. Themajor orbital period change in TW And is explained by the presence of athird body with P3 = 49.6 yr and a continuous secular periodincrease. A third body, with P3 = 41.0 yr, was also found inthe system TT Her. The (O-C) diagram of W UMi can be interpreted aseither an abrupt orbital period decrease which occurred around the endof 1973 or as a secular orbital period decrease combined with cyclicchange. In this case, the orbital period of the third body is 62.2 yrand the sum of squares of residuals is lower than for a broken-line fit,therefore cyclic variations should be preferred. In all three systems,the third body is a low-mass companion.
|
B.R.N.O. Contributions #34
Not Available
|
TZ Lyrae: an Algol-type Eclipsing Binary with Mass Transfer
We present a detailed investigation of the Algol-type binary TZ Lyrae,based on 55 light minimum timings spanning 90 years. It is found thatthe orbital period shows a long-term increase with a cyclic variationsuperimposed. The rate of the secular increase is dP/dt=+7.18×10^{-8} d yr^{-1}, indicating that a mass transfer from the less massivecomponent to the more massive one at a rate of dm=+2.21×10^{-8}M_? yr^{-1}. The cyclic component, with a period of P_{3}=45.5 yrand an amplitude of A=0.0040°, may be interpreted as either thelight-time effect in the presence of a third body or magnetic activitycycles in the components. Using the latest version Wilson-Devinney code,a revised photometric solution was deduced from B and V observations.The results show that TZ Lyr is an Algol-type eclipsing binary with amass ratio of q=0.297(±0.003). The semidetached configurationwith a lobe-filling secondary suggests a mass transfer from thesecondary to the primary, which is in agreement with the long-termperiod increase of the binary system.
|
Photoelectric Minima of Some Eclipsing Binary Stars
We present 119 minima times of 47 eclipsing binaries.
|
Orbital period variation of the eclipsing binary system TT Herculis
% New photoelectric U BV observations were obtained for the eclipsingbinary TT Her at the Ankara University Observatory(AUO) and three new times of minima were calculated from theseobservations. The (O-C) diagram constructed for all available times ofminima of TT Her exhibits a cyclic character superimposed on a quadraticvariation. The quadratic character yields an orbital period decreasewith a rate of dP/dt=-8.83×10-8 day yr-1which can be attributed to the mass exchange/loss mechanism in thesystem. By assuming the presence of a gravitationally bound third bodyin the system, the analysis of the cyclic nature in the (O-C) diagramrevealed a third body with a mass of 0.21 M\sun orbitingaround the eclipsing pair. The possibility of magnetic activity cycleeffect as a cause for the observed cyclic variation in the (O-C) diagramwas also discussed.
|
BL Andromedae and GW Tauri: close binary stars in a key evolutionary stage
A photoelectric light curve of BL And is presented along with the firstCCD light curve of GW Tau. Both objects are short-period eclipsingbinaries and were observed in 2003 or 2004. Photometric elements werecomputed using the latest version of the Wilson-Van Hamme code. Theresults reveal that BL And is a semidetached system with the primarycomponent filling its Roche lobe and the secondary one almost fillingbut still detached, while GW Tau is a marginal-contact binary systemwith a small degree of contact (f= 10.9 per cent) and a largetemperature difference of about 3100K. All available eclipse times,including new ones, were analysed for each system. It was found that theorbital period of BL And is decreasing at the rate of dP/dt=-2.36× 10-8 (+/-0.09)dyr-1 while that of GW Taumay be decreasing or oscillating. We think period decrease is moreprobable. The derived configuration and secular period decrease for BLAnd combined with the asymmetry of the light curve indicate that thissystem may evolve from the present semidetached phase into a contactstage, with mass transfer from the primary component to the secondaryone through the L1 point, or that it might just undergo thebroken stage predicted by the theory of thermal relaxation oscillations.In contrast, GW Tau is a marginal-contact binary in poor thermal contactand may be at the beginning of the contact phase.
|
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.
|
Automatic classification of eclipsing binaries light curves using neural networks
In this work we present a system for the automatic classification of thelight curves of eclipsing binaries. This system is based on aclassification scheme that aims to separate eclipsing binary systemsaccording to their geometrical configuration in a modified version ofthe traditional classification scheme. The classification is performedby a Bayesian ensemble of neural networks trained with Hipparcos data ofseven different categories including eccentric binary systems and twotypes of pulsating light curve morphologies.
|
Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
|
On the properties of contact binary stars
We have compiled a catalogue of light curve solutions of contact binarystars. It contains the results of 159 light curve solutions. Theproperties of contact binary stars were studied using the cataloguedata. As is well known since Lucy's (\cite{Lucy68a},b) and Mochnacki's(\cite{Mochnacki81}) studies, primary components transfer their ownenergy to the secondary star via the common envelope around the twostars. This transfer was parameterized by a transfer parameter (ratio ofthe observed and intrinsic luminosities of the primary star). We provethat this transfer parameter is a simple function of the mass andluminosity ratios. We introduced a new type of contact binary stars: Hsubtype systems which have a large mass ratio (q>0.72). These systemsshow behaviour in the luminosity ratio- transfer parameter diagram thatis very different from that of other systems and according to ourresults the energy transfer rate is less efficient in them than in othertypes of contact binary stars. We also show that different types ofcontact binaries have well defined locations on the mass ratio -luminosity ratio diagram. Several contact binary systems do not followLucy's relation (L2/L1 =(M2/M1)0.92). No strict mass ratio -luminosity ratio relation of contact binary stars exists.Tables 2 and 3 are available in electronic form athttp://www.edpsciences.org
|
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.
|
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/.
|
CCD Minima for Selected Eclipsing Binaries in 2003
Not Available
|
Short-period near-contact binary systems at the beginning of the overcontact phase
A detailed analysis of orbital period changes of seven near-contactbinary stars (NCBs) (BL And, V473 Cas, XZ CMi, BV Eri, RU Eri, UU Lynand GR Tau) with period less than 1 d has been performed and theirrespective O-C diagrams are formed and discussed. It is found that allsystems analysed show secular period decreasing. For V473 Cas, theanalysis of the period change was performed based on data collected byMoschner, Frank & Bastian. For XZ CMi, its period shows some complexchanges, a possible cyclic oscillation is discovered to superpose on thesecular decrease that can be explained either by the presence of a thirdbody or by magnetic activity cycles of the components. Since thethird-body assumption is consistent with the photometric solution ofRafert, XZ CMi may be a truly triple system. For BV Eri, the perioddecrease is only supported by weak evidence. All the seven systems areshort-period NCBs with AF-type primary components where both componentsare filling or nearly filling the critical Roche lobe. As the perioddecreases, the separation between both components will be reducing andthus these systems will evolve into A-type overcontact binaries. Theperiod decrease may be caused by mass transfer or/and by angularmomentum loss via magnetic braking. Combined with the published data onthe other systems of the same type, a possible statistical connectionbetween orbital period P and its rate of decrease dP/dt is obtained:dP/dt=-5.3 × 10-7×P+ 1.3 × 10-7d yr-1. This correlation indicates that the smaller theorbital period P is, the smaller its rate of change dP/dt will be. Thecorrelation found in this paper indicates that there may be a smoothtransition from A- and F-type NCBs with period decreases to the A- andF-type overcontact binaries that have period increases, and in thatsense one may postulate that the NCBs may be the progenitors of theA-type W UMa systems and will be oscillating around a marginal-contactstate as predicted by thermal relaxation oscillation (TRO) theory.
|
BO Pegasi: A candidate on the breaking stage of the TRO cycle
A detailed period study of the short-period (P=0fd 58) close binarysystem, BO Peg, is presented based on the analysis of its O-C curve. Itis found that the orbital period shows a continuous decrease with a ratedP/dt =-1.26 x10-7 days/year while it undergoes a possiblesmall-amplitude oscillation. If the period oscillation is cyclic, it canbe explained either by the light-time effect via the presence of anunseen third body or by the magnetic activity cycle of the secondarycomponent. The continuous period decrease suggests a secular masstransfer from the more massive to the less massive component, which isin agreement with the near-contact configuration with a lobe-fillingprimary (Yamasaki & Okazaki \cite{Yam-86}). These observations, asseen in RT Scl, FT Lup, TT Her, RS Ind, and V388 Cyg, are consistentwith the Thermal Relaxation Oscillation (TRO) theory in that the primarycomponent is transferring mass to the secondary in the broken-contactphase. To satisfy such a decrease in the orbital period, a conservativemass transfer rate (with no magnetic effect) would be of the order ofdM/dt =-1.53x10-7 Msun/year.
|
INHABITED SKY
