All-Sky Automated Survey eclipsing binaries with observed high period change rates
We present 31 bright eclipsing contact and semidetached binaries thatshowed high period change rates (HPCRs) in a 5-yr interval inobservations by the All-Sky Automated Survey. The time-scales of thesechanges range from only 50 up to 400 kyr. The orbital periods of 10binaries are increasing and of 21 are decreasing, and even a largerexcess is seen in contact binaries, where the numbers are 5 and 17,respectively. Period change has previously been noticed for only two ofthese binaries; our observations confirmed a secular period drift for SVCen and period oscillations for VY Cet. The spectroscopic quadruplesystem V1084 Sco shows both period change and brightness modulation.According to our results, the incidence of asymmetry in the brightnessat maximum light in the HPCR domain may be different from the incidencein the general population. All investigated binaries were selected froma sample of 1711 (1135 contact and 576 semidetached) that fulfilled allcriteria of data quality. We also introduce a `branch' test to check ifluminosity changes on part of the binary's photosphere have led to aspurious or poorly characterized period change detection.
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Variation in the orbital period of W UMa-type contact systems
The secular variation in the orbital period Porb is studiedas a function of the mass ratio q of the components in a sample of 73contact systems of class W UMa constructed from a survey of current(1991–2003) published photometric and spectroscopic data. Almostall the W UMa-systems (>93% of this sample) are found to have avariation in their orbital periods Porb which alternates insign independently of their division into A-and Wsubclasses. Astatistical study of this sample in terms of the observedcharacteristics dPorb/dt and q showed that on the average thenumbers of increases (35 systems) and decreases (33 systems) in theperiods are the same, which indicates the existence of flows directedalternately from one component to the other and illustrates the cyclicalcharacter of the thermal oscillations. An analysis of the behavior ofdPorb/dt as a function of the mass interval of the primarycomponent yields a more accurate value for the mass ratio, q ≈ 0.4÷ 0.45 at which contact binaries are separated into A-andW-subclasses. No correlations were observed between the fill-out factorfor the outer contact configuration, the total mass of the contactsystem, and the mass ratio of the components, on one hand, and the signof the secular variation in the period. The physical properties andevolutionary features of these systems are discussed.
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Contact Binaries with Additional Components. I. The Extant Data
We have attempted to establish observational evidence for the presenceof distant companions that may have acquired and/or absorbed angularmomentum during the evolution of multiple systems, thus facilitating orenabling the formation of contact binaries. In this preliminaryinvestigation we use several techniques (some of themdistance-independent) and mostly disregard the detection biases ofindividual techniques in an attempt to establish a lower limit to thefrequency of triple systems. While the whole sample of 151 contactbinary stars brighter than Vmax=10 mag gives a firm lowerlimit of 42%+/-5%, the corresponding number for the much better observednorthern-sky subsample is 59%+/-8%. These estimates indicate that mostcontact binary stars exist in multiple systems.
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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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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
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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/.
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Catalogue of the field contact binary stars
A catalogue of 361 galactic contact binaries is presented. Listedcontact binaries are divided into five groups according to the type andquality of the available observations and parameters. For all systemsthe ephemeris for the primary minimum, minimum and maximum visualbrightness and equatorial coordinates are given. If available,photometric elements, (m1+m2)sin3i,spectral type, parallax and magnitude of the O'Connell effect are alsogiven. Photometric data for several systems are augmented by newobservations. The quality of the available data is assessed and systemsrequiring modern light-curve solutions are selected. Selectedstatistical properties of the collected data are discussed.
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Stars with the Largest Hipparcos Photometric Amplitudes
A list of the 2027 stars that have the largest photometric amplitudes inHipparcos Photometry shows that most variable stars are all Miras. Thepercentage of variable types change as a function of amplitude. Thiscompilation should also be of value to photometrists looking forrelatively unstudied, but large amplitude stars.
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A note on thermally decoupled W Ursae Majoris systems
The thermal decoupling degree of short-period contact or near-contactsystems is studied. Statistics of well-observed W UMa systems includingnew beta-light-curve objects was made for thermal-decoupling degree,spectral type, and orbital period. W UMa systems of type A and W arefound to be well characterized by these parameters. W-type objects showa good (linear) correlation in the spectral type vs. thermal-decouplingparameter diagram. This extends to the lower border of the diagram forA-type systems, otherwise scattered in an area of large thermaldecoupling. These empirical facts are analyzed in terms of contact ornoncontact configurations.
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Studies of Period Variation in Close Binary Systems
Abstract image available at:http://adsabs.harvard.edu/abs/1987AJ.....94..792L
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UBV photometric analysis of V758 Centauri
Classical R-M and synthetic W-D analysis of V758 Centauri are presented.Two solutions (semi-detached and contact) were found from differentialcorrections approach. The semi-detached model is physically acceptablesince the system is thermally decoupled. The solution for this case andthe photometric data are consistent with a B9 primary and A9 secondarycomponents having parameters close to main-sequence values. It issuggested that V758 Centauri is a B-type W UMa system at thebroken-contact phase predicted by the Thermal Relaxation Oscilllationstheory.
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V758 Centauri - UBV photometry
The W UMa system V758 Centauri has been observed photoelectrically inthe UBV system at Bosque Alegre Station, and the comparison and checkstars at Cerro Tololo Observatory. Full light curves were constructedfrom 1043 differential UBV observations. A study of 11 photoelectrictimes of minimum light and of earlier photographic data shows that theperiod remained constant in the last century; V758 Cen shows a totaloccultation at secondary minimum, thus being an A-type W UMa system.Asymmetries are observed at primary minima whereas maxima are ofdifferent heights. Thermal decoupling of the components is suggested bythe depth ratio of the minima; V758 Cen may be at the broken phase (ormarginal contact) of a thermal relaxation oscillation.
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V758 Cen, Light Curve and Study of the Period
Not Available
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Four-colour and H-beta photometry for early type stars in three southern galactic regions
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&AS...41...85L&db_key=AST
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58th Name-List of Variable Stars
Not Available
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Results of the Bamberg Southern Hemisphere Sky Patrol [erratum: 1969MNSSA..28...79S]
Not Available
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Light Curve of BV 1101
Not Available
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New Bright Southern BV-Stars
Not Available
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Langfristige Periodenkontrolle fur Bedeckungsveranderliche der Bamberger Liste.
Not Available
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INHABITED SKY
