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New Minimum Times of Eclipsing Binaries
I report 16 visual minimum times of eclipsing binaries.
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| Evolution of interacting binaries with a B type primary at birth
We revisited the analytical expression for the mass ratio distributionfor non-evolved binaries with a B type primary. Selection effectsgoverning the observations were taken into account in order to comparetheory with observations. Theory was optimized so as to fit best withthe observed q-distribution of SB1s and SB2s. The accuracy of thistheoretical mass ratio distribution function is severely hindered by theuncertainties on the observations. We present a library of evolutionarycomputations for binaries with a B type primary at birth. Some liberalcomputations including loss of mass and angular momentum during binaryevolution are added to an extensive grid of conservative calculations.Our computations are compared statistically to the observeddistributions of orbital periods and mass ratios of Algols. ConservativeRoche Lobe Over Flow (RLOF) reproduces the observed distribution oforbital periods but fails to explain the observed mass ratios in therange q in [0.4-1]. In order to obtain a better fit the binaries have tolose a significant amount of matter, without losing much angularmomentum.
| 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.
| Minima Kurt Locher 2004-2005
Minima observed 2004..2005 by Kurt Locher visually, not accepted by IBVSas part of BBSAG Bulletin.
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| Beobachtungssergebnisse Bundesdeutsche Arbeitsgemeinschaft fuer Veraenderliche Sterne e.V.
Not Available
| Times of Minima for Some Eclipsing Binaries
Times of minima for a number of some eclipsing binaries are presented.
| 163. List of Minima Timings of Eclipsing Binaries by BBSAG Observers
Not Available
| Doppler tomography of Algols
The technique of Doppler tomography has been influential in the study ofmass transfer in Algol-type interacting binaries. The Algols contain ahot blue dwarf star with a magnetically-active late-type companion. Inthe close Algols, the gas stream flows directly into the photosphere ofthe blue mass-gaining star because it does not have enough room to avoidimpact with that star. Doppler tomograms of the Algols have beenproduced from over 2500 time-resolved spectra at wavelengthscorresponding to Hα, Hβ, He I (6678 Å), Si II (6371Å) and Si IV (1394 Å). These tomograms display images ofaccretion structures that include a gas stream, accretion annulus,accretion disk, stream-star impact region, and occasionally a source ofchromospheric emission associated with the cool, mass-losing companion.Some Algol systems alternate between stream-like and disk-like states,and provide direct evidence of active mass transfer within the Algols.This work produced the very first images of the gas stream for theentire class of interacting binaries, and demonstrated that the Algolsare far more active than formerly believed, with variability on timescales of weeks to months.
| Catalogue of Algol type binary stars
A catalogue of (411) Algol-type (semi-detached) binary stars ispresented in the form of five separate tables of information. Thecatalogue has developed from an earlier version by including more recentinformation and an improved layout. A sixth table lists (1872) candidateAlgols, about which fewer details are known at present. Some issuesrelating to the classification and interpretation of Algol-like binariesare also discussed.Catalogue is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/417/263
| Archive of Photometric Plates Obtained at Cluj Astronomical Observatory
The archive of photometric plates obtained at the AstronomicalObservatory of Cluj in the period 1952-1974 is presented. The plateinventory is made within the framework of the Wide-Field Plate Databaseproject. The plates were taken in the regions around 110 variable stars(eclipsing variables and RR Lyrae-type stars), as well as in somecomparison stars regions.
| 162-nd List of Minima Timings of Eclipsing Binaries by BBSAG Observers
Not Available
| 149 Bedeckungssterne der BAV-Programme. Eine Analyse der Beobachtungstatigkeit seit den Angangen.
Not Available
| Das Brunner Punktesystem.
Not Available
| Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veraenderliche Sterne e.V.
Not Available
| The Origin of Cyclic Period Changes in Close Binaries: The Case of the Algol Binary WW Cygni
Year- to decade-long cyclic orbital period changes have been observed inseveral classes of close binary systems, including Algol, W UrsaeMajoris, and RS Canum Venaticorum systems and the cataclysmic variables.The origin of these changes is unknown, but mass loss, apsidal motion,magnetic activity, and the presence of a third body have all beenproposed. In this paper, we use new CCD observations and thecentury-long historical record of the times of primary eclipse for WWCygni to explore the cause of these period changes. WW Cyg is an Algolbinary whose orbital period undergoes a 56 yr cyclic variation with anamplitude of ~0.02 days. We consider and reject the hypotheses of masstransfer, mass loss, apsidal motion, and the gravitational influence ofan unseen companion as the cause for these changes. A model proposed byApplegate, which invokes changes in the gravitational quadrupole momentof the convective and rotating secondary star, is the most likelyexplanation of this star's orbital period changes. This finding is basedon an examination of WW Cyg's residual O-C curve and an analysis of theperiod changes seen in 66 other Algols. Variations in the gravitationalquadrupole moment are also considered to be the most likely explanationfor the cyclic period changes observed in several different types ofbinary systems.
| Der Algolstern XZ And - Nichts zum Einschlafen.
Not Available
| 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.
| A Search for High-Velocity Be Stars
We present an analysis of the kinematics of Be stars based uponHipparcos proper motions and published radial velocities. We findapproximately 23 of the 344 stars in our sample have peculiar spacemotions greater than 40 km s-1 and up to 102 kms-1. We argue that these high-velocity stars are the resultof either a supernova that disrupted a binary or ejection by closeencounters of binaries in young clusters. Be stars spun up by binarymass transfer will appear as high-velocity objects if there wassignificant mass loss during the supernova explosion of the initiallymore massive star, but the generally moderate peculiar velocities of BeX-ray binaries indicate that the progenitors lose most of their massprior to the supernova (in accordance with model predictions). Binaryformation models for Be stars predict that most systems bypass thesupernova stage (and do not receive runaway velocities) to createultimately Be+white dwarf binaries. The fraction of Be stars spun up bybinary mass transfer remains unknown, since the post-mass transfercompanions are difficult to detect.
| Short-Period Light Variation of an Eclipsing Binary System: RZ Cassiopeiae
The eclipsing binary system RZ Cas is known to exhibit variation in itslight curves at the primary minimum, usually showing apartial-eclipse-type curve but sometimes indicating a flat minimum,which is evidence for a total eclipse. We observed RZ Cas not onlyduring the primary eclipse, but also during the out-of-eclipse phase,and we have found a short-period light variation with a frequency of62.20 cycles day-1 (period of 23.15 minutes), whose maximumamplitude is 0.02 mag. This short-period variation can modulate theshape of the light curve at the primary minimum effectively. Thebrightness-color relationship of the short-period variation suggests aδ Scuti type oscillation.
| Survey of Hα Mass Transfer Structures in Classical Algol-Type Binaries
Five years of Hα survey data for 37 ``classical'' Algol-typebinaries are presented. All these systems have primaries with a spectraltype of A or B, have a period of less than 5 days, and are visible inthe Northern Hemisphere. Data were collected with the 1.02 m reflectorat the US Naval Observatory, Flagstaff Station. The survey consists ofover 460 system spectra. Each system was observed at least once duringthe 5 years, with many systems observed several times over severalepochs. Difference profiles are calculated for most spectra by modelingand subtracting the spectrum of the photospheres of the stellarcomponents. We examined each spectrum for the presence of mass transfer,stream-star and stream-disk interaction, a disk or circumstellar bulge,and chromospheric emission. We present information on the prevalence ofmass transfer activity, disk presence, and system states associated withparticular mass transfer structures. We show that no currently publishedstudy, including this one, has enough data for a rigorous statisticalidentification of system states.
| Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| CCD Minima of Selected Eclipsing Binaries in 1999
Not Available
| A Multiwavelength Study of Spectral Variations in the CX Draconis Binary
An extensive collection of spectroscopic observations of the interactingbinary CX Dra spanning a 23 year interval have been analyzed. This studyincludes a refinement of the orbital solution of CX Dra; equivalentwidth measurements that show short-, medium-, and long-term behavior ofthe difference profiles; a calculation of the Balmer decrement; velocitymaps based on the velocity curves of the Hα and He I differenceemission peaks; trailed spectrograms of the Hα, Hβ, He I, andSi II lines; and Doppler tomograms at these four wavelengths. The mainconclusions are: 1. The circumstellar environment in the system changesin cycles of hundreds of days. The length of the cycles is variable.These cycles may be part of a ``super'' 4000 day cycle. 2. Theequivalent widths of the difference Hα and He I λ6678 linesare modulated with the orbital period of 6.696 days. The correspondingphase diagrams indicate a great deal of scatter, but the modulation isquite conspicuous when long data strings are used. The pattern of thephase diagram suggests a permanent presence of the emission in Hα,He I λ6678, and Si II λ6371 lines. 3. The radialvelocities of the Hα emission peak follow an S-wave. The resultingvelocity map shows that the source of the single-peaked emission liesclose to the L1 point, roughly between the primary and L1 point. 4.Doppler tomograms constructed for Hα observed and differenceprofiles show that the emission comes from a region of low velocity, agas stream, and an accretion disk. The Hβ emission arises from aregion that is cospatial with the Hα source. The Doppler tomogramsfor He I λ6678 and Si II λ6371 lines suggest that emissionin this gas also originates from a locus of a disk around the primarystar. 5. The model based on the equivalent widths of the differenceprofiles, the trailed spectrograms, and Doppler tomograms of theHα, He I λ6678, Si II λ6371, and Hβ linessuggests that the main source of the Hα emission is about halfwaybetween the stars at a distance of 0.49a from the primary star, and thatthe He I and Si II emission sources arise from an accretion diskcentered on the primary star.
| Is asynchronism in semidetached binary systems real?
We analyze statistical relationships between the parameters ofAlgol-type binaries with asynchronous rotation of the primary componentsand provide observational evidence for denser, more extended gaseousenvelopes in the eclipsing systems of this group. We conclude thatasynchronism of the primary components in such systems is not real. Thelines that are used to determine the rotational velocities of thesecomponents originate mostly in the part of the atmosphere which acquiresan additional angular momentum during the interaction with the gasstream and produces a transient accretion disk near the equatorialplane.
| Morphologies of Hα Accretion Regions in Algol Binaries
We have investigated a group of 18 Algol-type binaries to determine thegeneral morphologies and physical properties of the accretion regions inthese systems. The systems studied were V505 Sgr, RZ Cas, AI Dra, TVCas, TW Cas, delta Lib, RW Tau, TW Dra, beta Per, TX UMa, U Sge, S Equ,U CrB, RS Vul, SW Cyg, CX Dra, TT Hya, and AU Mon, in order ofincreasing orbital period P=1.18-11.11 days. In addition, the RSCVn-type binary HR 1099 (V711 Tau) was observed to illustrate theappearance of chromospheric Hα emission. Nearly 2200 time-resolvedHα spectra were collected from 1992 March to 1994 December withthe McMath-Pierce Solar Telescope at NSO and mostly with theCoudé Feed Telescope at KPNO. The spectra were obtained at phasesaround the entire orbit of each binary and were closely spaced to permitthe detection of transitions in the profiles. Moreover, the spectra wereobtained typically within three orbital cycles to reduce the influenceof secular variations. Difference profiles were calculated bysubtracting a composite theoretical photospheric spectrum from theobserved spectrum. The analysis of the Hα difference profilesdemonstrates that the accretion structures in Algol binaries have fourbasic morphological types: (1) double-peaked emission systems in whichthe accretion structure is a transient or classical accretion disk; (2)single-peaked emission systems in which the accreted gas was found alongthe trajectory of the gas stream and also between the two stars in anaccretion annulus; (3) alternating single- and double-peaked emissionsystems, which can change between a single-peaked and a double-peakedtype within an orbital cycle; and (4) weak spectrum systems in whichthere was little evidence of any accretion structure since thedifference spectra are weak at all phases. The first two types are thedominant morphologies. The first type can be interpreted physically as adisklike distribution, while the second is a gas stream-likedistribution. The most common type in short-period Algols with 2.7days6 days)were found to have slightly variable but permanent accretion disks atall epochs (i.e., CX Dra, TT Hya, and AU Mon), similar to those found incataclysmic variables. SW Cyg (P=4.57 days) was found to be anintermediate case between the shorter period systems with P<4.5 daysand the longer period group with P>6 days. Two systems, U Sge and UCrB, displayed alternating single- and double-peaked emission atdifferent epochs (Type 3), and changes from one type to another weredetected within a 12 hour time interval. Observations at multiple epochssuggest that four members of the single-peaked emission group, namely RWTau, TX UMa, S Equ, and RS Vul, may actually belong to the alternatinggroup. So, the complete group of alternating systems covers periods of2.7 days
| Hα Spectroscopy of RW Monocerotis
Five years of sparse full-orbit Hα spectroscopy are presented forthe short-period Algol RW Monocerotis. A spectroscopic mass ratio isderived that confirms the published photometric mass ratio. Of the twopublished rotation rates of the primary star, 66 and 260 kms-1, the slower best fits our observations. Hα emissionwas not seen during any of five eclipses, indicating that the secondaryis notstrongly chromospherically active. At every epoch an emissionfeature between the two stars was found, confirming that there iscontinuous mass transfer. However, an accompanying accretion disk wasseen in only two of six observing runs, using out-of-eclipsespectroscopy. Comparing with models, we show how a single out-of-eclipseHα observation can provide information on the mass transferpresence at that epoch. Finally, we see redshifted absorption justbefore and after primary eclipse, consistent with the location andvelocity of a mass transfer stream. However, the Hα absorptionequivalent width (with respect to the out-of-eclipse continuum) fallsproportionally with the primary's visibility between first and secondcontact. This indicates that the stream is projected against the entireface of the primary, a much larger area than predicted by theory.
| Variations of the orbital periods in semi-detached binary stars with radiative outer layers
A detailed analysis of the period changes of sixteen semi-detachedbinaries which contain only stars with radiative outer layers(ET-systems) has been performed and their respective O-C diagrams arebrought and discussed. It was found that the course of the periodvariations is monotonic and in some systems the period is even constant.This detailed analysis of extensive sets of timings covering severaldecades brings a strong support to an earlier finding of te[Hall(1989)]{hal89} and develops it further. We show that all systems withthe orbital periods shorter than nine days display constant period orits increase, with the exception of an uncertain case of V 337 Aql. Thecourse of the period variations in TT Aur appears more complex but thecyclic term can be plausibly explained by the third body. A search forgeneral relations between the parameters of the systems and the periodchanges was undertaken. The mass ratio q appears to play a role in theperiod variations. Clear changes in systems with orbital periods shorterthan 9 days were detected only for q>0.4 while constant periods arecommon in systems with q<0.4 in this period range. The sense of thesecular changes in most systems is in accordance with the dominantconservative mass transfer in evolved binary and corresponds to the slowphase. The role of the evolutionary scenarios (case A versus B) and theinfluence of changes of the rotational angular momenta of the componentsare discussed.
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