Programmsterne: beobachtungen erwuenscht.
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Polarimetric measures of selected variable stars
Aims. The purpose of this paper is to summarize and interpretunpublished optical polarimetry for numerous program stars that wereobserved over the past decades at the Flower and Cook Observatory (FCO),University of Pennsylvania. We also make the individual calibratedmeasures available for long-term comparisons with new data. Methods: Weemploy three techniques to search for intrinsic variability within eachdataset. First, when the observations for a given star and filter arenumerous enough and when a period has been determined previously viaphotometry or spectroscopy, the polarimetric measures are plotted versusphase. If a statistically significant pattern appears, we attribute itto intrinsic variability. Second, we compare means of the FCO data tomeans from other workers. If they are statistically different, weconclude that the object exhibits long-term intrinsic variability.Third, we calculate the standard deviation for each program star andfilter and compare it to the standard deviation estimated fromcomparable polarimetric standards. If the standard deviation of theprogram star is at least three times the value estimated from thepolarimetric standards, the former is considered intrinsically variable.All of these statements are strengthened when variability appears inmultiple filters. Results: We confirm the existence of anelectron-scattering cloud at L1 in the β Per system, andfind that LY Aur and HR 8281 possess scattering envelopes. Intrinsicpolarization was detected for Nova Cas 1993 as early as day +3. Wedetected polarization variability near the primary eclipse of 32 Cyg.There is marginal evidence for polarization variability of the βCepheid type star γ Peg. The other objects of this class exhibitedno variability. All but one of the β Cepheid objects (ES Vul) fallon a tight linear relationship between linear polarization and E(B-V),in spite of the fact that the stars lay along different lines of sight.This dependence falls slightly below the classical upper limit ofSerkowski, Mathewson, and Ford.The table, which contains the polarization observations of the programstars discussed in this paper, is only available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/489/911
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Programmsterne: Beobachtungen erwuenscht.
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Modelling eclipsing binaries with pulsating components: Phase dependence of observed pulsation amplitudes
We investigate the phase dependence of the light variations due topulsations, as modulated with light variations due to the eclipses. Thestudy is based, both on a simplified model and on the rigorous lightcurve (LC) synthesis software of Wilson and Devinney. We model AB Cas asa prototype, using both of these approaches. The phase dependence of thedifferential light variations for total systems is also discussed .
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New Minimum Times of Eclipsing Binaries
I report 16 visual minimum times of eclipsing binaries.
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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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Aus der Sektion Bedeckungsveranderliche.
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Wer beobachtet mit? UX Monocerotis.
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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.
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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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δ Scuti stars and their related objects
δ Scuti stars are a group of stars located on or a little abovethe main sequence of H-R diagram with spectral type from A3 to F5. Theyare low amplitude single or multi period pulsators with period shorterthan 0.3 d. Within the same area there are several groups of variablesor special stars correlated with them, e.g., Dwarf Cepheids, γ Dorvariables, Blue Stragglers, Am stars, Ap stars, ROAp variables, λBoo variables and δ Del variables. In this paper a general reviewin this field, including the number of new variables discovered after1995, is presented. The most reliable period variation rates for all thehigh amplitude variables and several low amplitude variables are listed.Statistic shows the higher the rotation rate v sin i is, the lower thelight variation amplitude is. Thus within young open clusters highamplitude variables cannot be found. The amplitudes-periods distributionhave 3 peaks with the highest of 1.0 mag in V at 0.17 d in period. Forδ Scuti variables in stellar systems the shorter the averageperiod is, the lower the metallicity and the older the age of thestellar system are.
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Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veraenderliche Sterne e.V.
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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
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delta Scuti and related stars: Analysis of the R00 Catalogue
We present a comprehensive analysis of the properties of the pulsatingdelta Scuti and related variables based mainly on the content of therecently published catalogue by Rodríguez et al.(\cite{retal00a}, hereafter R00). In particular, the primaryobservational properties such as visual amplitude, period and visualmagnitude and the contributions from the Hipparcos, OGLE and MACHOlong-term monitoring projects are examined. The membership of thesevariables in open clusters and multiple systems is also analyzed, withspecial attention given to the delta Scuti pulsators situated ineclipsing binary systems. The location of the delta Scuti variables inthe H-R diagram is discussed on the basis of HIPPARCOS parallaxes anduvbybeta photometry. New borders of the classical instability arepresented. In particular, the properties of the delta Scuti pulsatorswith nonsolar surface abundances (SX Phe, lambda Boo, rho Pup, delta Deland classical Am stars subgroups) are examined. The Hipparcos parallaxesshow that the available photometric uvbybeta absolute magnitudecalibrations by Crawford can be applied correctly to delta Scutivariables rotating faster than v sin i ~ 100 km s{-1} withnormal spectra. It is shown that systematic deviations exist for thephotometrically determined absolute magnitudes, which correlate with vsin i and delta m1. The photometric calibrations are found tofit the lambda Boo stars, but should not be used for the group ofevolved metallic-line A stars. The related gamma Dor variables and thepre-main-sequence delta Scuti variables are also discussed. Finally, thevariables catalogued with periods longer than 0fd 25 are examined on astar-by-star basis in order to assign them to the proper delta Scuti, RRLyrae or gamma Dor class. A search for massive, long-period delta Scutistars similar to the triple-mode variable AC And is also carried out.
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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 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.
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A Photometric and Spectrophotometric Study of MR Cygni
A self-consistent, physically accurate program suite has been used in anaccurate simulation of new spectroscopy and photometry of MR Cygni.Analysis of both the spectroscopic and photometric data used spectrumsynthesis techniques and a synthetic photometry augmentation of a lightsynthesis program package. The theoretical light curves closely fit theobservational data. The same self-consistent parameters from the lightsynthesis solution produced synthetic spectra precisely fitting theobserved spectra at all orbital phases. The IRAF-reduced spectroscopyhas produced an accurate double-lined radial velocity curve. The derivedmass ratio differs greatly from photometric mass ratios in theliterature. New UBV photometry closely replicates existing data andindicates photometric stability of the binary system. A syntheticspectrum fitted to IUE data established the primary component Teff. Thelight curve solution determined a single set of system parameters usedto calculate U, B, and V light curves. We conclude that MR Cygni is amember of the relatively rare class of hot Algol systems defined byPopper. It is likely that mass transfer still is in progress, but thereis no evidence, either from orbital period variation or from a brightspot on the mass gainer, for its existence. The lack of H alpha emissionin any of our spectra, including one at phase 0.063, suggests a smallcurrent rate of mass transfer. The fact that our computationallyself-consistent procedure has successfully represented both thephotometry and the spectroscopy for a binary system whose components areappreciably distorted demonstrates the overall power of the procedure.
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Luminosity and related parameters of δ Scuti stars from HIPPARCOS parallaxes. General properties of luminosity.
The absolute magnitudes of δ Scuti stars derived from parallaxesmeasured by the Hipparcos astrometric satellite are discussed andcompared with the previous estimates based on photometric uvbyβindices. There are significant differences which are related tophotometric effects of metallicity and rotational velocity, but thepossible effect of a close companion on the measured apparent magnitudeshould be also taken into account. The possibility of differentgroupings of δ Scuti stars based on the absolute magnitudes isbriefly discussed. Some high amplitude δ Scuti stars withintermediate or normal metallicity and small and uncertain parallax haveapparently a very low luminosity; this could be a systematic effectrelated to the observational errors.
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Chemical Evolution of Algols
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Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
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UX Monocerotis: New Photometric and Spectroscopic Observations, Solutions, and Anomalies in an Active Mass-Transferring Binary
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995AJ....110.2385O&db_key=AST
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O I lamba 7774 absorption as a tracer of streams and disks in nondegenerate binary stars
We propose a new spectroscopic approach for observing circumstellarmatter in binary stars, based on the neutral oxygen lambda 7774absorption lines. We present oxygen equivalent widths and radialvelocities in 20 nondegenerate eclipsing binaries. We note limitationsand advantages of using this line to trace circumstellar matter inbinary systems, and confirm the presence of streams and rotatingaccretion disks in a number of short- long-period Algol systems. Wediscuss evidence for geometrically thick disks, and describe a smallradial infall superimposed on disk rotation in most long-period systems.We speculate that infall may be related to viscous dissipation in disks.We emphasize the great sensitivity of lambda 7774 in studying thekinematics of circumstellar matter in many nondegenerate binary stars.
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A catalogue of variable stars in the lower instability strip.
Identifications, positions, photometry, spectra, some pulsationalfeatures, other astrophysical parameters and literature for 302pulsating variable stars in the lower instability strip, near the ZAMS,are given. About 185 stars have near homogeneous photometric informationin the Stroemgren's uvby-β photometric system. Thiscatalogue/database covers information published until November 1993.
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Radio continuum emission from stars: a catalogue update.
An updated version of my catalogue of radio stars is presented. Somestatistics and availability are discussed.
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On X-ray interacting binaries with no compact components.
Our present knowledge of the interacting binary β Persei (Algol) onthe basis of published X-ray and EUV observations is summarized and somegeneral comments on future work are made.
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δ Scuti stars: a new revised list
An extensive and up to date list of δ Sct stars is presented. Thiscatalogue is intended to be a comprehensive review of observationalcharacteristics of all the δ Sct stars known until now, includingstars contained in earlier catalogues together with other new discoveredvariables, covering information published until November 1993. Globalinformation in the form of histograms and diagrams are also shown.
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Quantitative spectral types for 19 Algol secondaries
Time-resolved spectra of 19 short-period Algol-type binary star systemsobtained during total eclipse are used to derive the temperaturespectral class of the mass-losing secondary component. The spectralclassifications employed a quantitative comparison of the strengths ofabsorption features in stars of known spectral class with those of theprogram stars. The luminosity spectral class can not be determined fromthese data, so both main-sequence and giant stars were used for thecomparison. Our spectral types are compared with published types andfound to be generally in good agreement, unless the published types arederived from the light curves. The photometrically determined types aresystematically later than our directly determined types. This effect isshown also to exist in catalogs of Algol parameters.
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Wind driven mass transfer in interacting binary systems
Quantitative estimates for conditions governing wind-driven masstransfer in interacting binary systems are presented. It is shown that,for a semidetached system in which the lobe-filling star is a red giant,mass loss from this star by the system as a whole can drive masstransfer. If the mass is lost on a sufficiently short time-scale, thiswind-driven mass transfer can dominate over the traditional-nucleardriven mass transfer. If additional angular momentum is lost because theescaping material is forced to corotate out to some Alfven radius, themass transfer can be driven at an even greater rate. In this case therates of mass transfer and of mass loss can be quantified as functionsof the mass ratio and the Alfven radius. Some numerical models of theexpected evolution are presented and observational predictions areexamined. It is found that the radii of evolved semidetached systems aremore consistent with wind-driven evolution than the traditionalnuclear-driven Riche-lobe overflow.
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A microwave survey of selected Algol systems with the VLA
The results are presented of a limited microwave survey of Algol-typesystems carried out with the VLA. Seven of the fourteen observed systemswere detected. The average radio luminosity at 6 cm L6 turnedout to be 1.58 x 10 exp 16 erg/s/Hz, and thus comparable to the medianradio luminosity for the larger sample of RS CVn reported by Morris andMutel (1988). The high values of the brightness temperature, obtained byassuming a characteristic dimension for the emission region, suggest anonthermal origin for the radio emission. The observations areconsistent with gyrosynchrotron emission from mildly relativisticelectrons interacting with the magnetic field of the active component.This makes Algol-type systems comparable to the RS CVn class of binaryradio sources.
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Pulsating Variable Stars in Binary Systems
Lists of variable stars in binary systems are presented.
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INHABITED SKY
