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Hα Observations of the Algol-Type Binary RZ Cassiopeiae
Time-resolved Hα spectra of the Algol-type binary RZ Cas areobtained in the primary minimum. The observed spectral feature at themid-primary minimum does not coincide with that of the secondarycomponent. The observed equivalent widths are found to be larger thanthe modeled one, and the distribution of the differential equivalentwidths of the Hα line is found to be asymmetric relative to themid-primary eclipse. These features indicate that the temporalappearance of a ``flat bottom'' around the mid-primary minimum is causedby the superposition of the light variations due to eclipse and thosedue to the pulsation of the primary component, and also suggest thepresence of circumstellar matter in the system.
| 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 .
| The connection between the pulsational and orbital periods for eclipsing binary systems
Considering a sample of 20 eclipsing binary systems with δ Scutitype primaries, we discovered that there is a possible relation amongthe pulsation periods of the primaries and the orbital periods of thesystems. According to this empirical relation, the longer the orbitalperiod of a binary, the longer the pulsation period of its pulsatingprimary. Among the sample, the masses of the secondaries and theseparations between the components are known for eight systems for whicha logPpuls versus logF (the gravitational pull exerted pergram of the matter on the surface of the primaries by the secondaries)diagram also verifies such an interrelation between the periods. So, asthe gravitational force applied by the secondary component onto thepulsating primary increases, its pulsation period decreases. Thedetailed physics underlying this empirical relation between the periodsneeds further confirmation, especially theoretically. However, one mustalso consider the fact that the present sample does not contain asufficiently large sample of longer period (P > 5 d) binaries.
| Photoelectric Minima of Some Eclipsing Binary Stars
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| New Times of Minima of Eclipsing Binary Systems and of Maximum of SXPHE Type Stars
We present 64 photoelectric minima observations of 31 eclipsingbinaries. We also report three new times of maxima of three SXPHE typepulsating stars.
| 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
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| Bericht uber die Veranderlichen-Beobachtungswoche an der VdS-Sternwarte in Kirchheim.
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| Beobachtungssergebnisse Bundesdeutsche Arbeitsgemeinschaft fuer Veraenderliche Sterne e.V.
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| Observed Orbital Eccentricities
For 391 spectroscopic and visual binaries with known orbital elementsand having B0-F0 IV or V primaries, we collected the derivedeccentricities. As has been found by others, those binaries with periodsof a few days have been circularized. However, those with periods up toabout 1000 or more days show reduced eccentricities that asymptoticallyapproach a mean value of 0.5 for the longest periods. For those binarieswith periods greater than 1000 days their distribution of eccentricitiesis flat from 0 to nearly 1, indicating that in the formation of binariesthere is no preferential eccentricity. The binaries with intermediateperiods (10-100 days) lack highly eccentric orbits.
| δ Sct-type pulsations in eclipsing binary systems: AB Cas
This paper presents simultaneous Strömgren uvby observationscarried out during the years 1998 and 1999 on the Algol-type eclipsingbinary system AB Cas, where the primary component is a δ Sct-typepulsator. These observations include complete binary uvby light curveswhich have been analysed using the Wilson-Devinney code. The new resultsare compared with those from the literature. The residuals from thecomputed binary light curves were then analysed for their pulsationalcontent. A single frequency was found to be sufficient to describe theout-of-eclipse pulsational behaviour. Nevertheless, some indications ofthe existence of secondary frequencies are also found. The main periodwas found to be constant during the last twenty years, making use of theclassical O-C method, but an increase in its amplitude is detectedduring the year 1998 as compared with other epochs. Concerning thenature of the pulsations, methods based on the phase shifts andamplitude ratios between different filters were used for out-of-eclipsedata and the Spatial Filtration method for observations during theprimary eclipses. All methods lead to the same result: the dominantpulsation is radial, confirming previous results from earlier works. Infact, neither significant amplitude variations nor phase shifts,relative to the pulsational out-of-eclipse behaviour, are found when theprimary component is hidden during primary eclipse. An iterative processwas also carried out to improve both the binary and pulsation solutions,but the final results remained essentially the same.
| The pre-main-sequence star HD34282: a very short-period δ Scuti-type pulsator
HD34282 has been found to pulsate during a systematic search forshort-term photometric variability in Herbig Ae/Be stars with the goalof determining the position and size of the pre-main-sequenceinstability strip. Simultaneous Strömgren photometry is used in thefrequency analysis, yielding two frequencies with values ofν1= 79.5 and ν2= 71.3 cycle d-1.The light curve with the largest amplitude is that of the u band. Thisbehaviour, which is not common for δ Scuti stars, is explained aspulsation in a high radial order in stars near the blue edge of theinstability strip. The main period, with a value of 18.12 min,represents the shortest period observed so far for a δ Scuti-typepulsator. A seismic modelling, including instability predictions androtation effects, has been attempted. It is found that bothmain-sequence and pre-main-sequence models predict modes in the range of56 to 82 cycle d-1 (between 648 and 949 μHz),corresponding to oscillations of radial order n from 6 to 8. The highestof the observed frequencies only becomes unstable for models of lowmetallicity, in agreement with results from spectroscopic measurements.
| δ Sct-type pulsations in eclipsing binary systems: RZ Cas
We present the results of a three-continent multisite photometriccampaign carried out on the Algol-type eclipsing binary system RZ Cas,in which the primary component has recently been discovered to be aδ Sct-type pulsator. The present observations include, for thefirst time, complete simultaneous Strömgren uvby light curvestogether with a few Crawford Hβ data collected around the orbitalphase of the first quadrature. The new observations confirm thepulsational behaviour of the primary component. A detailed photometricanalysis, based on these observations, is presented for both binarityand pulsation. The results indicate a semidetached system where thesecondary fills its Roche lobe. The appearance of the light curvesreveals the presence of the mass stream from the secondary component anda hotspot where this stream impacts on the surface of the primary star.There are also some indications of chromospheric activity in thesecondary. On the other hand, the pulsational behaviour out-of-primaryeclipse can be well described with only one frequency at 64.1935cd-1 similar to the main peak found by Ohshima et al. Theexistence of multiperiodicity is not confirmed in our data. Concerningthe mode identification, our results indicate non-radial pulsation in ahigh radial order (n= 6), with l= 2, |m|= 1, 2 as the most suitable.However, additional effects must be taken into account in thepredictions. Moreover, the pulsation amplitude in the u band is largerthan in b and v, which is unusual among the δ Sct-type variables.This can be explained as due to pulsation in a high n value and close tothe blue edge of the δ Sct region. On the other hand, the earlydata of Ohshima et al. have also been analysed and similar results arefound concerning the frequency content and pulsational amplitude.Finally, a revision of all the photometric out-of-primary-eclipse datasets available in the literature is made together with some additionalunpublished data leading to interesting findings relative to changestaking place in the pulsation amplitudes and frequencies from season toseason. Furthermore, multiperiodicity is probably present in someepochs.
| The BAA Observers' Workshops: Observing eclipsing variables: a beginners' guide
The General Catalogue of Variable Stars (GCVS)1 lists many differentclasses of variable star. Some of these are well known and contain manymembers; others are more obscure and contain only a few examples.However, it is also possible to split variable stars into just two basiccategories: the intrinsic variables ? stars like Mira variables, Cepheidvariables, novae and supernovae ? in which the stars themselves arevarying in brightness, and the extrinsic variables, in which theindividual stars themselves do not actually vary, and prominent amongthese are the eclipsing variables.
| Discovery of short-periodic pulsating components in Algol-type eclipsing binary systems EF Her and CT Her
We report a detection of short-periodic pulsating components in theAlgol-type eclipsing binary systems EF Her and CT Her
| RZ Cassiopeiae im Spiegel der astronomischen Photometrie !
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| Tidal Effects in Binaries of Various Periods
We found in the published literature the rotational velocities for 162B0-B9.5, 152 A0-A5, and 86 A6-F0 stars, all of luminosity classes V orIV, that are in spectroscopic or visual binaries with known orbitalelements. The data show that stars in binaries with periods of less thanabout 4 days have synchronized rotational and orbital motions. Stars inbinaries with periods of more than about 500 days have the samerotational velocities as single stars. However, the primaries inbinaries with periods of between 4 and 500 days have substantiallysmaller rotational velocities than single stars, implying that they havelost one-third to two-thirds of their angular momentum, presumablybecause of tidal interactions. The angular momentum losses increase withdecreasing binary separations or periods and increase with increasingage or decreasing mass.
| 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.
| Frequency spectrum of the rapidly-oscillating mass-accreting component of the Algol-type system AS Eri
The first multisite photometric campaign devoted to the rapidlyoscillating mass-accreting (primary) component of the Algol-typeeclipsing binary system AS Eri has confirmed the presence of rapidpulsations with frequency 59.03116 d-1, and revealed thesecond and third oscillation modes with frequencies 62.5631d-1 and 61.6743 d-1, respectively. These modes arerelated to the 5-6 overtone oscillations and are among the shortestperiods excited in non-magnetic MS A-F stars. The nearly equator-onvisibility of eclipsing binaries help to narrow the range of possiblemode identifications for the detectable modes as radial or(l,m)=(1,±1), (l,m)=(2,±2) and (l,m)=(2,±0). Wechecked the high-order pulsation-to-orbital synchronization (POS) usingthe trial mode identification and the Doppler effect correction forfrequencies of non-radial pulsation. We found that (l,m,n)=(1,1,5) or(2,2,5) and (l,m,n)=(2,-2,6) identifications for f1 andf2 modes respectively satisfied the high-order POS. Thesemode identifications are in agreement with the range of modes visible indisk integrated light of an equator-on visible pulsating component.The wavelength distribution of pulsation amplitudes in AS Eri is largestin the Strömgren u filter and decreases toward longer wavelengths.We place AS Eri and other known mass-accreting pulsating components ofAlgols on HR-diagram. They are located inside the instability strip onthe Main Sequence. We also discuss the peculiar evolutionary status ofprimary components in Algols and stress that they are not normal δScuti stars, but form a separate group of pulsators. Finally, we discussproximity and eclipse effects, and have simulated the effect of primaryminimum data gaps that may produce the 1/Porb alias sidelobesin DFT analysis of eclipsing binary data. Aliases from gaps in primaryminimum observations seem to be the principal limitation on spectralwindow functions in asteroseismic studies of eclipsing binaries.
| 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
| The eclipsing binary star RZ Cas. I. First spectroscopic detection of rapid pulsations in an Algol system
In a first report on the results of a multi-site campaign in 2001 ofphotometric and spectroscopic observations of the active semi-detachedAlgol-type system RZ Cas, we concentrate on the radial velocity (RV)variations. Using weak absorption lines we obtain an improved orbitalsolution for both components. In the orbital RV curve we observe astrong, asymmetric rotation effect. For the first time we detect rapidspectroscopic multi-mode pulsations in an Algol system. Whereas thephotometrically observed oscillations were dominated by monoperiodicpulsations at frequency 64.19 c d-1 until the year 2000, wefind in 2001 a multiperiodic behaviour with two dominant frequencies off1=56.600 c d-1 and f2=64.189 cd-1.Both modes show amplitude variations over the orbital phase with a aminimum at orbital phases φ= 0.6-0.8 and a maximum just after theprimary minimum (f2) and at φ ≈ 0.25 (f1).The different shape of amplitude modulation of the f1 andf2 modes points to different (l,m) mode structures. Themodulation itself can be explained by assuming a variable extinction dueto gas streams and an inhomogeneous accretion annulus that weakens thelight from different regions of the primary depending on its orbitalposition. This assumption is well supported by the gas densitydistribution obtained in preliminary hydrodynamic simulations.We found strong variations and cycle-to-cycle variable shapes of theorbital RV-curves of Balmer lines that have maximum magnitude in theHα line indicating a strong variability of mass-transfer rates anda non-stationary circumbinary envelope.The research is based on spectroscopic observations made with the 2-mtelescope at the Thüringer Landessternwarte Tautenburg, Germany.Table 3 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/413/293
| VLA and MERLIN observations of RZ Cassiopeiae
We present radio interferometric observations of the Algol-type binarysystem RZ Cassiopeiae made with the VLA and MERLIN arrays at 6 cm overan incomplete orbital cycle of the system (1.195 d). We detected RZ Caswith both instruments. The images were unresolved in both cases, withangular extents comparable to the synthesized beams. The peak fluxdensity in the VLA image was 1.14 mJy beam-1 and in theMERLIN image it was 0.93 mJy beam-1. The derived brightnesstemperatures are 4.02 × 108 and 4.35 ×108 K and the effective electron energies are 0.347 and 0.346MeV for the MERLIN and VLA data respectively. The radio light curveshows an interesting modulation centred close to the primary eclipsewhich seems to correlate with ASCA SIS observations of the system. Theresults can be interpreted as an emitting region on the outer hemisphereof the cool component aligned along the centroid axis of the binarysystem.
| 162-nd List of Minima Timings of Eclipsing Binaries by BBSAG Observers
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| New Times of Minima of Eclipsing Binary Systems
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| The First Eclipsing Binary Observations at the Ulupinar Astrophysics Observatory
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| Zur qualitat der visuellen Beobachtung kurzperiodisch Veranderlicher.
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| Beobachtungsegebnisse Bundesdeutsche Arbeitsgemainschaft fur Veranderliche Sterne e.V.
Not Available
| VLA Radio Positions of Stars: 1978-1995
VLA astrometric positions of the radio emission from 52 stars arereported, from observations obtained between 1978 and 1995. Thepositions of these stars have been obtained and reduced in a uniformmanner. Based on our measurements, the offset of the optical (Hipparcos)frame from the radio reference frame is in agreement with the Hipparcosextragalactic link results, within their mean errors. Comparison of theVLA measurements with the Hipparcos optical positions confirms earlierestimates of the accuracy of these positions as 30 mas. Long-termmeasurements of UX Ari have improved its proper motion.
| The first CCD photometric study of the open cluster NGC 2126
We present the first CCD photometric observations of the northern opencluster NGC 2126. Data were taken on eight nights in February andDecember 2002 with a total time span of ~ 57 hours. Almost 1000individual V-band frames were examined to find short-period variablestars. We discovered six new variable stars, of which one is a promisingcandidate for an eclipsing binary with a pulsating component. Two starswere classified as delta Scuti stars and one as Algol-type eclipsingbinary. Two stars are slow variables with ambiguous classification. Fromabsolute V(RI)C photometry we have estimated the maincharacteristics of the cluster: m-M=11fm0 +/-0fm5 , E(V-I)=0fm4 +/-0fm1, E(V-R)=0fm08 +/-0fm06 (E(B-V)=0fm2 +/-0fm15 ) and d=1.3+/-0.6 kpc.Cluster membership is suggested for three variable stars from theirpositions on the colour-magnitude diagram.
| Merged catalogue of reflection nebulae
Several catalogues of reflection nebulae are merged to create a uniformcatalogue of 913 objects. It contains revised coordinates,cross-identifications of nebulae and stars, as well as identificationswith IRAS point sources.The catalogue is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/399/141
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Observation and Astrometry data
| Constellation: | Cassiopeia |
| Right ascension: | 02h48m55.50s |
| Declination: | +69°38'03.0" |
| Apparent magnitude: | 6.18 |
| Distance: | 62.539 parsecs |
| Proper motion RA: | 2.8 |
| Proper motion Dec: | 36.4 |
| B-T magnitude: | 6.437 |
| V-T magnitude: | 6.283 |
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INHABITED SKY
