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Photoelectric Minima of Some Eclipsing Binary Stars
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| A period study and light-curve synthesis for the Algol-type semidetached binary XXCephei
We obtained CCD photometric observations of the Algol-type semidetachedbinary XXCephei (XXCep) during 15 nights from 2002 September 17 to 2003February 2, and also on 2005 January 21. Except for those data taken onthe last night of the concentrated observing season, the 3881measurements were obtained over an interval of only 106 nights. Fromthese data, four new times of minimum light were calculated. The (O- C)diagram formed from all available timings, and thus the orbital periodof the system, can be partly represented as a beat effect between twocyclical variations with different periods (yr, yr) and amplitudes(K1=0.015d, K2=0.103d), respectively. Bothphysical and non-physical interpretations of these cycles wereinvestigated. The long-term sinusoidal variation is too long formagnetic cycling in solar-type single and close binary stars. Inaddition, we have studied the effect of a possible secular periodvariation. By analysing the residuals from our Wilson-Devinney (WD)binary model, we found small light variations with a period of 5.99dwith amplitudes growing toward longer wavelengths. We think that theseoscillations may be produced by instabilities at the systemicL1 point (also occupied by the point of the cool star) andthat these instabilities are, in turn, caused by non-uniform andsporadic convection. There is also a short-period oscillation of about45min in the WD light residuals that is attributed to accretion on tothe mass-gaining primary component from a feeble gas stream originatingon the cool donor star.
| A catalogue of close binaries located in the δ Scuti region of the Cepheid instability strip
A catalogue of close eclipsing binary systems (detached andsemidetached) with at least one of the components located in the δScuti region of the Cepheid instability strip is presented. Thepositions of the stars in the instability strip are determined by theiraccurate temperatures and luminosities. Observationally detectedbinaries (20 semidetached, four detached and one unclassified) withoscillating components were included in the catalogue as a separatetable. The primaries of the oscillating Algols tend to be located nearthe blue edge of the instability strip. Using reliable luminosities andtemperatures determined by recent photometric and spectroscopic studies,we have found that at least one or two components of 71 detached and 90semidetached systems are located in the δ Scuti region of theCepheid instability strip. In addition, 36 detached or semidetachedsystems discovered by the Hipparcos satellite were also given as aseparate list. One of their components is seen in the δ Scutiregion, according to their spectral type or B - V colours. They arepotential candidate binaries with the δ Scuti-type pulsatingcomponents which need further photometric and spectroscopic studies inbetter precision. This catalogue covers information and literaturereferences for 25 known and 197 candidate binaries with pulsatingcomponents.
| 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.
| 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.
| An Algol type binary with a δ Scuti component: RZ Cassiopeiae revisited
We present new BV photometry and spectroscopic observations of RZCassiopeiae. The light and radial velocity curves were formed by the newobservations which have been analyzed simultaneously by using theWilson-Dewinney code. The non-synchronous rotational velocityv1sin i = 76 ± 6 km s-1, deduced for theprimary component from the new spectroscopic observations, was alsoincorporated in the analysis. A time-series analysis of the residuallight curves revealed the multi-periodic pulsations of the primarycomponent of RZ Cas. The main peak in the frequency spectrum wasobserved at about 64.197 c d-1 in both B and V bands. Thepulsational constant was calculated to be 0.0116 days. This valuecorresponds to high overtones (n˜6) of non-radial modeoscillations. We find significant changes in the pulsational amplitudeof the primary component from year to year. The peak-to-peak pulsationalamplitude of the main frequency displays a decrease from 0.013 m in 2000to 0.002 m in 2001 and thereafter we have found an increase again in theamplitude to 0.01 m in the year 2002. We propose the mass transfer fromthe cool secondary to the pulsating primary as a possible explanationfor such remarkable changes in the pulsational behavior of the primarycomponent.
| Development of a 1-m Robotic Telescope System
Korea Astronomy & Space Science Institute (KASI) has installed a 1-mrobotic telescope at Mt. Lemmon, AZ, in collaboration with a company,Astronomical Consultants & Equipment, Inc (ACE). The telescopesystem is totally designed to make fully robotic observations, and canbe operated in both interactive and unattended robotic modes. Thetelescope is newly designed and manufactured regarding both mechanicaland optical parts. The optical system is designed to collect 80% of theincident light within 0.''5 with an f/7.5 Ritchey-Chretien design. Thetelescope mount is an equatorial fork with a friction drive system, andit allows fully programmable tracking speeds with a typical range of15'' s-1 and an accuracy of ±5''hr-1. Themount system includes an integral pointing model to correct formechanical errors and misalignments, and an auto-guide unit is alsoavailable. To gather environmental information a weather station and anall sky camera are installed at the site. In this paper we introduce thesystem design and the performance of the mechanical and optical qualityof the telescope system based on the results of test observations usingsome variable stars.
| 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/.
| 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
| 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 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.
| Search for A-F Spectral type pulsating components in Algol-type eclipsing binary systems
We present the results of a systematic search for pulsating componentsin Algol-type eclipsing binary systems. A total number of 14 eclipsingbinaries with A-F spectral type primary components were observed for 22nights. We confirmed small-amplitude oscillating features of a recentlydetected pulsator TW Dra, which has a pulsating period of 0.053 day anda semi-amplitude of about 5 mmag in B-passband. We discovered newpulsating components in two eclipsing binaries of RX Hya and AB Per. Theprimary component of RX Hya is pulsating with a dominant period of 0.052day and a semi-amplitude of about 7 mmag. AB Per has also a pulsatingcomponent with a period of 0.196 day and a semi-amplitude of about 10mmag in B-passband. We suggest that these two new pulsators are membersof the newly introduced group of mass-accreting pulsating stars insemi-detached Algol-type eclipsing binary systems.Table 4 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/405/231
| Period Changes in Four Algol-Type Binaries: SX Dra, AV Del, CU Peg and DK Peg
Orbital period changes of four neglected short-period semidetachedAlgols, SX Dra, AV Del, CU Peg and DK Peg, are presented based on theanalysis of their O-C observations. It is found that the three systems,AV Del, CU Peg and DK Peg, show rapid period increase at rates of dP/dt= +3.15 × 10-6, +2.00 × 10-6 and +4.88× 10-7 days/year respectively. For the other system, SXDra, a possible periodic variation in the orbital period is discoveredto superimpose on a very rapid period increase (dP/dt = +1.09 ×10-5 days/year). The period increases of the four Algols canbe explained by a mass transfer from the secondary to the more massiveprimary, which is in agreement with the semi-detached configurations ofthese systems. However, since the period increases are rather rapid, themass transfer should be on a dynamical time scale. The cyclic periodchange in SX Dra suggests that there may exist a third body in thissystem.
| Detection of a Pulsating Component in the Eclipsing Binary RX Hya
We report detection of a pulsating component in the Algol type eclipsingbinary RX Hya
| 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.
| 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
| Long-time behavior of orbital periods of some Algol-type eclipsing binaries
Orbital period variations of six semi-detached binaries, UW Cyg, RX Hya,AK Ser, AC Tau, UW Vir and VV Vul, are presented based on the analysisof their O-C observations. For AK Ser and VV Vul, their orbital periodsmay show secular increase at rates of dP/dt=+7.94 10-7 and+3.43 10-6 days/year. For UW Cyg, its orbital period isrevised, and the O-C curve shows a cyclic variation with a period of49.2 years and an amplitude of 0fd 0383. For the other three systems, RXHya, AC Tau and UW Vir, the changes in their orbital periods appear morecomplex but their O-C curves can be represented by periodic variations(with periods of 54.3, 29.8 and 45.9 years) superimposed on upwardparabolic segments. The components of upward curving parabolicvariations in RX Hya, AC Tau and UW Vir indicate secular period increasewith rates of dP/dt=+1.04 10-6, +7.11 10-7 and+1.73 10-6 days/year respectively. The secular periodincrease in the five systems, RX Hya, AK Ser, AC Tau, UW Vir and VV Vul,can be explained by mass transfer from the less to the massivecomponents, which is consistent with their semi-detached configurations.The periodic changes of the orbital periods in UW Cyg, RX Hya, AC Tau,UW Vir may be caused by the light-time effects due to the existence ofthe third bodies. Tables 2 to 7 are only available in electronic form athttp://www.edpsciences.org
| Mining in the HIPPARCOS raw data
The Hipparcos solutions flagged as unreliable after the completion ofthe standard data processing have been systematically revisited in thelight of additional information, primarily related to theirmultiplicity. In many cases improved solutions have been obtained,yielding at the same time an Hipparcos based separation and positionangle and a better astrometric solution for the system. The principlesapplied in this reprocessing are explained and more than a hundred newsolutions with absolute and relative astrometry are presented anddiscussed. Tables 1 to 7 are also available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Radio emission from Algol-type binaries. I. Results of 1992-1993 VLA survey
In this paper we report on a 5 GHz survey of 26 Algol-type binaries. Sixsystems were detected. We combine the new results with previouslypublished data to derive some radio characteristics of Algols and tocompare them with those of other active binaries. The radio detectionrate of 30 %, a factor that is somewhat smaller compared to the case ofRSCVn-type, does not seem to be due to a reduced coronal activity. Infact, Algols share many similarities with the radio behavior of RS CVnsand the 5 GHz luminosity functions of both kind of systems look quitesimilar. Among the different possibilities, the high radio variabilityand distances, which, on average, are larger than those of RS CVns, seemto be the most reasonable explanation for the apparently reducedactivity at radio wavelengths.
| My experiences as an astronomer and a survey of binary star research carried out at CASA
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| Interaction of Eclipsing Binaries with their Environment
The interaction of eclipsing binary star systems with the mass around(in the form of star, planet, envelope or disk) affects the orbitalperiod of these systems. Thus, the long-term orbital period changes ofeclipsing binaries which can be deduced by using the observed times ofeclipse minima provide a good tool in understanding the interaction ofeclipsing binaries with their environment. In the present contributionmany examples of the orbital period changes of different eclipsingbinaries are presented and interpreted in terms of the interaction withtheir environment.
| On the nature of the AM phenomenon or on a stabilization and the tidal mixing in binaries. I. Orbital periods and rotation.
The paper casts a questioning eye on the unique role of the diffusiveparticle transport mechanism in explaining the Am phenomenon and arguesthat the so-called tidal effects might be of great importance incontrolling diffusion processes. A short period cutoff at =~1.2d as wellas a 180-800d gap were found in the orbital period distribution (OPD) ofAm binaries. The existence of the former can be ascribed to the state ofthe primaries with the almost-filled Roche lobes. The latter couldresult from the combined effects of the diffusion, tidal mixing andstabilization processes. Because the tidal mixing might surpassdiffusion in the binaries with the orbital periods P_orb_ less thanseveral hundred days and might thus sustain the He convection zone,which would otherwise disappear, no Am stars should lie below thisboundary. The fact that they are nevertheless seen there implies theexistence of some stabilization mechanism (as, e.g., that recentlyproposed by Tassoul & Tassoul 1992) for the binaries with orbitalperiods less than 180d. Further evidence is given to the fact that theOPD for the Am and the normal binaries with an A4-F1 primary arecomplementary to each other, from which it stems that Am stars are closeto the main sequence. There are, however, indications that they haveslightly larger radii (2.1-3 Rsun_) than expected for theirspectral type. The generally accepted rotational velocity cutoff at=~100km/s is shown to be of little value when applied on Am binaries ashere it is not a single quantity but, in fact, a function of P_orb_whose shape is strikingly similar to that of the curves of constantmetallicity as ascertained from observations. This also leads to thewell known overlap in rotational velocities of the normal and Am starsfor 402.5d.We have exploited this empirical cutoff function to calibrate thecorresponding turbulent diffusion coefficient associated with tidalmixing, having found out that the computed form of the lines of constantturbulence fits qualitatively the empirical shape of the curves ofconstant metallicity. As for larger orbital periods(20d55km/s found by Burkhart(1979) would then be nothing but a manifestation of insufficientlypopulated corresponding area of larger P_orb_.
| 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.
| Radio continuum emission from stars: a catalogue update.
An updated version of my catalogue of radio stars is presented. Somestatistics and availability are discussed.
| Gravitational radiation and spiralling time of close binary systems. IV
Binary systems with their primary and secondary component masses lessthan 2 solar masses have been investigated to evaluate the rate ofemission of gravitational energy (PB) and spiralling time (tau exp 0)for them. In all, 22 binary systems have been considered. It is foundthat in spite of the same mass range, these systems form two distinctgroups. New relations have been given between PB and tau exp 0 for eachgroup. For a few eccentric orbit systems the rate of decay of orbitalperiods due to the loss of energy from the system via giavitationalradiation emission has also been given and compared with a short-periodbinary pulsar.
| The visual surface brightness method and the radii of dwarf Cepheids
In order to determine the radii of dwarf Cepheids by applying the visualsurface brightness method, the empirical relationship between F(v) and(b - y) was derived. Seventeen stars of spectral type A to F, where bothangular diameters and uvby beta photometric data are available, wereselected from the literature. A theoretical F(v), (b-y) relation wasderived by using the Kurucz model atmospheres. It was found that thetheoretical relation is strongly dependent upon metallicity and surfacegravity. To demonstrate that the visual surface brightness method is aneffective way to determine the radii of dwarf Cepheids, both theoreticaland empirical relations were applied to seven dwarf Cepheids. The mostreliable result was obtained for AD CMi where the quality of the radialvelocity data is superior.
| Photometric analysis of the eclipsing binary RX Hydrae
Complete photoelectric U, B, and V light curves were obtained for thesingle-lined eclipsing binary, RX Hydrae, in 1983-1987. The resultssuggest that the system is a semidetached Algol-type binary in which thesecondary is filling its roche lobe. Also, results are given from aperiod variation study for RX Hydrae.
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