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Orbital Solutions and Absolute Elements of the Eclipsing Binary EE Aquarii
EE Aqr is a 7.9 mag Algol variable with a 12 hr orbital period. TheWilson-Devinney program is used to simultaneously solve 11 previouslypublished light curves together with two existing radial velocitycurves. The resulting masses are M 1 = 2.24 ± 0.13 Msun and M 2 = 0.72 ± 0.04 M sun,and the radii are R 1 = 1.76 ± 0.03 R sunand R 2 = 1.10 ± 0.02 R sun. The system hasthe lower-mass component completely filling its Roche lobe. Its distancefrom Hipparcos observations is 112 ± 10 pc. An improved ephemerisis derived, and no deviations in the period over time were seen. Lightand velocity curve parameters, orbital elements, and absolute dimensionsare presented, plus a comparison is made with previous solutions.
| A spectroscopic survey of the youngest field stars in the solar neighbourhood. I. The optically bright sample
Aims: We present the first results of an ambitious ground-basedobservation programme conducted on 1-4 m class telescopes. Our sampleconsists of 1097 active and presumably young stars, all of them beingoptical (Tycho Catalogue) counterparts of ROSAT All-Sky Survey X-raysources in the northern hemisphere. In this paper, we concentrate on theoptically brightest (V_T?slant 9.5 m) candidates (704 objects). Weacquired high-resolution optical spectroscopy in the H? and/orlithium spectral regions for 426 of such stars without relevant data inthe literature. We describe the star sample and the observations and westart to discuss the physical properties of the investigated stars. Methods: We used a cross-correlation technique and other toolsdeveloped by us to derive accurate radial and rotational velocities andto perform an automatic spectral classification for both single starsand double-lined systems. The spectral subtraction technique was used toderive chromospheric activity levels and lithium abundances. Weestimated the fraction of young single stars and multiple systems instellar soft X-ray surveys and the contamination by more evolvedsystems, like RS CVn binaries. We classified stars on the basis of theirlithium abundance and give a glimpse of their sky distribution. Results: The sample appears to be a mixture of quite youngPleiades-like and Hyades-like stars plus an older lithium-poorpopulation probably born within the last 1-2 Gyr. Seven stars with alithium abundance compatible with the age of IC 2602 (about 30 Myr) oreven younger were detected as well, although two appear to belithium-rich giants.The discovery of a large number of highly ormoderately lithium-rich giants is another outcome of the present survey. Conclusions: The contamination of soft X-ray surveys by oldsystems in which the activity level is enhanced by tidal synchronisationis not negligible, especially for K-type stars. Five stars with lithiumcontent close to the primordial abundance are probably associated withalready known moving groups in the solar neighbourhood. Some of them aregood post-T Tauri candidates according to their positions in the HRdiagram.Based on observations collected at the Observatoire de Haute Provence(France) and the Catania Astrophysical Observatory (Italy). Data for the426 stars 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/504/829
| A catalogue of chromospherically active binary stars (third edition)
The catalogue of chromospherically active binaries (CABs) has beenrevised and updated. With 203 new identifications, the number of CABstars is increased to 409. The catalogue is available in electronicformat where each system has a number of lines (suborders) with a uniqueorder number. The columns contain data of limited numbers of selectedcross references, comments to explain peculiarities and the position ofthe binarity in case it belongs to a multiple system, classicalidentifications (RS Canum Venaticorum, BY Draconis), brightness andcolours, photometric and spectroscopic data, a description of emissionfeatures (CaII H and K, Hα, ultraviolet, infrared),X-ray luminosity, radio flux, physical quantities and orbitalinformation, where each basic entry is referenced so users can go to theoriginal sources.
| The rotation-activity correlation among G and K giants in binary systems
Aims.The present study aims (i) to test the existence of a correlationbetween magnetic activity and rotation among G and K giants in binarysystems and (ii) to test whether parameters other than rotation play arole in determining the X-ray emission level of intermediate-massgiants. Methods: The method consists in testing the existence ofcorrelations between measured stellar parameters including the X-raysurface flux, rotation period, Rossby number and surface gravity of asample of G and K giants with masses included between 1.5 M_ȯ and3.8 M_ȯ. Results: I found evidence that the X-ray surface fluxFX of intermediate-mass G and K giants is correlated withtheir rotation period P as previously observed on single G giants.Confidence in the degree of correlation is not higher when the Rossbynumber is used in place of the rotation period, but it significantlyimproves when stellar gravity g is taken into account. The empiricalrelation given by log (F_X) = -0.73 × log (P) + 0.64 × log(g/gȯ)+ 7.9 differs from the power-law dependence withan index of about -2 between X-ray to bolometric luminosity ratio andthe rotation period that is observed for main-sequence stars. The X-raysurface flux of single G giants and of intermediate-mass G and K giantsin close binary systems, such as RS CVn systems, also depends on thestellar gravity. This dependence could result from the effect of gravityon the electron density and emission measure of the X-ray emittingplasmas, as well as on the characteristic sizes of coronal magneticloops. The measured X-ray surface-flux dependence on gravity is,however, not as steep as the one predicted by simple models ofhydrostatic loops that assume a fixed ratio between the coronal energylosses by thermal conduction and by radiation. Conclusions: .I concludethat (i) a relation exists between the rotation and X-ray activity levelin giants, (ii) that this relation is not directly dependent on thepresence of a companion and applies to all intermediate-mass giants witheither G or K spectral type, and (iii) that gravity is an importantstellar parameter in determining the X-ray surface flux ofintermediate-mass giants.
| Dynamical evolution of active detached binaries on the logJo-logM diagram and contact binary formation
Orbital angular momentum (OAM, Jo), systemic mass (M) andorbital period (P) distributions of chromospherically active binaries(CAB) and W Ursae Majoris (W UMa) systems were investigated. Thediagrams of and logJo-logM were formed from 119 CAB and 102 WUMa stars. The logJo-logM diagram is found to be mostmeaningful in demonstrating dynamical evolution of binary star orbits. Aslightly curved borderline (contact border) separating the detached andthe contact systems was discovered on the logJo-logM diagram.Since the orbital size (a) and period (P) of binaries are determined bytheir current Jo, M and mass ratio, q, the rates of OAM loss(dlogJo/dt) and mass loss (dlogM/dt) are primary parametersto determine the direction and the speed of the dynamical evolution. Adetached system becomes a contact system if its own dynamical evolutionenables it to pass the contact border on the logJo-logMdiagram. The evolution of q for a mass-losing detached system is unknownunless the mass-loss rate for each component is known. Assuming q isconstant in the first approximation and using the mean decreasing ratesof Jo and M from the kinematical ages of CAB stars, it hasbeen predicted that 11, 23 and 39 per cent of current CAB stars wouldtransform to W UMa systems if their nuclear evolution permits them tolive 2, 4 and 6 Gyr, respectively.
| HD 71636, A Newly Discovered Eclipsing Binary
Our differential BV photometric observations, acquired with an automatedtelescope at Fairborn Observatory, show that HD 71636 is an eclipsingbinary. From follow-up red-wavelength spectroscopic observations weclassify the primary and secondary as an F2 dwarf and an F5 dwarf,respectively. The system has a period of 5.01329 days and a circularorbit. We used the Wilson-Devinney program to simultaneously solve ourBV light curves and radial velocities and determined a number offundamental properties of the system. Comparison with evolutionarytracks indicates that both stars are well ensconced on the mainsequence. The age of the system is about 1.2 billion years.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Speckle Measurements and Differential Photometry of Visual Binaries with the 6 Meter Telescope of the Special Astrophysical Observatory
Results of speckle measurements and differential photometry carried outwith the 6 m telescope of the Special Astrophysical Observatory (Russia)at the end of 2004 are presented. One new (COU 1569) and four improvedorbits (ADS 440AC, ADS 1729, ADS 5726, and COU 1897), as well as theirdynamical mass estimates, are reported.
| Tertiary companions to close spectroscopic binaries
We have surveyed a sample of 165 solar-type spectroscopic binaries (SB)with periods from 1 to 30 days for higher-order multiplicity. Asubsample of 62 targets were observed with the NACO adaptive opticssystem and 13 new physical tertiary companions were detected. Anadditional 12 new wide companions (5 still tentative) were found usingthe 2MASS all-sky survey. The binaries belong to 161 stellar systems; ofthese 64 are triple, 11 quadruple and 7 quintuple. After correction forincompleteness, the fraction of SBs with additional companions is foundto be 63% ± 5%. We find that this fraction is a strong functionof the SB period P, reaching 96% for P<3d and dropping to34% for P>12^d. Period distributions of SBs with and withouttertiaries are significantly different, but their mass ratiodistributions are identical. The statistical data on the multiplicity ofclose SBs presented in this paper indicates that the periods and massratios of SBs were established very early, but the periods of SB systemswith triples were further shortened by angular momentum exchange withcompanions.
| New Minimum Times of Eclipsing Binaries
I report 16 visual minimum times of eclipsing binaries.
| Mass loss and orbital period decrease in detached chromospherically active binaries
The secular evolution of the orbital angular momentum (OAM), thesystemic mass (M=M1+M2) and the orbital period of114 chromospherically active binaries (CABs) were investigated afterdetermining the kinematical ages of the subsamples which were setaccording to OAM bins. OAMs, systemic masses and orbital periods wereshown to be decreasing by the kinematical ages. The first-orderdecreasing rates of OAM, systemic mass and orbital period have beendetermined as per systemic OAM, per systemic mass and per orbitalperiod, respectively, from the kinematical ages. The ratio of d logJ/dlogM= 2.68, which were derived from the kinematics of the presentsample, implies that there must be a mechanism which amplifies theangular momentum loss (AML) times in comparison to isotropic AML ofhypothetical isotropic wind from the components. It has been shown thatsimple isotropic mass loss from the surface of a component or bothcomponents would increase the orbital period.
| 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.
| Optical Photometry and Spectroscopy of the Suspected ``Cool Algol'' AV Delphini: Determination of the Physical Properties
We present new spectroscopic and BVRI photometric observations of thedouble-lined eclipsing binary AV Del (period=3.85 days) conducted oversix observing seasons. A detailed radial velocity and light-curveanalysis of the optical data shows the system to be most likelysemidetached, with the less massive and cooler star filling its Rochelobe. The system is probably a member of the rare class of ``coolAlgol'' systems, which are distinguished from the ``classical'' Algolsystems in that the mass-gaining component is also a late-type starrather than a B- or A-type star. By combining the spectroscopic andphotometric analyses, we derive accurate absolute masses for thecomponents of M1=1.453+/-0.028Msolar andM2=0.705+/-0.014Msolar and radii ofR1=2.632+/-0.030Rsolar andR2=4.233+/-0.060Rsolar, as well as effectivetemperatures of 6000+/-200 and 4275+/-150 K for the primary andsecondary, respectively. There are no obvious signs of activity(spottedness) in the optical light curve of the binary.
| The Eclipsing Binary System AR Monocerotis
New differential UBV photoelectric photometry and echelle spectroscopyfor the eclipsing binary AR Mon are presented. A total of 46 radialvelocities for each component are obtained using the TODCOR procedure.We solve the new and previously published multicolor light curvessimultaneously with the new radial velocities using the latest versionof the Wilson-Devinney program. We confirm that AR Mon is a semidetachedbinary consisting of two evolved giant stars and is a member of the rareclass of ``cool Algols.'' The size of the primary, more massivecomponent is about 1/3 that of its limiting lobe, and the secondary staris a lobe filler. We present two solutions, one without third light, theother including amounts of third light of 8% in V, 6% in B, and 5% in U.We determine magnitudes and colors for AR Mon's two components, as wellas for the third star. If real, the latter is estimated to be a dwarfforeground star. The mass and radius of the primary(2.480+/-0.014Msolar, 8.002+/-0.089Rsolar) placethe star very close to the evolutionary track of a 2.5Msolarsingle star of solar chemical composition, indicating that the star mayhave adjusted its structure to mass gained from its companion.Synchronous rotation rates for both stars are in excellent agreementwith vsini values determined from line profiles.
| Mg II chromospheric radiative loss rates in cool active and quiet stars
The Mg II k emission line is a good indicator of the level ofchromospheric activity in late-type stars. We investigate the dependenceof this activity indicator on fundamental stellar parameters. To thispurpose we use IUE observations of the Mg II k line in 225 late-typestars of luminosity classes I-V, with different levels of chromosphericactivity. We first re-analyse the relation between Mg II k lineluminosity and stellar absolute magnitude, performing linear fits to thepoints. The ratio of Mg II surface flux to total surface flux is foundto be independent of stellar luminosity for evolved stars and toincrease with decreasing luminosity for dwarfs. We also analyse the MgII k line surface flux-metallicity connection. The Mg II k emissionlevel turns out to be not dependent on metallicity. Finally, the Mg II kline surface flux-temperature relation is investigated by treatingseparately, for the first time, a large sample of very active and normalstars. The stellar surface fluxes in the k line of normal stars arefound to be strongly dependent on the temperature and slightly dependenton the gravity, thus confirming the validity of recently proposedmodels. In contrast, data relative to RS CVn binaries and BY Dra stars,which show very strong chromospheric activity, are not justified in theframework of a description based only on acoustic waves and uniformlydistributed magnetic flux tubes so that they require more detailedmodels.
| 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.
| Updated Elements for Southern Eclipsing Binaries
Analysis of ASAS-3 data for 442 southern eclipsing binaries yielded 131stars with incorrect periods listed in the GCVS catalog
| 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/.
| Kinematics of chromospherically active binaries and evidence of an orbital period decrease in binary evolution
The kinematics of 237 chromospherically active binaries (CABs) werestudied. The sample is heterogeneous with different orbits andphysically different components from F to M spectral-type main-sequencestars to G and K giants and supergiants. The computed U, V, W spacevelocities indicate that the sample is also heterogeneous in velocityspace. That is, both kinematically younger and older systems exist amongthe non-evolved main sequence and the evolved binaries containing giantsand subgiants. The kinematically young (0.95 Gyr) subsample (N= 95),which is formed according to the kinematical criteria of moving groups,was compared with the rest (N= 142) of the sample (3.86 Gyr) toinvestigate any observational clues of binary evolution. Comparing theorbital period histograms between the younger and older subsamples,evidence was found supporting the finding of Demircan that the CABs losemass (and angular momentum) and evolve towards shorter orbital periods.The evidence of mass loss is noticeable on the histograms of the totalmass (Mh+Mc), which is compared between theyounger (only N= 53 systems available) and older subsamples (only N= 66systems available). The orbital period decrease during binary evolutionis found to be clearly indicated by the kinematical ages of 6.69, 5.19and 3.02 Gyr which were found in the subsamples according to the periodranges of logP<= 0.8, 0.8 < logP<= 1.7 and 1.7 < logP<=3, respectively, among the binaries in the older subsample.
| 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
| A study of the Mg II 2796.34 Å emission line in late-type normal and RS CVn stars
We carry out an analysis of the Mg II 2796.34 Å emission line inRS CVn stars and make a comparison with the normal stars studied in aprevious paper (Paper I). The sample of RS CVn stars consists of 34objects with known HIPPARCOS parallaxes and observed at high resolutionwith IUE. We confirm that RS CVn stars tend to possess wider Mg II linesthan normal stars having the same absolute visual magnitude. However, wecould not find any correlation between the logarithmic line width logWdeg and the absolute visual magnitude MV (theWilson-Bappu relationship) for these active stars, contrary to the caseof normal stars addressed in Paper I. On the contrary, we find that astrong correlation exists in the (MV, log LMg II)plane (LMg II is the absolute flux in the line). In thisplane, normal and RS CVn stars are distributed along two nearly parallelstraight lines with RS CVn stars being systematically brighter by ~1dex. Such a diagram provides an interesting tool to discriminate activefrom normal stars. We finally analyse the distribution of RS CVn and ofnormal stars in the (log LMg II, log Wdeg) plane,and find a strong linear correlation for normal stars, which can be usedfor distance determinations.
| Optical Photometry and X-Ray Monitoring of the ``Cool Algol'' BD +05°706: Determination of the Physical Properties
We present new photometric observations in the BVRI bands of thedouble-lined eclipsing binary BD +05°706 conducted over threeobserving seasons, as well as new X-ray observations obtained with ROSATcovering a full orbital cycle (P=18.9 days). A detailed light-curveanalysis of the optical data shows the system to be semidetached,confirming indications from an earlier analysis by Torres et al.(published in 1998), with the less massive and cooler star filling itsRoche lobe. The system is a member of the rare class of cool Algolsystems, which are different from the ``classical'' Algol systems inthat the mass-gaining component is also a late-type star rather than aB- or A-type star. By combining the new photometry with a reanalysis ofthe spectroscopic observations reported by Torres et al., we deriveaccurate absolute masses for the components ofM1=2.633+/-0.028 Msolar andM2=0.5412+/-0.0093 Msolar, radii ofR1=7.55+/-0.20 Rsolar andR2=11.02+/-0.21 Rsolar, as well as effectivetemperatures of 5000+/-100 and 4640+/-150 K, for the primary andsecondary, respectively. There are obvious signs of activity(spottedness) in the optical light curve of the binary. Our X-ray lightcurve clearly shows the primary eclipse but not the secondary eclipse,suggesting that the primary star is the dominant source of the activityin the system. The depth and duration of the eclipse allow us to infersome of the properties of the X-ray-emitting region around that star.
| Reprocessing the Hipparcos Intermediate Astrometric Data of spectroscopic binaries. II. Systems with a giant component
By reanalyzing the Hipparcos Intermediate Astrometric Data of a largesample of spectroscopic binaries containing a giant, we obtain a sampleof 29 systems fulfilling a carefully derived set of constraints andhence for which we can derive an accurate orbital solution. Of these,one is a double-lined spectroscopic binary and six were not listed inthe DMSA/O section of the catalogue. Using our solutions, we derive themasses of the components in these systems and statistically analyzethem. We also briefly discuss each system individually.Based on observations from the Hipparcos astrometric satellite operatedby the European Space Agency (ESA 1997) and on data collected with theSimbad database.
| The Evolution of Cool Algols
We apply a model of dynamo-driven mass loss, magnetic braking, and tidalfriction to the evolution of stars with cool convective envelopes; inparticular, we apply it to binary stars where the combination ofmagnetic braking and tidal friction can cause angular momentum loss fromthe orbit. For the present we consider the simplification that only onecomponent of a binary is subject to these nonconservative effects, butwe emphasize the need in some circumstances to permit such effects inboth components.The model is applied to examples of (1) the Sun, (2) BYDra binaries, (3) Am binaries, (4) RS CVn binaries, (5) Algols, and (6)post-Algols. A number of problems regarding some of these systems appearto find a natural explanation in our model. There are indications fromother systems that some coefficients in our model may vary by a factorof 2 or so from system to system; this may be a result of the chaoticnature of dynamo activity.
| Determination of the Ages of Close Binary Stars on the Main Sequence from Evolutionary Model Stars of Claret and Gimenez
A grid of isochrones, covering a wide range of stellar ages from thezero-age main sequence to 10 billion years, is calculated in the presentwork on the basis of the model stars of Claret and Gimenez withallowance for convective overshoot and mass loss by the components. Theages of 88 eclipsing variables on the main sequence from Andersen'scatalog and 100 chromospherically active stars from Strassmeier'scatalog are calculated with a description of the method of optimuminterpolation. Comparisons with age determinations by other authors aregiven and good agreement is established.
| Einige interessante Bedeckungsveraenderliche.
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| The comparative accuracy of photographic observations of radio stars observed at the Engelhardt Astronomical Observatory
At the Engelhardt Astronomical Observatory (EAO), we observedphotographic positions of 113 Galactic Radio Sources (GRS) in the systemPPM catalogue (Rizvanov & Dautov 1998). Analysis of their accuracyis made by comparison with the Hipparcos catalogue (Perryman et al.1997) and astrometric catalogue of radio stars in the radio window fromthe article of Walter et al. (1991). Table 2 is only available inelectronic form at the 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/375/670
| 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
| 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.
| S 10947 Aquilae == RX J2009.8+1557: a probable RS CVn star which sometimes stops its eclipses
We report the discovery of a new variable star, called S 10947 Aql, asthe likely optical counterpart of RX J2009.8+1557. The opticalvariability pattern as well as the detected X-ray emission suggest thatit is a chromospherically active binary of the RS Canum Venaticorum(equiv RS CVn) type. We discovered an occasional disappearance of theeclipsing minima as well as large variations in the eclipse amplitude.We discuss possible causes of this peculiarity. The complete Table 1 isavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
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Osservazione e dati astrometrici
| Costellazione: | Unicorno |
| Ascensione retta: | 07h20m48.45s |
| Declinazione: | -05°15'35.8" |
| Magnitudine apparente: | 8.777 |
| Distanza: | 276.243 parsec |
| Moto proprio RA: | 5.7 |
| Moto proprio Dec: | -5.9 |
| B-T magnitude: | 10.153 |
| V-T magnitude: | 8.891 |
Cataloghi e designazioni:
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