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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.
| Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity
We present rotational and radial velocities for a sample of 761 giantsselected from the Hipparcos Catalogue to lie within 100 pc of the Sun.Our original goal was to examine stellar rotation in field giants usingspectroscopic line broadening to look for evidence of excess rotationthat could be attributed to planets that were engulfed as the parentstars expanded. Thus we were obliged to investigate other sources ofline broadening, including tidal coupling in close binaries andmacroturbulence. For all the binaries in our sample with periods shorterthan 20 days the orbits have been circularized, while about half theorbits with periods in the range 20-100 days still show significanteccentricity. All our primaries in orbits shorter than 30 days show linebroadening consistent with synchronized rotation, while about half theprimaries with periods in the range 30-120 days are synchronized. Tostudy the dependence of rotation on stellar evolution when tidal effectsare not important, we used a subsample of single stars and members inwide binaries. We found evidence to suggest that the first dredge-up mayplay a role in speeding up the rotation of the observable outer layersof giants and that the rotational velocity of horizontal branch stars islarger by a few km s-1 than that of first-ascent giants withsimilar mass, effective temperature, and radius. Finally, we found threegiants that rotate more rapidly than expected. We conjecture that theyacquired their excess angular momentum by ingesting planets.Some of the results presented here used observations made with theMultiple Mirror Telescope, a joint facility of the SmithsonianInstitution and the University of Arizona.
| 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.
| 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.
| 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.
| Effect of chromospheric activity on the mean colours of late-type stars. II. Is (B-V)0 also affected?
We confirm the existence of an ``excess'' in the mean dereddened(U-B)0 colour of active single-lined spectroscopic giantsover quiescent stars of the same spectral type and find evidence forthis ``excess'' in (B-V)0, although at a lower scale, whenplotted against (R-I)0. This result suggests that the use of(B-V)0 calibrations to determine fundamental parameters orspectral types for late-type active stars should be taken with caution.Since magnetic activity is definitely involved, these and similarcalibrations using (U-B)0 and/or (B-V)0 should notbe used for the study of late-type young clusters' members or late-typepre-main sequence stars without some consideration. Instead,near-infrared colours like (R-I)0 should be bettertemperature indicators for these stars.
| 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 photospheric abundances of active binaries. I. Detailed analysis of HD 113816 (IS Vir) and HD 119285 (V851 Cen)
The high-resolution optical spectra of the two X-ray active binaries RSCVn stars HD 113816 (IS Vir) and HD 119285 (V851 Cen) are analysed andtheir Na, Mg, Al, Si, Ca, Sc, Ti, Co and Ni contents determined, in theframework of a larger program of chemical analysis of RS CVn stellaratmosphere. The analysis of IS Vir and V851 Cen is performed with threedifferent LTE methods. In the first one, abundances are derived for alarge set of transitions (among which 28 Fe I lines, spanning a broadinterval in excitation potential and equivalent width, and 6 Fe IItransitions) using measured equivalent widths and Kurucz LTE modelatmospheres as input for the MOOG software package. The inputatmospheric parameters and abundances are iteratively modified until (i)the Fe I abundances exhibit no trend with excitation potential orequivalent width, (ii) Fe I and Fe II average abundances are the sameand (iii) Fe and Alpha elements average abundances are consistent withthe input values. The second method follows a similar approach, but usesa restricted line list (without the Fe I ``low excitation potential''transitions) and relies on the B-V and V-I colour indices to determinethe temperature. The third method uses the same restricted line list asthe second method and relies on fitting the 6162 Å Ca I line wingprofiles to derive the surface gravity. The reliability of these methodsis investigated in the context of single line RS CVn stars. It is shownthat the V-I photometric index gives, on a broader sample of stars,significantly cooler estimates of the effective temperature than the B-Vindex. All approaches give results in good agreement with each other,except the V-I based method. The analysis of IS Vir and V851 Cen resultsin both cases in their primaries being giant stars of near-solarmetallicity. Their parameters as derived with the first method arerespectively T_eff = 4720 K, log g = 2.65, [Fe/H] = +0.04 and T_eff =4700 K, log g = 3.0 and [Fe/H] = -0.13. In the case of V851 Cen thederived iron content is significantly higher than a previousdetermination in the literature. Both stars exhibit relativeoverabundances of several elements (e.g. Ca) with respect to the solarmix. Table 2 is only available in electronic form athttp://www.edpsciences.org
| The tidal effects on the lithium abundance of binary systems with giant component
We analyse the behavior of lithium abundance as a function of effectivetemperature, projected rotational velocity, orbital period andeccentricity for a sample of 68 binary systems with giant component andorbital period ranging from about 10 to 6400 days. For these binarysystems the Li abundances show a gradual decrease with temperature,paralleling the well established result for single giants. We have alsoobserved a dependence of lithium content on rotation. Binary systemswith moderate to high rotation present also moderate to high Li content.This study shows also that synchronized binary systems with giantcomponent seem to retain more of their original lithium than theunsynchronized systems. For orbital periods lower than 100 to 250 days,typically the period of synchronization for this kind of binary systems,lithium depleted stars seems to be unusual. The suggestion is made thatthere is an ``inhibited zone" in which synchronized binary systems withgiant component having lithium abundance lower than a threshold levelshould be unusual. Based on observations collected at ESO, La Silla.
| 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
| A catalog of rotational and radial velocities for evolved stars
Rotational and radial velocities have been measured for about 2000evolved stars of luminosity classes IV, III, II and Ib covering thespectral region F, G and K. The survey was carried out with the CORAVELspectrometer. The precision for the radial velocities is better than0.30 km s-1, whereas for the rotational velocity measurementsthe uncertainties are typically 1.0 km s-1 for subgiants andgiants and 2.0 km s-1 for class II giants and Ib supergiants.These data will add constraints to studies of the rotational behaviourof evolved stars as well as solid informations concerning the presenceof external rotational brakes, tidal interactions in evolved binarysystems and on the link between rotation, chemical abundance and stellaractivity. In this paper we present the rotational velocity v sin i andthe mean radial velocity for the stars of luminosity classes IV, III andII. Based on observations collected at the Haute--Provence Observatory,Saint--Michel, France and at the European Southern Observatory, LaSilla, Chile. Table \ref{tab5} also available in electronic form at CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| On X-Ray Variability in Active Binary Stars
We have compared the X-ray emissions of active binary stars observed atvarious epochs by the Einstein and ROSAT satellites in order toinvestigate the nature of their X-ray variability. The primary aim ofthis work is to determine whether or not active binaries exhibitlong-term variations in X-ray emission, perhaps analogous to theobserved cyclic behavior of solar magnetic activity. We find that, whilethe mean level of emission of the sample remains steady, comparison ofdifferent ROSAT observations of the same stars shows significantvariation on timescales <~2 yr, with an ``effective variability''ΔI/I=0.32+/-0.04, where I and ΔI represent the mean emissionand variation from the mean emission, respectively. A comparison of theROSAT All-Sky Survey and later pointed observations with earlierobservations of the same stars carried out with Einstein yields onlymarginal evidence for a larger variation (ΔI/I=0.38+/-0.04 forEinstein vs. ROSAT All-Sky Survey and 0.46+/-0.05 for Einstein vs. ROSATpointed) at these longer timescales (~10 yr), thus indicating thepossible presence of a long-term component to the variability. Whetheror not this long-term component is due to the presence of cyclicvariability cannot be decided on the basis of existing data. However,assuming that this component is analogous to the observed cyclicvariability of the Sun, we find that the relative magnitude of thecyclic component in the ROSAT passband can, at most, be a factor of 4,i.e., I_cyc/I_min<4. This is to be compared with the correspondingbut significantly higher solar value of ~10-10^2 derived from GOES,Yohkoh, and Solrad data. These results are consistent with thesuggestions of earlier studies that a turbulent or distributive dynamomight be responsible for the observed magnetic activity on the mostactive, rapidly rotating stars.
| Radio star catalogue observed in San Juan (RSSJ95)
Using the data observed in San Juan with the photoelectric AstrolabeMark II of the Beijing Astronomical Observatory from February, 1992 toMarch, 1997, the radio star catalogue in San Juan(RSSJ95) has beencompiled. There are 69 radio stars in this catalogue. The positions ofthe radio stars are for the epoch of observation and the equinox J2000.0and a system close to that of the system FK5. The mean precisions are+/-2.2 ms and +/-0.035'' in right ascensions and declinations,respectively. The magnitudes of stars are from 0.9 to 10.7. Thedeclinations are from -2fdg 5 to -60(deg) . The mean epoch is 1995.1.Finally, the comparison results between the Hipparcos catalogue andRSSJ95 are given.
| The age-mass relation for chromospherically active binaries. III. Lithium depletion in giant components
We present a study of the lithium abundances of a sample of evolvedcomponents of Chromospherically Active Binary Systems. We show that asignificant part of them have lithium excesses, independently of theirmass and evolutionary stage. Therefore, it can be concluded that Liabundance does not depend on age for giant components of CABS. Theseoverabundances appear to be closely related to the stellar rotation, andwe interpret them as a consequence of the transfer of angular momentumfrom the orbit to the rotation as the stars evolve in and off the MainSequence, in a similar way as it happens in the dwarf components of thesame systems and in the Tidally Locked Binaries belonging to the Hyadesand M67. Based on observations collected with the 2.2\,m telescope ofthe German-Spanish Observatorio de Calar Alto (Almeria, Spain), and withthe 2.56\,m Nordic Optical Telescope in the Spanish Observatorio delRoque de los Muchachos of the Instituto de Astrof\'\i sica de Canarias(La Palma, Spain)
| Long-term monitoring of active stars. VIII. UBV(RI)_(c) photometry collected in February 1992
As a part of an extensive program focusing on the global properties andevolution of active stars, high-precision UBV(RI)_c photometry of 31selected stars, collected at the European Southern Observatory over the14-29 February 1992 interval, is presented. Significant evolution of thelight curves, period variations and evidence for long-term variabilityof the global degree of spottedness are found. Some spectralclassifications are revised and the inferred photometric parallaxes arecompared, whenever possible, with the values measured by the Hipparcossatellite. Flare events were detected for the star HD16157 = CC Eri, EXO 055609-3804.4 TY Coland HD 119285 = V851 Cen. Optical variability wasdiscovered for the Pop II binary HD 89499. Theseobservations contribute to the establishment of a time-extendedphotometric database which can give important clues on topics such asthe stability of spotted areas, differential rotation, solar-like cyclesand the correlation between inhomogeneities at different atmosphericlevels. based on data collected at the European Southern Observatory, LaSilla, Chile.
| On the rotation-activity correlation for active binary stars
We present an investigation of rotation-activity correlations usingInternational Ultraviolet Explorer (IUE) SWP measurements of the Civemission line at 1550Angstroms for 72 active binary systems. We use astandard stellar evolution code to derive non-empirical Rossby numbers,R_0, for each star in our sample and compare the resulting Civrotation-activity correlation to that found for empirically derivedvalues of the Rossby number and that based on rotation alone. For dwarfstars our values of R_0 do not differ greatly from empirical ones and wefind a corresponding lack of improvement in correlation. Only a marginalimprovement in correlation is found for evolved components in oursample. We discuss possible additional factors, other than rotation orconvection, that may influence the activity levels in active binaries.Our observational data imply, in contrast to the theoretical predictionsof convective motions, that activity is only weakly related to mass inevolved stars. We conclude that current dynamo theory is limited in itsapplication to the study of active stars because of the uncertainty inthe angular velocity-depth profile in stellar interiors and the unknowneffects of binarity and surface gravity.
| Long-term monitoring of active stars. VII. UBV(RI)_c photometry collected in March 1991
In the framework of an extensive program focusing on the globalproperties and evolution of active stars, high-precision UBV(RI)_cphotometry of 19 selected stars, collected at the European SouthernObservatory over the 15-31 March 1991 interval is presented. Significantevolution of the light curves, period variations and evidence forlong-term variability of the global degree of spottedness are found.Most of the spectral classifications are discussed. A flare event wasdetected for the star HD 127535 = V 841 Cen. These observationscontribute to the establishment of a time-extended photometric databasewhich can give important clues on topics such as the stability ofspotted areas, differential rotation, solar-like cycles and thecorrelation between inhomogeneities at different atmospheric levelsFigure 1 to 24 are only available on the on-line version of A&A athttp://www.ed-phys.fr}. based on data collected at the European SouthernObservatory, La Silla, Chile. Tables and the complete data set are alsoavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr or via http://cdsweb.u-strasbg.fr/Abstract.html
| San Juan radio star catalogue and comparison with HIPPARCOS catalogue.
Not Available
| Accurate Positions for Radio Stars as Determined from CCD Observations in the Extragalactic Reference Frame.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....114.1679S&db_key=AST
| HIPPARCOS distances of X-ray selected stars: implications on their nature as stellar population.
We present the parallaxes, measured by Hipparcos, for a sample of X-rayselected stars. The stars belong to the stellar sample of the EinsteinExtended Medium Sensitivity Survey. They are all at galactic latitude|b|>20deg, and are generally far away from known star formingregions. Several of these stars show lithium abundance and activitylevel typical of very young stars with ages comparable to that of thePleiades. We show that the majority of our sample stars are on the mainsequence, with only =~20% being giants. We do not find a significantpresence of pre-main sequence stars in our sample, notwithstanding thefact that some of our stars have a considerable lithium abundance,showing that the stars observed are most likely young and activemain-sequence objects.
| EUV Emission from RS Canum Venaticorum binaries.
We performed a study of 104 RS CVn systems in the extreme ultraviolet(EUV) using the all-sky survey data obtained by the Extreme UltravioletExplorer (EUVE). The present sample includes several new RS CVndetections; 11 more than in the published EUVE catalogs, and 8 more thanin the ROSAT Wide Field Camera catalog. The ratio of detections tonon-detections remained constant throughout the sky, implying that ourdetections are not limited by the exposure time but are most likelylimited by absorption from the interstellar medium. A general trend ofincreasing Lex/B (50-180Å) flux with decreasing rotational periodis clear. The dwarf systems exhibit a leveling-off for the fasterrotators. In contrast, the evolved systems exhibit no such effect. Forthe RS CVn systems the losses in the EUV represent a smaller fraction ofthe coronal radiative losses, as compared to active late-type dwarfs.
| Long-term monitoring of active stars. V. UBV(RI)_ c_ photometry collected in Feb.-Mar. 1990.
High-precision UBV(RI)_c_ photometry of 12 selected active stars,collected at the European Southern Observatory (La Silla, Chile) overthe period February - March 1990, is presented. Significant evolution ofthe light curves, period variations and, in most cases, evidence forlong-term variability of the global degree of spottedness are found.Some of the spectral classifications are discussed. This paper is partof a more extensive program focusing on the global properties andevolution of active stars and is aimed at establishing a time-extendedphotometric database which can give important clues on topics such asthe stability of the spotted areas, differential rotation and solar-likecycles.
| The behaviour of the excess CA II H and K and Hɛ emissions in chromospherically active binaries.
In this work we analyze the behaviour of the excess Ca II H and K andHɛ emissions in a sample of 73 chromospherically active binarysystems (RS CVn and BY Dra classes), of different activity levels andluminosity classes. This sample includes the 53 stars analyzed byFernandez-Figueroa et al. (1994) and the observations of 28 systemsdescribed by Montes et al. (1995c). By using the spectral subtractiontechnique (subtraction of a synthesized stellar spectrum constructedfrom reference stars of spectral type and luminosity class similar tothose of the binary star components) we obtain the active-chromospherecontribution to the Ca II H and K lines in these 73 systems. We havedetermined the excess Ca II H and K emission equivalent widths andconverted them into surface fluxes. The emissions arising from eachcomponent were obtained when it was possible to deblend bothcontributions. We have found that the components of active binaries aregenerally stronger emitters than single active stars for a giveneffective temperature and rotation rate. A slight decline of the excessCa II H and K emissions towards longer rotation periods, P_rot_, andlarger Rossby numbers, R_0_, is found. When we use R_0_ instead ofP_rot_ the scatter is reduced and a saturation at R_0_=~0.3 is observed.A good correlation between the excess Ca II K and Hɛchromospheric emission fluxes has been found. The correlations obtainedbetween the excess Ca II K emission and other activity indicators, (C IVin the transition region, and X-rays in the corona) indicate that theexponents of the power-law relations increase with the formationtemperature of the spectral features.
| A Search for Optical Flares in Chromospherically Active Stars
We have surveyed four years of archival UBV photometry of 69chromospherically active stars obtained with the Phoenix-10 automaticphotoelectric telescope in search of optical flares on these stars. Wedemonstrate taht, while flares can be detected in these data, the numberof events observed on evolved stars remains very small. Flares werefound only on UX Arietis, II Pegasi, and AR Piscium. (SECTION: Stars)
| The emission of the RS CVn binaries in the IRAS passbands.
In the literature, there is an ambiguity pertaining to the existence ofa far-IR excess in RS CVn systems. In the current paper we undertook astudy of the behaviour of 103 such systems in the IRAS passbands. Wefound 72 acceptable detections in the 12μm band, and 40 in the25μm band (50% more than the IRAS Point Source Catalog). Although ourfindings may be interpreted as indicating towards the existence of anexcess beyond 12μm for some systems, the evidence is not conclusivein all but two cases. These are systems GX Lib and HR 7428, with Capellabeing the only system where the IRAS fluxes in all four bands originatefrom the stellar photosphere. Given the accuracy of the data we did notfind 12μm excess for any system. We argue that the IRAS data alonecannot settle the issue, as their uncertainty is, in many cases, higherthan what the Signal-to-Noise ratio of each observation implies.Furthermore, at the higher wavelength bands the IRAS angular resolutiondrops from 0.5' at 12μm to 2' at 100μm and the background becomesvery complex, so one cannot be certain about the origin of the observedflux. The existence of IR excess in the RS CVn stars is important as faras the evolutionary scenarios for these systems are concerned. Futuremissions such as the Infrared Space Observatory will return moresensitive and accurate measurements and the ambiguity can be removed.The fluxes we quote will be helpful when planning these futureobservations, as we provide more accurate photometry and for a largerselection of sources than the IRAS Point Source Catalog.
| Application of the spectral subtraction technique to the CA II H & K and Hɛ lines in a sample of chromospherically active binaries.
We present new spectroscopic observations in the Ca II H & K lineregion for a sample of 28 chromospherically active binary systems (RSCVn and BY Dra classes), with different activity levels. By using thespectral subtraction technique (subtraction of a synthesized stellarspectrum constructed from reference stars of similar spectral type andluminosity class) we obtain the active-chromosphere contribution to theCa II H & K lines and to the Hɛ line when it is present. Wehave compared the emission equivalent widths obtained with thistechnique with those obtained by reconstruction of the absorption lineprofile below the emission peak(s). The emissions arising from eachindividual star were obtained when it was possible to deblend thecontribution of both components. The Ca II line profiles correspondingto different seasons and orbital phases are analysed in order todetermine the contribution of each component and to study thechromospheric activity variations.
| 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.
| The Einstein Extended Medium-Sensitivity Survey Second Epoch: Results for the Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJS...99..701F&db_key=AST
| The space density of active binaries from X-ray surveys.
We review the currently available data on active binaries selected fromEinstein observatory based X-ray surveys, and compare the inferred spacedensity with the available estimates based on optically selectedsamples. It is shown that, in contrast to previous reports, nodisagreement is present between the optical and X-ray based estimates,and that the space density of active binaries is likely to be smallerthan previous estimates based on X-ray selected data. In particular, weshow that of the 18 systems in the δ>-20deg subsample of theEinstein Extended Medium Sensitivity Survey previously classified asactive binaries, 6 are not to be considered as such, while a further 5have a somewhat doubtful status. The total space density we derive is7.7x10^-5^pc^-3^ if the 5 doubtful systems are retained and3.7x10^-5^pc^-3^ if they are excluded. Both values are substantiallylower than the value of 4.5x10^-4^pc^-3^ originally derived from thesame subsample of Extended Medium Sensitivity Survey fields. Also, themedian X-ray luminosity of X-ray selected active binaries is found to behigher than previously reported, and again in contrast with previousreports, we find no disagreement between the X-ray luminosities of X-rayand optically selected samples. We briefly discuss the implication ofthe revised value of the space density on the contribution of activebinaries to the soft X-ray background.
| Suspected Starspots Found on the K Giants in Seven Ellipsoidal RS CVn-Type Binaries
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995AJ....109.2177K&db_key=AST
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | מאזניים |
| התרוממות ימנית: | 15h23m26.06s |
| סירוב: | -06°36'37.8" |
| גודל גלוי: | 7.354 |
| מרחק: | 95.147 פארסק |
| תנועה נכונה: | -2.5 |
| תנועה נכונה: | -122.3 |
| B-T magnitude: | 8.676 |
| V-T magnitude: | 7.464 |
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