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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.
| 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.
| New periodic variables from the Hipparcos epoch photometry
Two selection statistics are used to extract new candidate periodicvariables from the epoch photometry of the Hipparcos catalogue. Theprimary selection criterion is a signal-to-noise ratio. The dependenceof this statistic on the number of observations is calibrated usingabout 30000 randomly permuted Hipparcos data sets. A significance levelof 0.1 per cent is used to extract a first batch of candidate variables.The second criterion requires that the optimal frequency be unaffectedif the data are de-trended by low-order polynomials. We find 2675 newcandidate periodic variables, of which the majority (2082) are from theHipparcos`unsolved' variables. Potential problems with theinterpretation of the data (e.g. aliasing) are discussed.
| 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.
| Interstellar polarization at high galactic latitudes from distant stars. V. First results for the South Galactic Pole
We present the first results of our interstellar polarization programmefor the South Galactic Pole (b<-70degr ). The new observations (43stars) combined with previously published data show that there is asubstantial interstellar polarization in this area of the sky. Startingat a distance of 300 pc, we have found stars with P > 0.3% includingone for which P ~ 0.6%. These measurements lead to the conclusion thatthere is a significant amount of interstellar dust at high southgalactic latitudes. Futhermore, there is a remarkable alignment seenover the South Polar Cap: for most stars the directions of polarizationvectors are aligned with the longitude l ~ 80degr , close to theexpected direction of the global magnetic field. In this respect the SGPseems to differ strongly from its northern counterpart.
| 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.
| 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)
| Multiwavelength optical observations of chromospherically active binary systems. I. Simultaneous H alpha, NA i D1, D2, and He i D3 observations
This is the first paper of a series aimed at studying the chromosphereof active binary systems using the information provided for severaloptical spectroscopic features. Simultaneous H alpha, Na iD1, D2, and He i D3 spectroscopicobservations are reported here for 18 systems. The chromosphericcontribution in these lines have been determined using the spectralsubtraction technique. Very broad wings have been found in thesubtracted H alpha profile of some of the more active stars. Theseprofiles are well matched using a two-components Gaussian fit (narrowand broad) and the broad component could be interpreted as arising frommicroflaring. Prominence-like extended material have been detected in anear-eclipse H alpha observation of the system AR Lac. The excessemission found in the Na i D1 and D2 lines byapplication of the spectral subtraction technique and the behaviour ofthe H alpha line in the corresponding simultaneous observations indicatethat the filling-in of the core of these lines is a chromosphericactivity indicator. For giant stars of the sample the He i D3line has been detected in absorption in the subtracted spectra. Anoptical flare has been detected in UX Ari and II Peg through thepresence of the He i D3 in emission in coincidence with theenhancement of the H alpha emission. Based on observations made with theIsaac Newton telescope operated on the island of La Palma by the RoyalGreenwich Observatory at the Spanish Observatorio del Roque de LosMuchachos of the Instituto de Astrofisica de Canarias.
| Rotational Velocities of Late-Type Stars
A calibration based on the results of Gray has been used to determineprojected rotational velocities for 133 bright stars with spectral typesof F, G, or K, most of which appear in {\it The Bright Star Catalogue}.The vast majority have {\it v} sin {\it i} $\leq$ 10 km s$^{-1}$ and,thus, are slow rotators. With the new calibration, projected rotationalvelocities have been determined for a sample of 111 late-type stars,most of which are chromospherically active. Some of the stars have hadtheir rotational velocities measured for the first time. (SECTION:Stars)
| The ROSAT All-Sky Survey of Active Binary Coronae. III. Quiescent Coronal Properties for the BY Draconis--Type Binaries
We present X-ray observations of 35 active late-type BY Draconis dwarfbinary systems and 28 evolved binary systems, similar in nature to theRS Canum Venaticorum systems, obtained with the Position SensitiveProportional Counter (PSPC) during the ROSAT All-Sky Survey phase of themission. Of this sample, 52 targets were detected in exposures ofroughly 600 s or less. When these new data are combined with the earlierresults from Dempsey et al. (1993b), this survey represents the largestsample of active binary systems observed to date at any wavelength,including X-rays. We expand our investigation of how coronal properties(e.g., surface flux, luminosity, etc.) correlate with stellar parameters(e.g., rotation period, color, etc.) and confirm the conclusions ofDempsey et al. (1993b). Rotation period provides the best correlationwith X-ray surface flux with F_{{X}}~P^{-0.59+/-0.10}_{{rot}} for theentire sample. We find no evidence for a "basal" or nonmagnetic X-rayflux component. We model the low-resolution pulse-height spectra for 12systems with two-temperature thermal plasmas. The derived temperaturesfor the BY Dra systems are identical to those previously derived foractive evolved giants and subgiants in close binaries (Dempsey et al.1993c). We also show that the dependence of temperature and emissionmeasures on rotation period is the same for the dwarf, subgiant, andgiant binaries.
| 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.
| 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.
| 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.
| Radio continuum emission from stars: a catalogue update.
An updated version of my catalogue of radio stars is presented. Somestatistics and availability are discussed.
| Are the Rotational Axes Perpendicular to the Orbital Planes in the Binary Systems? II. Synchronous Long-Period RS CVn Stars
Inclinations of the rotational axes, irot, are determined for37 synchronous long-period RS CVn binaries by combining v sin imeasurements with rotational period information. These inclinations arethen compared with the orbital inclinations of the systems,iorb, to test the alignment between the equatorial andorbital planes. Contrary to the asynchronous RS CVn systems (see PaperI), in all 37 cases irot is equal or nearly equal toiorb, and the assumption about coplanarity of theirequatorial and orbital planes is justified.
| The Wilson-Bappu effect and other CA II H and K line parameters relationships in chromospherically active binaries
We present measurements of the emission core width W_0_ and thewavelength separation of the K_1_ dips, W_1_, of the Ca II H and Kemission lines observed on high-dispersion spectra of 28chromospherically active binary systems (RS CVn and BY Dra stars) and 18single active stars. We test the width-luminosity correlations (theWilson-Bappu (WB) effect, and (W_1_, M_V_)) in these very active starsand analyse the influence of the activity level (I_K_3__) and therotational broadening (Vsin i) in these correlations. We have found thatfor very active stars the emission widths, both W_0_ and W_1_, arelarger than expected from previously accepted width-luminosityrelations. The stars with strong emission intensities, I_K_3__, andlarge values of Vsin i seem to present larger values of W_0_ thanresulted from WB relation, the effect of the rotational velocity beingthe most remarkable. On the contrary, W_1_ is strongly influenced byI_K_3__ but the effect of the rotational broadening is lesser. We alsoanalyse the behaviour of the Ca II H and K line parameters in these veryactive stars in relation with less active stars and we found that theincrease of W_1_ and I_K_1__ with I_K_3__ presents a flattening for themost active stars which is different for each value of W_0_. Finally wealso find a Hɛ width-luminosity correlation in the stars of thesample in which this emission line is present.
| Lithium in Rs-Canum Binaries and Related Chromospherically Active Stars - Part Three - Northern Rs-Canum Systems
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1994A&A...283..893R&db_key=AST
| The active dynamo stars: RS CVn, BY Dra, FK Com, Algol, W UMa, and T Tau
Not Available
| A catalog of chromospherically active binary stars (second edition)
The catalog contains 206 spectroscopic binary systems with at least onelate-type component that shows Ca II H and K emission in its spectrum.These systems include the classical RS CVn binaries and BY Dra binaries.The catalog summarizes information on the photometric, spectroscopic,orbital, and physical properties of the systems as well as space motionsand positions. Up to 42 'parameters' for each stellar system are listedfollowed by the appropriate reference to direct interested colleagues tothe original papers. A comprehensive selection of further informationfor each star is given in the individual notes. In addition, the catalogcontains a candidate list of 138 stars that have similar characteristicsbut are not definitely known binaries or have not had Ca II H and Kemission observed.
| The ROSAT All-Sky Survey of active binary coronae. I - Quiescent fluxes for the RS Canum Venaticorum systems
One hundred and thirty-six RS CV(n) active binary systems were observedwith the ROSAT Position Sensitive Proportional Counter (PSPC) during theAll-Sky Survey component of the mission. The entire sky was surveyed,which represents the largest sample of RS CV(n) systems observed to dateat any wavelength, including X-rays. X-ray surface fluxes for the RSCV(n) systems are found to lie in the range 10 exp 4 to 10 exp 8 ergs/sqcm seconds. Surface flux as a function of (B - V) color is reported. Adecrease in surface flux with increasing rotation period for the entiresample is observed. The rotation period provides the best stellar ororbital parameter to predict the X-ray surface flux level. The absenceof correlation of F(x) or L(x) with Gamma is noted due to the fact thatthe coronal heating mechanism for these active stars must be magnetic incharacter, and the magnetic field depends on the interaction betweenconvection and differential rotation inside the star. X-ray propertiesof the RS CV(n) systems with 6 cm radio and C IV UV emission systems iscompared.
| Lithium in Rs-Canum Binaries and Related Chromospherically Active Stars - Part Two - Spectrum Synthesis Analysis
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&A...273..194R&db_key=AST
| Statistical Analysis of a Sample of Spectroscopic Binaries Containing Late Type Giants
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&A...271..125B&db_key=AST
| Lithium abundance and activity for 57 RS CVn systems
The high resolution (0.049-0.145Å) and high signal-to-noise ratio(100-600) Reticon and CCD spectra of 57 binaries of the RS CVn type wereobtained with the coudé spectrograph of the McDonald Observatory2.1m telescope and the Yunnan Observatory 1m telescope for an analysisof the correlation between Li abundance and chromospheric activity. TheLi abundance of 57 RS CVn systems, which include 76 detected components,has been determined through the observed equivalent widths of the Lidoublet (6707.761Å + 6707.912Å) and Kurucz's modelatmospheres. By the method of the comprehensive analysis of theatmospheric model the abundances of [Fe/H], [Ti/Fe] and logN(Li) havebeen calculated for 10 of the above mentioned binaries. We have madestatistical analysis of the correlations between the lithium abundanceand the effective temperature Teff as well as the projectedrotational velocity, v sin i. The results show that the Li abundancetends to decrease with the drop of Teff. On the other hand,the Li abundance has a tendency to decrease with the increase of v sini, but the dispersion of this correlation is very large. In particular,in the range of v sin i < 25km/sec we may say that no correlationexists at all. Besides, a statistical analysis shows that there is noevident relation between the Li abundance of 57 binaries of the RS CVntype and the level of activity. However, it is worthwhile to note thatthe Li abundances of the cold components in 7 binary systems during theperiod of strong activity are lower than those of the less active hotcomponents. The opposite case has never been found.
| Lithium abundance and activity for 57 RS CVn systems
The correlation between Li abundance and chromospheric activity isanalyzed in high-resolution, high SNR spectra of 57 RS CVn typebinaries. Lithium abundances of 87 RS CVn components for 57 RS CVnsystems is obviously reduced with decreasing gradual reduction inT(eff). Li abundance shows statistically declining trends in RS CVnstars with increasing rotational velocities. Most of the RS CVn systemsare unlikely to be metal-poor stars. The Li abundance in the RS CVnstars appears to have no obvious correlation with chromosphericactivity.
| Kinematics and age of RS Canum Venaticorum and by Draconis stars
Space velocities of 146 chromospherically active binary stars have beencalculated. Containing F-M spectral types on the main sequence togetherwith G and K giants and subgiants, this very heterogeneous sample hasbeen divided into groups in order to segregate stars which have similarkinematics and ages. After many trials for different criteria, thesample was divided into five groups - two groups for giants, two groupsfor main-sequence systems, and one group for main-sequence systems.Kinematics of subgiants implies a stellar age of about 2-3 Gyr. Youngand old groups of giants and main-sequence systems could becharacterized by a kinematical age of about 1 Gyr and more than 5 Gyr,respectively. These ages are estimated approximately according to spacevelocity distributions and dispersions in velocity space in each group.Inferred ages for the groups above agrees with circulation, rotationactivity relation, and stellar evolution theories.
| Lithium in RS CVn binaries and related chromospherically active stars. I - Observational results
The present survey of the Li I 6708 A line in a sample of spectral typeG and K stars with luminosity classes III, IV, and V shows that manyK-type stars in the sample, including a large number of RS CVn binaries,show an anomalously high Li abundance relative to typical inactive starsof the same spectral type. Only a few stars in the sample are likely tobe premain sequence objects of stars which have recently arrived on themain sequence. Mechanisms that could lead to the enhanced Li absorptionin chromospherically active stars are discussed; these encompass largecool spots on the stellar surface, the production of Li in stellarflares by spallation reactions, and the evolution from main-sequenceprogenitors without, or with very shallow, outer convective zones.
| A uvby-beta survey of northern-hemisphere active binaries. II - The m1 deficiency
New photometric observations, using the uvby and H-beta systems of 72northern-hemisphere active binaries are discussed in order to explainthe main characteristics of their spectral light intensity distribution.Values of the parameter delta(m1) range from 0.0 to 0.3 mag, whichcannot be explained in terms of metal underabundance alone. Theexistence of some mechanism responsible for such a color-index anomalyis thus suggested and is found to be in close relation with the involveddegree of solar-type activity.
| Chromospheric CA II H and K and H-alpha emission in single and binary stars of spectral types F6-M2
New observations of the Ca II H and K and H-epsilon region and/or theBalmer H-alpha line are presented for 100 mostly very active stars butalso for weak or inactive stars with suspected activity. Correlationsbetween chromospheric activity at Ca II H and K and H-alpha andeffective surface temperature and rotation are identified, and severalnew stars with chromospheric Ca II H and K emission are discovered. Nosingle activity-rotation relation can be derived for all luminosityclasses, and there is clear evidence that evolved stars are generallymore active than main-sequence stars of the same rotation period. Binarywithin the evolved stars appears to play no role, while main-sequencebinary stars show generally higher levels of activity than their singlecounterparts. Chromospheric emission in the Ca II H and K lines dependson surface temperature in that flux declines with cooler temperature.
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Observation and Astrometry data
| Constellation: | Κήτος |
| Right ascension: | 00h22m46.34s |
| Declination: | -09°13'51.1" |
| Apparent magnitude: | 7.968 |
| Distance: | 416.667 parsecs |
| Proper motion RA: | 5.5 |
| Proper motion Dec: | -45.7 |
| B-T magnitude: | 9.406 |
| V-T magnitude: | 8.087 |
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INHABITED SKY
