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Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters
The availability of the Hipparcos Catalogue has triggered many kinematicand dynamical studies of the solar neighbourhood. Nevertheless, thosestudies generally lacked the third component of the space velocities,i.e., the radial velocities. This work presents the kinematic analysisof 5952 K and 739 M giants in the solar neighbourhood which includes forthe first time radial velocity data from a large survey performed withthe CORAVEL spectrovelocimeter. It also uses proper motions from theTycho-2 catalogue, which are expected to be more accurate than theHipparcos ones. An important by-product of this study is the observedfraction of only 5.7% of spectroscopic binaries among M giants ascompared to 13.7% for K giants. After excluding the binaries for whichno center-of-mass velocity could be estimated, 5311 K and 719 M giantsremain in the final sample. The UV-plane constructed from these datafor the stars with precise parallaxes (σπ/π≤20%) reveals a rich small-scale structure, with several clumpscorresponding to the Hercules stream, the Sirius moving group, and theHyades and Pleiades superclusters. A maximum-likelihood method, based ona Bayesian approach, has been applied to the data, in order to make fulluse of all the available stars (not only those with precise parallaxes)and to derive the kinematic properties of these subgroups. Isochrones inthe Hertzsprung-Russell diagram reveal a very wide range of ages forstars belonging to these groups. These groups are most probably relatedto the dynamical perturbation by transient spiral waves (as recentlymodelled by De Simone et al. \cite{Simone2004}) rather than to clusterremnants. A possible explanation for the presence of younggroup/clusters in the same area of the UV-plane is that they have beenput there by the spiral wave associated with their formation, while thekinematics of the older stars of our sample has also been disturbed bythe same wave. The emerging picture is thus one of dynamical streamspervading the solar neighbourhood and travelling in the Galaxy withsimilar space velocities. The term dynamical stream is more appropriatethan the traditional term supercluster since it involves stars ofdifferent ages, not born at the same place nor at the same time. Theposition of those streams in the UV-plane is responsible for the vertexdeviation of 16.2o ± 5.6o for the wholesample. Our study suggests that the vertex deviation for youngerpopulations could have the same dynamical origin. The underlyingvelocity ellipsoid, extracted by the maximum-likelihood method afterremoval of the streams, is not centered on the value commonly acceptedfor the radial antisolar motion: it is centered on < U > =-2.78±1.07 km s-1. However, the full data set(including the various streams) does yield the usual value for theradial solar motion, when properly accounting for the biases inherent tothis kind of analysis (namely, < U > = -10.25±0.15 kms-1). This discrepancy clearly raises the essential questionof how to derive the solar motion in the presence of dynamicalperturbations altering the kinematics of the solar neighbourhood: doesthere exist in the solar neighbourhood a subset of stars having no netradial motion which can be used as a reference against which to measurethe solar motion?Based on observations performed at the Swiss 1m-telescope at OHP,France, and on data from the ESA Hipparcos astrometry satellite.Full Table \ref{taba1} is only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/430/165}
| 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 Rotation of Binary Systems with Evolved Components
In the present study we analyze the behavior of the rotational velocity,vsini, for a large sample of 134 spectroscopic binary systems with agiant star component of luminosity class III, along the spectral regionfrom middle F to middle K. The distribution of vsini as a function ofcolor index B-V seems to follow the same behavior as their singlecounterparts, with a sudden decline around G0 III. Blueward of thisspectral type, namely, for binary systems with a giant F-type component,one sees a trend for a large spread in the rotational velocities, from afew to at least 40 km s-1. Along the G and K spectral regionsthere are a considerable number of binary systems with moderate tomoderately high rotation rates. This reflects the effects ofsynchronization between rotation and orbital motions. These rotatorshave orbital periods shorter than about 250 days and circular or nearlycircular orbits. Except for these synchronized systems, the largemajority of binary systems with a giant component of spectral type laterthan G0 III are composed of slow rotators.
| Absolute proper motions of open clusters. I. Observational data
Mean proper motions and parallaxes of 205 open clusters were determinedfrom their member stars found in the Hipparcos Catalogue. 360 clusterswere searched for possible members, excluding nearby clusters withdistances D < 200 pc. Members were selected using ground basedinformation (photometry, radial velocity, proper motion, distance fromthe cluster centre) and information provided by Hipparcos (propermotion, parallax). Altogether 630 certain and 100 possible members werefound. A comparison of the Hipparcos parallaxes with photometricdistances of open clusters shows good agreement. The Hipparcos dataconfirm or reject the membership of several Cepheids in the studiedclusters. Tables 1 and 2 are only 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
| 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
| The effective temperature scale of giant stars (F0-K5). I. The effective temperature determination by means of the IRFM
We have applied the InfraRed Flux Method (IRFM) to a sample ofapproximately 500 giant stars in order to derive their effectivetemperatures with an internal mean accuracy of about 1.5% and a maximumuncertainty in the zero point of the order of 0.9%. For the applicationof the IRFM, we have used a homogeneous grid of theoretical modelatmosphere flux distributions developed by \cite[Kurucz (1993)]{K93}.The atmospheric parameters of the stars roughly cover the ranges: 3500 K<= T_eff <= 8000 K; -3.0 <= [Fe/H] <= +0.5; 0.5 <= log(g) <= 3.5. The monochromatic infrared fluxes at the continuum arebased on recent photometry with errors that satisfy the accuracyrequirements of the work. We have derived the bolometric correction ofgiant stars by using a new calibration which takes the effect ofmetallicity into account. Direct spectroscopic determinations ofmetallicity have been adopted where available, although estimates basedon photometric calibrations have been considered for some stars lackingspectroscopic ones. The adopted infrared absolute flux calibration,based on direct optical measurements of stellar angular diameters, putsthe effective temperatures determined in this work in the same scale asthose obtained by direct methods. We have derived up to fourtemperatures, TJ, TH, TK and T_{L'},for each star using the monochromatic fluxes at different infraredwavelengths in the photometric bands J, H, K and L'. They show goodconsistency over 4000 K, and there is no appreciable trend withwavelength, metallicity and/or temperature. We provide a detaileddescription of the steps followed for the application of the IRFM, aswell as the sources of error and their effect on final temperatures. Wealso provide a comparison of the results with previous work.
| Catalogs of temperatures and [Fe/H] averages for evolved G and K stars
A catalog of mean values of [Fe/H] for evolved G and K stars isdescribed. The zero point for the catalog entries has been establishedby using differential analyses. Literature sources for those entries areincluded in the catalog. The mean values are given with rms errors andnumbers of degrees of freedom, and a simple example of the use of thesestatistical data is given. For a number of the stars with entries in thecatalog, temperatures have been determined. A separate catalogcontaining those data is briefly described. Catalog only available atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Evolutionary Oddities in Old Disk Population Clusters
With a luminosity zero point fixed by the kinematics of old disksuperclusters (HR 1614, t = 6 Gyr, [Fe/H] = +0.1 dex) and groups(Arcturus, t = 14 Gyr, [Fe/H] = -0.65 dex), the luminosities and colorsof evolved old disk stars, especially red horizontal branch (RHB), earlyasymptotic branch [AGB(1)], thermally pulsing asymptotic giant branch[AGB(2)], and sdOB stars in old disk clusters (NGC 6791, 47 Tuc, M71,M67, Mel 66, NGC 2420, NGC 2204, and NGC 2443) are discussed. (1) TheRHB stars in the old disk all have M_V = +0.7 +/- 0.1 (M_K = -1.3 +/-0.1) mag. (2) Large-amplitude red variables (LARVs) with quasi-stableperiods and light curves are old disk stars on AGB(2). (3) AGB(1)objects include CH stars and semiregular (SRa) variables. (4) Thepopulous and overabundant cluster NGC 6791 may be the only disk clusterwith sdOB stars, populating the lower portion of the bifurcated extendedhorizontal branch that is usual in most ``blue tailed'' and high-densityhalo clusters. (5) Post-red giant branch (RGB) stars in old diskclusters show a B - V (b - y) defect when compared with RGB stars,possibly because of a change in the character of the atmospheres. (6) Ifthe bulk of the LARVs are pulsating in the fundamental mode, R Vir (P =145 days) is possibly a first-overtone pulsator. (7) The overabundantold disk clusters are within the solar circle, with Liller 1 being atthe Galactic center. (8) Several probable RHB stars at the southGalactic pole are identified. (9) The period-age relation, combined withthe known spatial distribution of Galactic LARVs, leads to a relationbetween age and scale height of distribution that monotonicallyincreases with age, leaving no obvious reason for a bifurcation of thepopulation.
| Broad-band JHK(L') photometry of a sample of giants with 0.5 > [Fe/H] > -3
We present the results of a three-year campaign of broad-band photometryin the near-infrared J, H, K and L' bands for a sample of approximately250 giant stars carried out at the Observatorio del Teide (Tenerife,Spain). Transformations of the Telescopio Carlos Sanchez systeminto/from several currently used infrared systems are extended to theredward part of the colour axis. The linearity of our photometric systemin the range -3 mag [Fe/H] >-3. Data of comparable quality previouslypublished have been added to the sample in order to increase thereliability of the relations to be obtained. We also provide mean IRcolours for giant stars according to spectral type.ables 1, 2 and 3 are only available in electronic form via the CDS(anonymous ftp 130.79.128.5 or http://cdsweb.u-strasbg.fr/Abstract.html
| The Hyades: distance, structure, dynamics, and age
{We use absolute trigonometric parallaxes from the Hipparcos Catalogueto determine individual distances to members of the Hyades cluster, fromwhich the 3-dimensional structure of the cluster can be derived.Inertially-referenced proper motions are used to rediscuss distancedeterminations based on convergent-point analyses. A combination ofparallaxes and proper motions from Hipparcos, and radial velocities fromground-based observations, are used to determine the position andvelocity components of candidate members with respect to the clustercentre, providing new information on cluster membership: 13 newcandidate members within 20 pc of the cluster centre have beenidentified. Farther from the cluster centre there is a gradual mergingbetween certain cluster members and field stars, both spatially andkinematically. Within the cluster, the kinematical structure is fullyconsistent with parallel space motion of the component stars with aninternal velocity dispersion of about 0.3 km s(-1) . The spatialstructure and mass segregation are consistent with N-body simulationresults, without the need to invoke expansion, contraction, rotation, orother significant perturbations of the cluster. The quality of theindividual distance determinations permits the cluster zero-age mainsequence to be accurately modelled. The helium abundance for the clusteris determined to be Y =3D 0.26+/-0.02 which, combined with isochronemodelling including convective overshooting, yields a cluster age of625+/-50 Myr. The distance to the observed centre of mass (a conceptmeaningful only in the restricted context of the cluster memberscontained in the Hipparcos Catalogue) is 46.34+/-0.27 pc, correspondingto a distance modulus m-M=3D3.33+/-0.01 mag for the objects within 10 pcof the cluster centre (roughly corresponding to the tidal radius). Thisdistance modulus is close to, but significantly better determined than,that derived from recent high-precision radial velocity studies,somewhat larger than that indicated by recent ground-based trigonometricparallax determinations, and smaller than those found from recentstudies of the cluster convergent point. These discrepancies areinvestigated and explained. } Based on observations made with the ESAHipparcos astrometry satellite. Table~2 is also available in electronicform at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)or via http://cdsweb.u-strasbg.fr/Abstract.html
| The dynamical properties of stellar systems in the Galactic disc
We postulate that stars in the Galactic field are born in aggregates ofbinary stars with half-mass radii R_0.5 and number of binaries N_binwhich are dynamically equivalent to the dominant-mode cluster (N_bin,R_0.5)~=(200, 0.8 pc). Binary orbits are distributed according to aninitial period distribution, which is consistent with pre-main-sequencedata. Stellar masses are paired at random from the KTG(1.3) massfunction. We develop a simple model for the redistribution or orbitalangular momentum and energy in short-period protobinary systems(pre-main-sequence eigenevolution), which establishes the observedcorrelations between eccentricity, mass ratio and period. The evolutionof orbital parameters owing to perturbations by neighbouring systems(stimulated evolution) within the dominant-mode cluster places 1-2 percent of all orbits into the eigenvolution region(P<100 d, e<~0.1approximately) of the eccentricity-period diagram. The number of suchforbidden orbits at any time is a function of the stellar numberdensity, the dynamical and the nuclear age of the cluster. Observationsof binaries in clusters should reveal the odd binary with forbiddenorbital parameters. Examples of such systems may be thepre-main-sequence binaries P2486 and EK Cep, and binaries in stellarclusters with eccentric orbits at periods smaller than thecircularization cut-off period. Eigenevolution is expected to depopulatethe eigenevolution region within 10^5 yr for pre-main-sequence binaries,but main-sequence binaries with forbidden orbits should remain in theeigenevolution region for times of order 10^9 yr. We show that thebinary star population must have a birth eccentricity distribution thatis approximately dynamically relaxed because stimulated evolution in thedominant-mode cluster cannot sufficiently thermalize a significantlydifferent distribution. After disintegration of the dominant-modecluster we have a population of Galactic field systems with orbitalparameters as observed, with a surviving proportion of binaries off_tot=0.48+/-0.03 which compares favourably with the observed proportionf^obstot=0.47+/-0.05. The rise of the period distribution to a maximumat log_10P~=4.8 reflects approximately the initial distribution, whereasthe decay for log_10P<~4.8 results fromstimulated evolution. The mass-ratio distribution of G dwarf binaries isdepleted at small mass ratios, and has the shape of the main-sequencedistribution, despite initially being the KTG(1.3) mass function. Wepredict and tabulate the mass-ratio distribution for main-sequencebinaries with a primary star less massive than 1.1 M_solar. Our modelGalactic field stellar population has a binary proportion among G, K andM dwarfs in good agreement with the observational data. Too few tripleand quadruple systems form by capture to account for the number ofobserved systems. An example of a triple system that may have formed bycapture in the birth aggregate may be Proxima Cen-alpha Cen A/B. Wecompare the specific angular momentum distribution of our initial binarystar population with the observed distribution of specific angularmomenta of molecular cloud cores. According to our model about 40 percent of all late-type stars are single after cluster dissolution, buthad companions with log_10P>~6 at birth. These stars are expected tohave circumstellar discs (and possible planetary systems) extending toat least about 40 au.
| 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.
| Evolved GK stars near the sun. I - The old disk population
A sample of nearly two thousand GK giants with intermediate band, (R,I),DDO and Geneva photometry has been assembled. Astrometric data is alsoavailable for most of the stars. The some 800 members of the old diskpopulation in the sample yield accurate luminosities (from two sources),reddening values and chemical abundances from calibrations of thephotometric parameters. Less than one percent of the objects arepeculiar in the sense that the flux distribution is abnormal. Thepeculiarity is signaled by strong CH (and Ba II) and weak CH. The CH+stars are all spectroscopic binaries, probably with white dwarfcompanions, whereas the CH- stars are not. A broad absorption band,centered near 3500 A, is found in the CH+ stars whereas the CH- objectshave a broad emission feature in the same region. The intensity of theseabsorptions and emissions are independent of the intensity of abnormalspectral features. Ten percent of the old disk sample have a heavyelement abundance from one and a half to three times the solar value.The distribution of the heavy element abundances is nearly a normal onewith a peak near solar abundance and ranges three times to one sixthsolar. The distribution of the (U, V) velocities is independent of theheavy element abundance and does not appear to be random. Ten percent ofthe old disk stars show a CN anomaly, equally divided between CN strongand CN weak. Several stars of individual astrometric or astrophysicalimportance are isolated.
| 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
| A critical appraisal of published values of (Fe/H) for K II-IV stars
'Primary' (Fe/H) averages are presented for 373 evolved K stars ofluminosity classes II-IV and (Fe/H) values beween -0.9 and +0.21 dex.The data define a 'consensus' zero point with a precision of + or -0.018 dex and have rms errors per datum which are typically 0.08-0.16dex. The primary data base makes recalibration possible for the large(Fe/H) catalogs of Hansen and Kjaergaard (1971) and Brown et al. (1989).A set of (Fe/H) standard stars and a new DDO calibration are given whichhave rms of 0.07 dex or less for the standard star data. For normal Kgiants, CN-based values of (Fe/H) turn out to be more precise than manyhigh-dispersion results. Some zero-point errors in the latter are alsofound and new examples of continuum-placement problems appear. Thushigh-dispersion results are not invariably superior to photometricmetallicities. A review of high-dispersion and related work onsupermetallicity in K III-IV star is also given.
| Lunar occultation and near-infrared speckle observations of DG Tauri, FV Tauri, FW Tauri and GG Tauri
Results are presented of near-infrared lunar occultation observations at2.2 microns. It is demonstrated that DG Tau has a 'shell' with adiameter of 6.8 AU (FWHM). A 1D projected image of this circumstellarstructure is reconstructed. Follow-up near-infrared speckle observationsshow a halo with a diameter of 130 AU, which is probably the outwardextension of the inner 'shell'. Our speckle measurements also show bothGG Tau and its nearby companion GG Tau/c to be double, possibly forminga hierarchical quadruple system. The duplicity of FV Tau and FW Taufound in previous lunar occultation observations by Chen et al. (1990)is confirmed. The projected positions of the companions of FV Tau and FWTau are determined. No duplicity or extended components were detected inthe cases of DL Tau, GU Tau, and IRAS 04212 + 2610.
| Seeing diagnosis for calibration in speckle interferometry
A new speckle interferometric tool is presented for seeing diagnosis andimproved seeing calibration. It provides a new seeing criterion. Thecomparability of the seeing conditions for object and reference star canbe ascertained in a more reliable manner than by the spectral ratiotechnique. The results shown refer to one-dimensional near-infraredspeckle scans which have been observed with the 3.5-m telescope on CalarAlto.
| XZ Tau resolved as double infrared source
Near-infrared speckel observations show the premain sequence star XZ Tauto be double with a separation of 0.30 arcmin + or - 0.02 arcmin at P.A.154 deg + or - 3 deg corresponding to 48 AU. While both components areequally bright at 1.2 microns, most of the near-infrared radiationlongward of 1.2 microns arises from the very red northern component.Neither of the two components were found to be extended and it is shownthat both of them are of stellar nature. It is suggested that thesouthern component coincides with the visible star and that the northernone constitutes an infrared companion which is more luminous than theoptical component.
| Large and kinematically unbiased samples of G- and K-type stars. IV - Evolved stars of the old disk population
Modified Stromgren and (R,I) photometry, along with DDO and Genevaphotometry, are presented for a complete sample of evolved old-disk Gand K giants in the Bright Star Catalogue. Stars with ages of between1.5 x 10 to the 9th and 10 to the 10th yr are found to have anear-normal distribution of heavy element abundances, centered on anFe/H abundance ratio of -0.1 dex. The old disk clusters NGC 3680 and IC4651 contain red-straggler young-disk giants that are probablycontemporaries of the blue stragglers in the clusters.
| Large and kinematically unbiased samples of G- and K-type stars. II - Observations of evolved stars in the Bright Star sample. III - Evolved young disk stars in the Bright Star sample
Four color and RI observations were obtained for a large sample ofG-type and K-type stars in the Bright Star Catalogue. Data are firstpresented for 110 evolved stars. Photometry of evolved young diskpopulation stars have then been calibrated for luminosity, reddening,and metallicity on the basis of results for members of the Hyades andSirius superclusters. New DDO results are given for 120 stars.
| A search for lithium-rich giant stars
Lithium abundances or upper limits have been determined for 644 brightG-K giant stars selected from the DDO photometric catalog. Two of thesegiants possess surface lithium abundances approaching the 'cosmic' valueof the interstellar medium and young main-sequence stars, and eight moregiants have Li contents far in excess of standard predictions. At leastsome of these Li-rich giants are shown to be evolved to the stage ofhaving convectively mixed envelopes, either from the direct evidence oflow surface carbon isotope ratios, or from the indirect evidence oftheir H-R diagram positions. Suggestions are given for the uniqueconditions that might have allowed these stars to produce or accrete newlithium for their surface layers, or simply to preserve from destructiontheir initial lithium contents. The lithium abundance of the remainingstars demonstrates that giants only very rarely meet the expectations ofstandard first dredge-up theories; the average extra Li destructionrequired is about 1.5 dex. The evolutionary states of these giants andtheir average masses are discussed briefly, and the Li distribution ofthe giants is compared to predictions of Galactic chemical evolution.
| Determining the temperatures of solar-type stars - Do star spots produce color anomalies?
The available evidence pertaining to color 'anomalies' in Hyades dwarfsare examined in detail in order to understand how the determine thetemperatures of solar-type stars. The evidence indicates that thetemperatures of these stars are not seriously skewed by their spots.Simpler explanations which can produce the observed effects arediscussed.
| A radial-velocity survey of the Hyades
Photoelectric radial-velocity measurements, obtained with external erroras small as 0.1 km/s using the 200-inch Hale telescope at PalomarObservatory during the period 1971-1986, are reported for over 400candidate members (with V magnitude between 6 and 14) of the Hyadescluster. The history of Hyades observations is recalled; the Palomarinstrumentation and observing program are described; the data-reductionand standardization procedures are discussed in detail; and the data arepresented in extensive tables and graphs. About 200 of the stars areclassified as cluster members, including 60 spectroscopic binaries.
| Spectroscopic binaries - 15th complementary catalog
Published observational data on the orbital characteristics of 436spectroscopic binaries, covering the period 1982-1986, are compiled intables. The data sources and the organization of the catalog are brieflydiscussed, and notes are provided for each item.
| Transformation equations and other aids for VRI photometry
Transformations among VRI systems are commonly beset by Paschen-jumpeffects, for which fully satisfactory allowance has not previously beenmade. This paper describes two new techniques which are based on thework of Gutierrez-Moreno, and which allow fully for the effects of thePaschen jump. Values of E(V-R)/E(B-V) and E(R-I)/E(B-V) are also givenfor the Cousins system for a wide range of temperatures. These and thenew techniques contribute to a set of new transformation relations whichapply for most VRI systems; the status of the remaining systems isreviewed, and future work needed for them is described. Two majorsources of Cousins VRI data underlie the new relations; the consistencyof these sources is reviewed and found to be generally satisfactory,although more work on this question is needed. Finally, three tables oftransformed standard-star and other data are given for the Cousins andJohnson systems, and a description of ways to reproduce the latter ispresented.
| Spectroscopic orbits for 16 more binaries in the Hyades field
A photoelectric survey of the radial velocities of Hyades candidates hasprovided data for 16 spectroscopic binary orbits, in addition to the 11known binaries in the Hyades field. The majority of photoelectricobservations in the survey were carried out at the Cambridge and PalomarObservatories using different data reduction techniques for determiningradial velocities. It is found that two of the objects, vB 164 and J336,are definitely not members of the Hyades cluster; two other objects, HD16909 and J301, appear to be located far from the center of the cluster,but still deserve classification as Hyades members. The gamma-velocityof HD 16909 differed slightly from the value expected for a member ofthe Hyades cluster. An additional twelve systems were definitelyidentified as members of the Hyades. The radial velocity values for allthe candidate stars are given in a series of tables.
| Photoelectric observations of lunar occultations. XIII
Occultation observations made with the 0.76 m reflector at McDonaldObservatory are presented, for 319 events occurring between Jan. 15,1981 and Feb. 7, 1982. One table reports timings, and a second recordsobservations of 16 double stars, in particular, Nu Gem observationsreveal that the two close components are similar in color. This allowsan estimation of individual visible magnitudes (near 4.60 and 5.32)suggesting that the secondary is a late B-type main-sequence star. SAO158929 observations reveal systematic differences in angular diametervalues. Of the 16 observed double stars, 9 appear to be new discoveries,including SAO 93067, SAO 94595, and SAO 98770. A third table gives fullydarkened angular diameters for the stars SAO 158929, SAO 77516 Y Tau,and SAO 119035 Nu Vir.
| Observational studies of Cepheids. I - BVRI photometry of bright Cepheids
Over 1,000 differentially determined photoelectric BVRI observations andthe resulting light curves are presented for 24 bright Cepheidsaccessible from Northern Hemisphere observatories. The internalprecision of these data is shown to be better than + or - 0.01 mag, andthe accuracy of transformation to the Johnson BVRI system is nearly asgood.
| Catalogue of stars with CaII H and K emissions
Not Available
| A set of faint equatorial standard stars for BVRI photometry
BVRI photoelectric photometry is presented for 48 of Landolt's (1973)faint equatorial standard stars. The 48 stars, which have spectral typesfrom A to K and V magnitudes in the range from 8.0 to 12.0, are chosento provide two blue and two red stars in each of 12 of the equatorialselected areas studied by Landolt. The program stars were observed withan S-1 photomultiplier, with the B-V, V-R, and V-I colors transformed tothe Johnson system; they were also observed with an RCA 31034Aphotomultiplier, with the resulting V-R and V-I colors given on azero-point-adjusted instrumental system. Observations of several Mdwarfs with the two photomultipliers are also reported. Serious problemsencountered in transforming the observed V-R and V-I colors of the Mdwarfs to the Johnson system are discussed.
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Pozíciós és asztrometriai adatok
| Csillagkép: | Bika |
| Rektaszcenzió: | 04h46m16.80s |
| Deklináció: | +18°44'06.0" |
| Vizuális fényesség: | 6.01 |
| Távolság: | 92.507 parszek |
| RA sajátmozgás: | 73.9 |
| Dec sajátmozgás: | -71.5 |
| B-T magnitude: | 7.558 |
| V-T magnitude: | 6.118 |
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