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# HD 94481

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 Precise radial velocities of giant stars. I. Stable starsContext: .Future astrometric missions such as SIM PlanetQuest need verystable reference stars. K giants have large luminosities, which placethem at large distances and thus the jitter of their photocenters bycompanions is relatively small. Therefore K giants would be best suitedas references. To confirm this observationally a radial velocity surveyis performed to quantify the level of intrinsic variability in Kgiants. Aims: .From this radial velocity survey we present 34 Kgiants with an observed standard deviation of the radial velocity ofless than 20 m/s. These stars are considered "stable" and can be used asradial velocity standards. Methods: .The radial velocity surveycontains 179 K giants. All K giants have a declination between -30°and +65° and visual magnitude of 3{-}6 mag. The CoudéAuxiliary Telescope (CAT) at UCO/Lick Observatory is used to obtainradial velocities with an accuracy of 5{-}8 m/s. The number of epochsfor the 34 stable stars ranges from 11 to 28 with a total timespan ofthe observations between 1800 and a little over 2200 days. Results: .The observational results of the 34 "stable" stars are showntogether with a discussion about their position in the MV vs.B-V diagram and some conclusions concerning the radial velocityvariability of K giants. These results are in agreement with thetheoretical predictions. K giants in a certain range of theMV vs. B-V diagram are suitable reference stars. A near-infrared stellar spectral library: I. H-band spectra.This paper presents the H band near-infrared (NIR) spectral library of135 solar type stars covering spectral types O5-M3 and luminosityclasses I-V as per MK classification. The observations were carried outwith 1.2 meter Gurushikhar Infrared Telescope (GIRT), at Mt. Abu, Indiausing a NICMOS3 HgCdTe 256 x 256 NIR array based spectrometer. Thespectra have a moderate resolution of 1000 (about 16 A) at the H bandand have been continuum shape corrected to their respective effectivetemperatures. This library and the remaining ones in J and K bands oncereleased will serve as an important database for stellar populationsynthesis and other applications in conjunction with the newly formedlarge optical coude feed stellar spectral library of Valdes et al.(2004). The complete H-Band library is available online at: http://vo.iucaa.ernet.in/~voi/NIR_Header.html Post-T Tauri Stars in the Nearest OB AssociationWe present results of a spectroscopic survey of X-ray- andproper-motion-selected samples of late-type stars in the LowerCentaurus-Crux (LCC) and Upper Centaurus-Lupus (UCL) subgroups of thenearest OB association: Scorpius-Centaurus. The primary goals of thesurvey are to determine the star formation history of the OB subgroupsand to assess the frequency of accreting stars in a sample dominated bypost-T Tauri'' pre-main-sequence (PMS) stars. We investigate twosamples: (1) proper-motion candidates from the ACT Catalog and TychoReference Catalog (TRC) with X-ray counterparts in the ROSAT All-SkySurvey (RASS) Bright Source Catalog and (2) G- and K-type stars in theHipparcos catalog found to be candidate members by de Zeeuw et al. Weobtained optical spectra of 130 candidates with the Siding Spring 2.3 mdual-beam spectrograph. PMS stars were identified by (1) strong Liλ6707 absorption, (2) subgiant surface gravities, (3) propermotions consistent with Sco-Cen membership, and (4) H-R diagrampositions consistent with being PMS. We find 93% of the RASS-ACT/TRCstars to be probable PMS members, compared with 73% of the Hipparcoscandidates. We demonstrate that measuring the gravity-sensitive bandratio of Sr II λ4077 to Fe I λ4071 is a valuable means ofdiscriminating PMS and zero-age main-sequence (ZAMS) stars. Usingsecular parallaxes and Hipparcos, Tycho-2, and Two Micron All Sky Surveyphotometry, we construct an H-R diagram. Depending on the choice ofpublished evolutionary tracks, we find the mean ages of the PMSpopulations to range between 17 and 23 Myr for LCC and 15 and 22 Myr forUCL. Taking into account observational errors, it appears that 95% ofthe low-mass star formation in each subgroup must have occurred in lessthan 8 Myr (LCC) and 12 Myr (UCL). Using the Bertelli et al. tracks, wefind main-sequence turnoff ages for Hipparcos B-type members to be16+/-1 Myr for LCC and 17+/-1 Myr for UCL. Contrary to previousfindings, it appears that LCC is coeval with, or slightly older than,UCL. The secular parallaxes of the Sco-Cen PMS stars yield distances of85-215 pc, with 12 of the LCC members lying within 100 pc of the Sun.Only one out of 110 (0.9+2.1-0.8%; 1 σ) PMSsolar-type stars in the sample with ages of 13+/-1 (s.e.)+/-6 (1σ) Myr and masses of 1.3+/-0.2 (1 σ) Msolar showsboth enhanced Hα emission and a K-band excess indicative ofaccretion from a truncated circumstellar disk: the nearby (d~=86 pc)classical T Tauri star PDS 66. A Strategy for Identifying the Grid Stars for the Space Interferometry MissionWe present a strategy to identify several thousand stars that areastrometrically stable at the microarcsecond level for use in the SpaceInterferometry Mission (SIM) astrometric grid. The requirements on thegrid stars make this a rather challenging task. Taking a variety ofconsiderations into account, we argue for K giants as the best type ofstars for the grid, mainly because they can be located at much largerdistances than any other type of star owing to their intrinsicbrightness. We show that it is possible to identify suitable candidategrid K giants from existing astrometric catalogs. However, double starshave to be eliminated from these candidate grid samples, since theygenerally produce much larger astrometric jitter than tolerable for thegrid. The most efficient way to achieve this is probably by means of aradial velocity survey. To demonstrate the feasibility of this approach,we repeatedly measured the radial velocities for a preselected sample of86 nearby Hipparcos K giants with precisions of 5-8 m s-1.The distribution of the intrinsic radial velocity variations for thebona fide single K giants shows a maximum around 20 m s-1,which is small enough not to severely affect the identification ofstellar companions around other K giants. We use the results of ourobservations as input parameters for Monte Carlo simulations on thepossible design of a radial velocity survey of all grid stars. Ourfavored scenario would result in a grid which consists to 68% of truesingle stars and to 32% of double or multiple stars with periods mostlylarger than 200 years, but only 3.6% of all grid stars would displayastrometric jitter larger than 1 μas. This contamination level isprobably tolerable. The properties of field elliptical galaxies at intermediate redshift - II. Photometry and spectroscopy of an HST-selected sampleA sample of field early-type galaxies (E/S0) at intermediate redshift(z~0.1-0.6) is selected, based on morphology and colours from HST-WFPC2parallel images. Photometric structural parameters (effective radiusRe and effective surface brightness SBe) arederived through the F606W and F814W filters, using luminosity profilefitting and two-dimensional fitting techniques. The combined parameterthat enters the Fundamental Plane(logRe-βSBe, with β~0.32) is shown tosuffer from significantly smaller uncertainties (rms 0.03) than theindividual structural parameters (e.g. ~15 per cent rms on the effectiveradius). High signal-to-noise ratio, intermediate-resolution spectra,taken at the ESO 3.6-m telescope, yield redshifts for 35 galaxies andcentral velocity dispersions for 22 galaxies. Central velocitydispersions are derived using a library of stellar templates covering awide range of spectral types, in order to study the effects of templatemismatches. The average random error on the central velocity dispersionis found to be 8 per cent, and the average systematic error caused bytemplate mismatch is found to be 5 per cent. The errors in the velocitydispersion measurement and the effects of template mismatches arestudied by means of extensive Monte Carlo simulations. In addition, weinvestigate whether the determination of the velocity dispersion issensitive to the spectral range used, finding that the value of velocitydispersion is unchanged when the spectral regions that include theabsorption features Ca H and K and NaD are masked out during the fit. Speckle Observations of Composite Star CandidatesSpeckle observations are reported for 53 stars with composite spectraselected from the Michigan Spectral Catalogue in an effort to improvethe orbits of known binaries and to discover new binaries among thisclass of objects. The data were obtained using the 1.3 and 2.4 mtelescopes at the Michigan-Dartmouth-MIT Observatory and the GeorgiaTech Research Institute speckle imaging system. For 50 stars in thesample for which no indication of duplicity was found in our data, wemay place an upper limit of <=0.2" on the separations at the epochsof observation. Three stars were resolved, including HD 26796, alsodiscovered to be double by Hipparcos. A discussion of the accuracy ofthe measurements based on comparisons with speckle standard stars ispresented. Sixth Catalogue of Fundamental Stars (FK6). Part III. Additional fundamental stars with direct solutionsThe FK6 is a suitable combination of the results of the HIPPARCOSastrometry satellite with ground-based data, measured over a longinterval of time and summarized mainly in the FK5. Part III of the FK6(abbreviated FK6(III)) contains additional fundamental stars with directsolutions. Such direct solutions are appropriate for single stars or forobjects which can be treated like single stars. Part III of the FK6contains in total 3272 stars. Their ground-based data stem from thebright extension of the FK5 (735 stars), from the catalogue of remainingSup stars (RSup, 732 stars), and from the faint extension of the FK5(1805 stars). From the 3272 stars in Part III, we have selected 1928objects as "astrometrically excellent stars", since their instantaneousproper motions and their mean (time-averaged) ones do not differsignificantly. Hence most of the astrometrically excellent stars arewell-behaving "single-star candidates" with good astrometric data. Thesestars are most suited for high-precision astrometry. On the other hand,354 of the stars in Part III are Δμ binaries in the sense ofWielen et al. (1999). Many of them are newly discovered probablebinaries with no other hitherto known indication of binarity. The FK6gives, besides the classical "single-star mode" solutions (SI mode),other solutions which take into account the fact that hidden astrometricbinaries among "apparently single-stars" introduce sizable "cosmicerrors" into the quasi-instantaneously measured HIPPARCOS proper motionsand positions. The FK6 gives, in addition to the SI mode, the "long-termprediction (LTP) mode" and the "short-term prediction (STP) mode". TheseLTP and STP modes are on average the most precise solutions forapparently single stars, depending on the epoch difference with respectto the HIPPARCOS epoch of about 1991. The typical mean error of anFK6(III) proper motion in the single-star mode is 0.59 mas/year. This isa factor of 1.34 better than the typical HIPPARCOS errors for thesestars of 0.79 mas/year. In the long-term prediction mode, in whichcosmic errors are taken into account, the FK6(III) proper motions have atypical mean error of 0.93 mas/year, which is by a factor of about 2better than the corresponding error for the HIPPARCOS values of 1.83mas/year (cosmic errors included). Ca II activity and rotation in F-K evolved starsCa II H and K high resolution observations for 60 evolved stars in thefield and in 5 open clusters are presented. From these spectrachromospheric fluxes are derived, and a homogeneous sample of more than100 giants is built adding data from the literature. In addition, formost stars, rotational velocities were derived from CORAVELobservations. By comparing chromospheric emission in the cluster starswe confirm the results of Pasquini & Brocato (1992): chromosphericactivity depends on the stellar effective temperature, and mass, whenintermediate mass stars (M ~ 4 Msun) are considered. TheHyades and the Praesepe clump giants show the same level of activity, asexpected from stars with similar masses and effective temperatures. Adifference of up to 0.4 dex in the chromospheric fluxes among the Hyadesgiants is recorded and this sets a clear limit to the intrinsic spreadof stellar activity in evolved giants. These differences in otherwisevery similar stars are likely due to stellar cycles and/or differencesin the stellar initial angular momentum. Among the field stars none ofthe giants with (V-R)o < 0.4 and Ia supergiants observedshows a signature of Ca II activity; this can be due either to the realabsence of a chromosphere, but also to other causes which preclude theappearance of Ca II reversal. By analyzing the whole sample we find thatchromospheric activity scales linearly with stellar rotational velocityand a high power of stellar effective temperature: F'k ~Teff7.7 (Vsini)0.9. This result can beinterpreted as the effect of two chromospheric components of differentnature: one mechanical and one magnetic. Alternatively, by using theHipparcos parallaxes and evolutionary tracks, we divide the sampleaccording to the stellar masses, and we follow the objects along anevolutionary track. For each range of masses activity can simply beexpressed as a function of only one parameter: either theTeff or the angular rotation Omega , with laws F'k~ Omega alpha , because angular velocity decreases witheffective temperature along an evolutionary track. By using theevolutionary tracks and the observed Vsini we investigate the evolutionof the angular momentum for evolved stars in the range 1-5Msun. For the 1.6-3 solar mass stars the data are consistentwith the IOmega =const law while lower and higher masses follow a lawsimilar to IOmega 2=const, where I is the computed stellarmomentum of inertia. We find it intriguing that Vsini remains almostconstant for 1Msun stars along their evolution; if a similarbehavior is shared by Pop II stars, this could explain the relativelyhigh degree of activity observed in Pop II giants. Finally, through theuse of models, we have verified the consistency of the F'k ~Omega alpha and the IOmega beta = Const lawsderived, finding an excellent agreement. This representation, albeitcrude (the models do not consider, for instance, mass losses) representsthe evolution of Ca II activity and of the angular momentum in asatisfactory way in most of the portion of HR diagram analyzed.Different predictions could be tested with observations in selectedclusters. Based on observations collected at ESO, La Silla. Tables 1-3are only available in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html A catalog of rotational and radial velocities for evolved starsRotational 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 Rotational Velocities of Late-Type StarsA 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) Medium-Resolution Spectra of Normal Stars in the K BandAn Atlas of 115 medium-resolution K-band (2.0--2.4 mu m) stellarspectra, spanning spectral types O--M and luminosity types I--V, ispresented. K-band spectra are also presented for one N- and one J-typecarbon star. A time series of spectra is presented for an S-type Miravariable. All the spectra are at a resolution of ~3000 (1.4 cm-1) andhave had the terrestrial absorption removed by dividing by a featurelessspectrum. The spectra are plotted with the major spectral featuresidentified and are available digitally. Doppler imaging of stellar surface structure. IV. The rapidly-rotating G5III-IV star HD 112313 = IN Comae.We present the first Doppler image of the rapidly-rotating G5 giant inthe unusual IN Comae triple system. Our average image from threespectral regions and two continuum color indices shows mostly low tohigh latitude features but not a prominent polar cap-like spot. Aparameter study of the stellar and atomic input quantities aims tobetter quantify the reliability of our Doppler image. A time series of330 high-precision Stroemgren by and Johnson V measurements in 1996 showonly one real photometric period (5.913+/-0.005days) that we interpretto be the rotation period of the G5 giant. We found no evidence for the0.25-day period claimed earlier by Kuczawska & Mikolajewski(1993AcA....43..445K). Optical spectra of several activity indicatorsare presented and discussed. IN Comae exhibits an unusual broad Hαemission line and a central absorption feature. This profile shape isalso seen for the CaII infrared-triplet lines as well as for the sodiumdoublet and the HeI D_3_ line. No LiI 6707.8 line is present. New radialvelocity measurements from our red-wavelength spectra do not indicate ashort-period binary but would be consistent with the G5 star being theouter, third component of this triple system. 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 position corrections of 1400 stars observed with PA II in San Juan.Not Available Spectral classifications in the near infrared of stars with composite spectra. I. The study of MK standards.Up to now the spectral classifications of the cool components ofcomposite spectra obtained in the 3800-4800A wavelength region have beenvery disparate. These disparities are due to the fact that the spectraof the evolved cool component are strongly veiled by that of the hotterdwarf component, which makes a classification very difficult. We proposeto study these systems in the near infrared (8380-8780A). In thisspectral domain the magnitude difference between the spectra of thecomponents is in general sufficiently large so that one observespractically only the spectrum of the cool component. In this first paperwe provide, for a sample of MK standards, the relations between theequivalent width (Wlambda_ ) of certain lines and thespectral classifications. For the cool G, K and M type stars, the linesconsidered are those of the calcium triplet (Ca II 8498, 8542 and 8662),of iron (Fe I 8621 and 8688), of titanium (Ti I 8426 and 8435) and ofthe blend λ8468. The use of certain line intensity ratiospermits, after eliminating partially the luminosity effects, a firstapproach to the spectral type. For the hotter stars of types O, B, A andF we study the behavior of the hydrogen lines (P12 and P14), the calciumlines (Ca II 8498 and 8542) as well as those of the oxygen (O I 8446).The latter line presents a very characteristic profile for stars of lowrotation and therefore in Am stars, which are frequently found among thecomposite spectrum binaries. Among the cooler stars of our sample, only6% present real anomalies with respect to the MK classifications. Thisresult is very encouraging for undertaking the classification of asample of composite spectra. The spectra were taken at the Observatoirede Haute-Provence (OHP) with the CARELEC spectrograph at the 193 cmtelescope, with a dispersion of 33 A/mm. Chromospheric Activity in Galactic Open ClustersAbstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993ApJ...417..157B&db_key=AST Fifth fundamental catalogue. Part 2: The FK5 extension - new fundamental starsThe mean positions and proper motions for 3117 new fundamental starsessentially in the magnitude range about 4.5 to 9.5 are given in thisFK5 extension. Mean apparent visual magnitude is 7.2 and is on average2.5 magnitudes fainter then the basic FK5 which has a mean magnitude of4.7. (The basic FK5 gives the mean positions and proper motions for theclassical 1535 fundamental stars). The following are discussed: theobservational material, reduction of observations, star selection, andthe system for the FK5 extension. An explanation and description of thecatalog are given. The catalog of 3117 fundamental stars for the equinoxand epoch J2000.0 and B1950.0 is presented. The parallaxes and radialvelocities for 22 extension stars with large forecasting effects aregiven. Catalogs used in the compilation of the FK5 fundamental catalogare listed. Large and Kinematically Unbiased Samples of G- and K-Type Stars. III. Evolved Young Disk Stars in the Bright Star SampleAbstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1989PASP..101...54E&db_key=AST 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 sampleFour 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 list of MK standard starsNot Available The Perkins catalog of revised MK types for the cooler starsA catalog is presented listing the spectral types of the G, K, M, and Sstars that have been classified at the Perkins Observatory in therevised MK system. Extensive comparisons have been made to ensureconsistency between the MK spectral types of stars in the Northern andSouthern Hemispheres. Different classification spectrograms have beengradually improved in spite of some inherent limitations. In thecatalog, the full subclasses used are the following: G0, G5, G8, K0, K1,K2, K3, K4, K5, M0, M1, M2, M3, M4, M5, M6, M7, and M8. Theirregularities are the price paid for keeping the general scheme of theoriginal Henry Draper classification. The rotational break for G giantsNew high-resolution spectroscopic observations have been obtained for 73G giants. Fourier analysis of their spectral lines yields rotationvelocities and macroturbulence dispersions. Combined with data from anearlier study, total of 86 analyses of luminosity class III giants isnow available. The existence of a rotational discontinuity forluminosity class III giants is confirmed, but it is found to be near G0III rather than G5 III, as indicated in the earlier work. Evidence forrotation being a single-valued function of spectral type isstrengthened. The observations are interpreted in terms of adynamo-generated magnetic brake and a 'rotostat' phenomenon. 1988 Revised MK Spectral Standards for Stars GO and LaterNot Available 1985 revised MK spectral standards : stars GO and laterNot Available Revised MK Spectral Standard Stars Later than G0Not Available Uvby-Beta Photometry of Equatorial and Southern Bright Stars - Part TwoAbstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&AS...42..311H&db_key=AST Estimation of spectral classifications for bright southern stars with interesting Stromgren indicesThis paper investigates the degree of success with which uvby photometrycan be applied to predict spectral classifications for 947 A, F, and Gstars brighter than an apparent magnitude of 8.3 and with four-colorindices indicating some kind of interesting, unusual, or peculiarspectrum. One or several possible spectral classifications are estimatedfor each star from photometry alone, double stars are distinguished, andthe estimates are compared with published classifications. The resultsshow that the framework provided by uvby photometry can be extended toinclude most G and K stars, reddened stars, peculiar stars, and certaintypes of double star. Catalog of Indidual Radial Velocities, 0h-12h, Measured by Astronomers of the Mount Wilson ObservatoryAbstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970ApJS...19..387A&db_key=AST
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