The Kinematics of Thick Disks in External Galaxies
We present kinematic measurements of the thick and thin disks in twoedge-on galaxies. We have derived stellar rotation curves at and abovethe galaxies' midplanes using Ca II triplet features measured with theGMOS spectrograph on Gemini North. In one galaxy, FGC 1415, thekinematics above the plane shows clear rotation that lags that of themidplane by ~20%-50%, similar to the behavior seen in the Milky Way.However, the kinematics of the second galaxy, FGC 227, is quitedifferent. The rotation above the plane is extremely slow, showing<~25% of the rotation speed of the stars at the midplane. Wedecompose the observed rotation curves into a superposition of thick-and thin-disk kinematics, using two-dimensional fits to the galaxyimages to determine the fraction of thick-disk stars at each position.We find that the thick disk of FGC 1415 rotates at 30%-40% of therotation speed of the thin disk. In contrast, the thick disk of FGC 227is very likely counterrotating if it is rotating at all. Theseobservations are consistent with the velocity dispersion profiles thatwe measure for each galaxy. The detection of counterrotating thick disksconclusively rules out models in which the thick disk forms eitherduring monolithic collapse or from vertical heating of an earlier thindisk. Instead, the data strongly support models in which the thick diskforms from direct accretion of stars from infalling satellites.
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High-resolution Doppler images of the spotted contact binary AE Phe
We present Doppler images of the short period (P= 0.362 d) W UMa binaryAE Phe. In order to obtain the necessary S/N ratio and time resolutionrequired to see individual star-spot features in highly rotationallybroadened profiles, we use least-squares deconvolution, which makes useof the information content of the several thousand lines in a typicalechelle spectrum. This yields a single rotation profile (free ofsidelobes due to blending) per spectrum with a typical S/N ratio ofseveral thousand.We use radial velocity curves, generated from standard profile fittingtechniques, to measure velocity amplitudes and the mass ratio. Failureto model star-spots with this method leads to a biased set of values,and we show that an imaging code is essential if accurate systemparameters are to be derived.Images are reconstructed from four nights of data which revealstar-spots at most latitudes on both components of the common envelopesystem. Our model requires that the primary component be several hundredK cooler than the secondary in order to reproduce the profile depthchanges with phase. In a two-temperature imaging model, we interpretthis as being due to 27 per cent greater - but unresolved - spot fillingon the primary relative to the secondary component. The images revealthat dark spots are present on both stars at various latitudes andlongitudes. Star-spots are also found in the neck region of bothcomponents, which appear to be darker on the side of each star leadingin rotation phase - particularly on the secondary component. Weinvestigate the reproducibility of the images from night to night andconclude that the star-spots evolve significantly on very shorttime-scales, of the order of 1 d. This is significantly faster than theweek time-scales found on active single stars and the Sun.
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Doppler images from dual-site observations of southern rapidly rotating stars - II. Starspot patterns and differential rotation on Speedy Mic
We have secured high spatial and temporal resolution spectra of therapidly rotating K dwarf Speedy Mic (HD 197890) at two sites and acommon epoch of observations. The 0.38-d axial rotation period and theV-band magnitude of 9.33 make it a difficult target for Doppler imaging.In order to obtain high signal-to-noise ratio profiles from 300-sexposures, we apply the technique of least-squares deconvolution to thelarge number of photospheric absorption lines available in each of ourspectra. This allows us to derive high-resolutionmaximum-entropy-regularized Doppler images of the stellar surface. Usingthese techniques, we also derive radial velocities and accurateprojected equatorial rotation velocities which are consistent to within~1kms-1. Our surface maps reveal one of the most heavilyspotted photospheres seen on a rapid rotator, with starspots occurringat all latitudes. At the time of observations, Speedy Mic had no strongpolar spot, but it shows spots concentrated in low- andintermediate-latitude bands. We attempt a differential rotationmeasurement, but lack of sufficient phase coverage allows determinationof only a lower limit of 59d for the time it takes the equatorialregions to lap the polar regions. We also find variations in the heavilyfilled-in Hα line which can be attributed to prominences passingin front of the stellar disc. Despite the rapid rotation, the appearanceof the same features on consecutive nights of observations shows theclouds to be stable on time-scales of at least a day.
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CCD photometry and astrometry of visual double and multiple stars of the HIPPARCOS Catalogue. II. CCD photometry and differential astrometry of 288 southern ``Intermediate'' systems
We present photometric and astrometric data of about 280 visual doublestars of the ``intermediate'' class, i.e. with angular separationsmainly in the range 2arcsec < rho < 12arcsec . The observationshave been obtained in 1991-92 with a CCD camera attached to the 91 cmDutch telescope at ESO La Silla, Chile. Differential magnitudes of thedouble star components as well as magnitudes and colour indices of theindividual components have been determined in the Cousins V and Ipassbands with an internal error of about 0.005 mag and an externalaccuracy of less than 0.03 mag. In addition, angular separations havebeen secured to an internal accuracy of 0.004arcsec and position anglesto about 0.05degr. Tables 1 to 4 are only available in electronic format the CDS via ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html. Based on observationscollected at the European Southern Observatory, La Silla, Chile.
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Radial velocities. Measurements of 2800 B2-F5 stars for HIPPARCOS
Radial velocities have been determined for a sample of 2930 B2-F5 stars,95% observed by the Hipparcos satellite in the north hemisphere and 80%without reliable radial velocity up to now. Observations were obtainedat the Observatoire de Haute Provence with a dispersion of 80Ä,mm(-1) with the aim of studying stellar and galactic dynamics.Radial velocities have been measured by correlation with templates ofthe same spectral class. The mean obtained precision is 3.0 km s(-1)with three observations. A new MK spectral classification is estimatedfor all stars. Based on observations made at the Haute ProvenceObservatory, France and on data from The Hipparcos Catalogue, ESA.Tables 4, 5 and 6 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr or viahttp://cdsweb.u-strasbg.fr/Abstract.htm
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Lithium in the low-mass stars of the Coma Berenices open cluster
I report lithium abundances and radial velocities for 15 late F, G and Kstars in the Coma Berenices open cluster. All the stars are propermotion members, and the radial velocities enable us to confirmmembership for 11 single stars and identify three SB1 systems and oneshort-period SB2 system that are very probable cluster members. Thepattern of Li abundances is similar to that in the Hyades, with someevidence for higher Li abundances in Coma Ber for T_eff<5700 K. Iargue that these data do not support standard models for Li depletioninvolving only convective mixing, because the Coma Ber stars haveconsistently determined lower metallicities and shallower convectionzones than the Hyades and should have suffered a great deal less Lidepletion than observed. Instead, it seems that the Li abundances inthese and other young clusters are primarily ranked according to theirage rather than their metallicity. I propose a scenario where theextreme metallicity dependence of pre-main-sequence Li depletion istempered by a mechanism that severely inhibits convective mixing, wherecontinued main-sequence depletion occurs via non-standard mixingmechanisms, and where any dependence of Li depletion on metallicitytakes at least several hundred Myr to emerge.
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Membership and lithium abundances of late-type stars in NGC 6633
NGC 6633 is a young, open cluster with a similar age to the Hyades andPraesepe but lower metallicity. Using a new photometric survey andproper-motion information, a sample of candidate members of NGC 6633have been observed spectroscopically. Radial velocities are used toconfirm membership for 21 late-type stars including two spectroscopicbinaries. By combining the spectroscopy with existing UBV photometry, itis shown that NGC 6633 has a significantly lower metallicity than theHyades but not much lower than M/H = 0.0. The projected equatorialvelocities of the cluster members are compared with Hyades rotation dataand found to be consistent. The lithium abundances are indistinguishablefrom those in the Hyades for F stars but show a different pattern ofdepletion in the cooler stars that can be qualitatively attributed tothe lower metallicity. Comparison with younger Pleiades cool stars,which have a similar metallicity to NGC 6633, shows that Li depletionapparently occurs in G and K stars while they are on the main sequence.Standard models, incorporating only convective mixing, underpredict thedepletion in both the Hyades and NGC 6633, but match the lower envelopeof the Pleiades distribution. These data argue strongly against enhancedinterior opacities as a way of increasing Li depletion in the standardmodels, and instead point to extra mixing mechanisms on the mainsequence combined with a rotation-dependent Li depletion inhibitionprocess acting during pre-main-sequence evolution.
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Circumstellar Gas in the Wide Binary HD 188037
We report radio, optical, and ultraviolet studies of the wide binary HD188037 (=IRC +20439). We detect the CO (2--1) and (1--0) rotationallines from the circumstellar envelope in this system, which consists ofa luminous (~7000 Lȯ) mass-losing M-type star and, at a separationof 0."75, a main-sequence A-type star. The strong (2--1) line has a veryunusual skewed shape with a width at zero intensity of about 30 km s-1,which we explain with a model wherein the gas ejected by the M-type staris preferentially photodissociated on one side of the outflow byultraviolet light from the A-type companion. We infer that the wind fromthe M giant expands at 15 km s-1 and, for an estimated distance of 300pc, carries ~3 x 10-7 Mȯ yr-1. Our simplified model for CO in awind being photodissociated by ultraviolet from a companion explains whyCO can be detected around Mira yet not around alpha Sco.
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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.
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A preliminary compilation of DS-programme star positions
A catalog is presented of the double-star-program (DS-program) starpositions, listing right ascensions for 930 DSs and declinations for1225 DSs of the program. The positions were compiled from the observedvalues obtained between 1980 and 1987 with the meridian circles of sixUSSR observatories (the Moscow, Kazan', Kiev, Khar'kov, Odessa, andTashkent Observatories) and the Belgrade Observatory. The measurementsand the treatment of the observational material were performed using therelative method, and the FK-4 system stars were used as reference stars.
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Radial velocities of 26 northern Milky Way Cepheids
Spectra taken with the Palomar 60 inch echelle spectrograph are used toobtain 231 radial velocity measurements of 26 northern hemisphere MilkyWay Cepheids with latitude between 15 and 140 deg and b below 5 deg. Thetypical accuracy of the Cepheid velocities is 0.8 km/s. Radialvelocities of standard stars with accuracies of 0.6 km/s are alsoreported, and zero points determined from several systems are compared.The adopted zero point agrees with those of several other systems to +or - 0.1 km/s.
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Large and kinematically unbiased samples of G- and K-type stars. V - Evolved stars in the selected areas at + 15-deg declination
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990PASP..102..242E&db_key=AST
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A second list of wide visual binaries
Not Available
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A second list of wide visual binaries
Not Available
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Progress toward a multiobject radial-velocity spectrometer
It is shown that it is possible to obtain stellar radial velocities ofhigh accuracy using a fiber-fed echelle spectrograph with no crossdisperser. Although the resulting spectrum contains many overlappingorders, the radial-velocity information is still present. Velocities maybe obtained by cross correlation with reference data obtained with thesame instrument. The accuracy is a function of the signal-to-noiseratio, and ranges from + or - 4 km/s to + or - 1 km/s. Velocities areobtained with exposure times just sufficient to obtain the barest traceof a spectrum using the same spectrograph and CCD detector with a crossdisperser. Thus, it appears possible to obtain precision similar to thatobtained with an order separator, but with considerably bettersensitivity, due to a multiplexing gain. Moreover, the overlappingorders of the stellar spectrum only occupy a few rows of the CCD. Usinga multiple-fiber-feed device, many such spectra could be fit on the CCD.This leads to the expectation of obtaining many radial velocitiessimultaneously using a multiobject spectrometer now under constructionat Cerro Tololo.
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A radial velocity survey of extremely hydrogen-deficient stars
A radial velocity survey of hot extremely hydrogen-deficient starsconfirms HDE 320156 to be a single-lined spectroscopichydrogen-deficient binary. The three hydrogen-deficient stars detectedall show weak C-lines. Little evidence is found for the small-amplituderadial velocity variations known to be present among the extreme-helium(EHe) stars. The heliocentric radial velocity distributions andkinematics of the known EHe stars are found to be consistent with an oldstellar population which is strongly concentrated towards the Galacticcenter, and evidence suggests that the EHe stars are all single.
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Stellar radial-velocity meter
A photoelectric radial-velocity meter with an echelle spectrographoperating in a Cassegrain focus is described. The stars of spectraltypes later than F5 can be observed. The results of the observations of13 IAU standards are given. The rms difference of the measuredvelocities from the standard ones is 0.5 km/s and the reproducibility ofthe velocities of bright stars is about 0.25 km/s. The limitingmagnitude is approximately V = 10 m, and it will be improved in thefuture.
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An analysis of the radial-velocity performance of the image-tube spectrograph on the CTIO 1-meter telescope
An analysis of the radial-velocity performance of the 120 A/mmconfiguration of the image-tube spectrograph on the CTIO/Yale 1-metertelescope is presented. The instrument is found to be stable within agiven run but to be susceptible to small changes from run to run. Theremay be systematic changes in velocity residual with declination; noneare found with zenith angle or hour angle. A typical precision of plusor minus 10 km/sec for a single spectrum of a Population I star isachieved for the spectrograph configuration. Rest wavelengths derivedfor F0-K4 Population I stars observed with this spectrograph/image-tubeconfiguration are presented. A table of radial velocities and residualsfor IAU radial-velocity standard stars, as well as some other brightstars, is also presented.
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The zero-point of the 'Fick' radial-velocity stars
The radial velocities determined for 61 stars by Beavers et al. (1979)using the spectrometer developed at Fick Observatory are compared withthose derived from observations obtained using the coude-feedspectrograph at KPNO over the spectral range from F8 through K4 during1978-1981. The stellar effective wavelengths used in analyzing the KPNOobservations are established using observations of solar-system objects.The data are presented in tables, and the difference between the Fickand KPNO radial velocities is found to be 0.0 + or - 0.1 km/s, comparedto 0.4 + or - 0.5 km/s for a group of IAU standard objects also checkedat KPNO. These low differences confirm the accuracy of the Fick and IAUzero points.
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Standard Velocity Stars
Not Available
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Observations of Standard Velocity Stars
Not Available
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Radial velocities of IAU standard stars
Radial velocities of 52 IAU Radial Velocity Standard stars, obtainedfrom 358 spectra of 12 and 20 A/mm dispersion during the 1970-1978period, are presented. Some discrepancies between the present resultsand those of the IAU are discussed.
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Masses of red giants. I - Mean initial mass from visual binary data
Existing information on red-giant masses is reviewed, and an independentmethod for determining the frequency distribution of initial masses ofred giants is presented which is based on analysis of visual binarysystems containing a red giant and a main-sequence star (RG-MS systems).A list of RG-MS systems is compiled which yields an apparent frequencydistribution of the spectral types of the secondaries. This apparentdistribution is transformed to a 'true' distribution of secondary massesby accounting for certain selection effects; the true distribution isthen transformed into a distribution of initial primary masses (i.e.,initial masses of red-giant components) by assuming a form for thedistribution of mass ratios. Values in the range from 0.8 to 1.2 solarmasses and an upper limit of 1.4 solar masses are determined for themean initial masses of red giants and shown to be in satisfactoryagreement with the theoretical prediction of about 1 solar mass.
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The stellar aggregate surrounding HD 101205 (IC 2944).
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977A&A....54..233A&db_key=AST
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Liste de vitesses radiales mesurees AU spectrographe coude a fente dutelescope de 193 CM (dispersions de 40 et 19,5 A/mm).
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974A&AS...16..359F&db_key=AST
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Spectrographic and photometric observations of supergiants and foreground stars in the direction of the Large Magellanic Cloud
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972A&AS....6..249A&db_key=AST
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La mesure des vitesses radiales AU spectrographe coude DU telescope de 152 CM de l'Observatoire de Hte Provence.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972A&A....19..427F&db_key=AST
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Determination of atmospheric parameters for G and K giants by means of photoelectric indices.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971A&A....15..123H&db_key=AST
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Photoelectric radial velocities. IV. 528 7 to 10 mag stars in the +15degree selected areas.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971MNRAS.155....1G&db_key=AST
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Stellar radial velocities derived from microphotometer measurements.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1969AJ.....74...91L&db_key=AST
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INHABITED SKY
