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Fundamental properties of pre-main sequence stars in young, southern star forming regions: metallicities
Aims. The primary motivation for this project is to search formetal-rich star forming regions, in which, stars of super-solarmetallicity will be created, as hopefully, will be extra-solar planetsorbiting them! The two aims of this project are: 1) to show that oursample stars are young, lithium rich, magnetically active andnon-accreting kinematic members of their respective regions. 2) Tomeasure the metallicity for such members. Methods. The feroséchelle spectrograph together with eso's 2.2 m telescope, wasused to obtain high resolution (R = 32 000) spectra for each of ourweak-lined T-Tauri target stars. The wavelength range of the spectra is≃4000{-}8000 Å. Results. We find (pre-main sequence)model-dependent isochronal ages of the Lupus, Chamaeleon and CrA targetsto be 9.1 ± 2.1 Myr, 4.5 ± 1.6 Myr and 9.0 ± 3.9Myr respectively. The majority of the stars have Li i 6707.8 Åequivalent widths similar to, or above those of, their similar massPleiades counterparts, confirming their youthfulness. Most stars arekinematic members, either single or binary, of their regions. We find amean radial velocity for objects in the Lupus cloud to be RV=+2.6± 1.8 km s-1, for the Chamaeleon i & ii clouds,RV=+12.8 ± 3.6 km s-1 whereas for the CrA cloud, wefind RV=-1.1 ± 0.5 km s-1. All stars are coronally andchromospherically active, exhibiting X-ray and Hα emission levelsmarginally less, approximately equal or superior to that of their olderIC 2602/2391 and/or Pleiades counterparts. All bar three of the targetsshow little or no signature of accretion from a circumstellarenvironment, according to their positions in a J-K/H-K'diagram. For the higher quality spectra, we have performed an iron-linemetallicity analysis for five (5) stars in Chamaeleon, four (4) stars inLupus and three (3) stars in the CrA star forming regions. These resultsshow that all three regions are slightly metal-poor, with marginallysub-solar metallicities, with <[Fe/H]> = -0.11 ± 0.14,-0.10 ± 0.04 and -0.04 ± 0.05 respectively. Conclusions. Asample of stars in several nearby, young star-forming regions has beenestablished, the majority of which is young, lithium rich, magneticallyactive and are non-accreting kinematic members of their respectiveclouds. Within the errors, each region is essentially of solarmetallicity.
| Kinematic Study of the Disrupting Globular Cluster Palomar 5 Using VLT Spectra
Wide-field photometric data from the Sloan Digital Sky Survey haverecently revealed that the Galactic globular cluster Palomar 5 is in theprocess of being tidally disrupted. Here we investigate the kinematicsof this sparse remote star cluster using high-resolution spectra fromthe Very Large Telescope (VLT). Twenty candidate cluster giants locatedwithin 6' of the cluster center have been observed with the UV-VisualEchelle Spectrograph on VLT-UT2. The spectra provide radial velocitieswith a typical accuracy of 0.15 km s-1. We find that thesample contains 17 certain cluster members with very coherentkinematics, two unrelated field dwarfs, and one giant with a deviantvelocity, which is most likely a cluster binary showing fast orbitalmotion. From the confirmed members we determine the heliocentricvelocity of the cluster as -58.7+/-0.2 km s-1. The totalline-of-sight velocity dispersion of the cluster stars is 1.1+/-0.2 kms-1 (all members) or 0.9+/-0.2 km s-1 (stars onthe red giant branch only). This is the lowest velocity dispersion thathas so far been measured for a stellar system classified as a globularcluster. The shape of the velocity distribution suggests that there is asignificant contribution from orbital motions of binaries and that thedynamical part of the velocity dispersion is therefore stillsubstantially smaller than the total dispersion. Comparing theobservations with the results of Monte Carlo simulations of binaries wefind that the frequency of binaries in Pal 5 is most likely between 24%and 63% and that the dynamical line-of-sight velocity dispersion of thecluster must be smaller than 0.7 km s-1 (90% confidence upperlimit). The most probable values of the dynamical dispersion lie in therange 0.12<=σ/km s-1<=0.41 (68% confidence). Pal5 thus turns out to be a dynamically very cold system. Our results arecompatible with an equilibrium system. We find that the luminosity ofthe cluster implies a total mass of only 4.5 to 6.0×103Msolar. We further show that a dynamical line-of-sightvelocity dispersion of 0.32 to 0.37 km s-1 admits a Kingmodel that fits the observed surface density profile of Pal 5 (withW0=2.9 and rt=16.1′) and its mass. Based onobservations obtained at the European Southern Observatory, Paranal,Chile (program 67.D-0298A).
| Cyclic and secular variation in the temperatures and radii of extreme helium stars
The ultraviolet properties of 17 extreme helium stars have been examinedusing 150 IUE spectra. Combining short-wave and long-wave image pairsand using a grid of hydrogen-deficient model atmospheres and aχ2 minimization procedure, 70 measurements of effectivetemperature (Teff), angular diameters (θ) andinterstellar extinction (EB_V) were obtained. In most cases,these were in good agreement with previous measurements, but there aresome ambiguities in the case of the hotter stars, where the solutionsfor Teff and EB_V become degenerate, and in thecase of the cooler stars with large EB_V, where the totalflux is no longer dominated by the ultraviolet. The behaviour of 12helium stars was examined over an interval exceeding 10yr. The surfacesof four stars (HD 168476, HD 160641, BD -9°4395 and BD -1°3438)were found to be heating at rates between 20 and 120Kyr-1, inremarkable agreement with theoretical predictions. This result providesthe first direct evidence that extreme helium stars are heliumshell-burning stars of up to ~0.9Msolar contracting towardsthe white dwarf sequence. Low-luminosity helium stars do not show adetectable contraction, also in agreement with theory, although one, BD+10°2179, may be expanding. The short-term behaviour of threevariable helium stars (PV Tel variables: HD 168476, BD +1°4381, LSIV-1°2) was examined over a short interval in 1995. All three showedchanges in Teff and θ on periods consistent withprevious observations. Near-simultaneous radial velocity (v)measurements were used to establish the total change in radius, withsome reservations concerning the adopted periods. Subsequently,measurements of the stellar radii and distances could be derived. WithTeff and surface gravities established previously, stellarluminosities and masses were thus obtained directly from observation. Inthe case of HD 168476, the mass is 0.94 ± 0.68 M\odot.Assuming a similar gravity for LSIV -1°2 based on its neutral heliumline profiles, its mass becomes 0.79 ± 0.46 M\odot.The θ amplitude for BD +1°4381 appears to be overestimated bythe IUE measurements and leads to a nonsensical result. These firstdirect measurements of luminous extreme helium star masses agree wellwith previous estimates from stellar structure and pulsation theory.
| Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
| High-Precision Radial Velocity Measurements of Some Southern Stars
Precise absolute radial velocities have been obtained at Mount JohnUniversity Observatory for a number of southern stars, using the 1 mtelescope and fiber-fed echelle spectrograph. Only the stars that havebeen observed three or more times are presented, including 14 IAUstandards and 11 program stars. Six echelle orders in the green(5000-5600 Å) are used. Many delicate steps have been undertakenin order to maintain the same conditions in both recording and reducingthe spectra over a period of 27 months. The Th-Ar lamp has been used forthe wavelength calibration. The absolute radial velocities have beendetermined by cross-correlation with synthetic spectra computed by R. L.Kurucz. The zero point has been adjusted using blue-sky spectra. Anadditional strong correlation, between the measured velocities andphoton counts in stellar and Th-Ar spectra, has been detected for thePM3000 CCD camera and has been eliminated. A resulting precision ofabout 20-30 m s-1 has been obtained. The overall uncertaintyof the absolute radial velocities was estimated to be about 100-200 ms-1. The present paper is a continuation of our recentprevious work, including more details on the reduction process and thepresentation of the radial velocities for more stars.
| Radial velocities of HIPPARCOS southern B8-F2 type stars
Radial velocities have been determined for a sample of B8-F2 type starsobserved by the Hipparcos satellite. Observations were obtained withinthe framework of an ESO key-program. Radial velocities have beenmeasured using a cross-correlation method, the templates being a grid ofsynthetic spectra. The obtained precision depends on effectivetemperature and projected rotational velocity of the star as well as ona possible asymmetry of the correlation peak generally due to secondarycomponents. New spectroscopic binaries have been detected from theseasymmetries and the variability of the measured radial velocity.Simulations of binary and triple systems have been performed. Forbinaries our results have been compared with Hipparcos binary data.Adding the variable radial velocities, the minimum binary fraction hasbeen found 60% for physical systems. Radial velocities have beendetermined for 581 B8-F2 stars, 159 being new. Taking into accountpublished radial velocities, 39% south A-type stars with V magnitudelower than 7.5 have a radial velocity. Based on observations obtained atthe European Southern Observatory (ESO, La Silla, Chile) and on datafrom the ESA Hipparcos astrometry satellite.}\fnmsep \thanks{Tables 7, 8and 9 are only available in electronic form at the CDS via anonymous ftpto cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Late-type giants with infrared excess. I. Lithium abundances
de la Reza et al. (1997) suggested that all K giants become Li-rich fora short time. During this period the giants are associated with anexpanding thin circumstellar shell supposedly triggered by an abruptinternal mixing mechanism resulting in the surface Li enrichment. Inorder to test this hypothesis twenty nine late-type giants withfar-infrared excess from the list of Zuckerman et al. (1995) wereobserved in the Li-region to study the connection between thecircumstellar shells and Li abundance. Eight giants have been found tohave log epsilon (Li) > 1.0. In the remaining giants the Li abundanceis found to be much lower. HD 219025 is found to be a rapidly rotating(projected rotational velocity of 23 +/-3 km s(-1) ), dusty and Li-rich(log epsilon (Li) = 3.0+/-0.2) K giant. Absolute magnitude derived fromthe Hipparcos parallax reveals that it is a giant and not apre-main-sequence star. The evolutionary status of HD 219025 seems to besimilar to that of HDE 233517 which is also a rapidly rotating, dustyand Li-rich K giant. The Hipparcos parallaxes of all the well studiedLi-rich K giants show that most of them are brighter than the ``clump"giants. Their position in the H-R diagram indicates that they have gonethrough mixing and the initial abundance of Li is not preserved. Thereseems to be no correlations between Li abundances, rotational velocitiesand carbon isotope ratios. The only satisfactory explanation for theoverabundance of lithium in these giants is the creation of Li by theextra deep mixing and the associated ``cool bottom processing". Based onobservations obtained at the European Southern Observatory, La Silla,Chile, and at the Observatoire de Haute Provence, France.
| Reexamination of the Possible Tidal Stream in Front of the Large Magellanic Cloud
It has recently been suggested that the stars in a vertical extension ofthe red clump feature seen in LMC color-magnitude diagrams could belongto a tidal stream of material located in front of that galaxy. If thisclaim is correct, this foreground concentration of stars couldcontribute significantly to the rate of gravitational microlensingevents observed in the LMC microlensing experiments. Here we presentradial velocity measurements of stars in this so-called ``vertical redclump'' (VRC) population. The observed stellar sample, it transpires,has typical LMC kinematics. It is shown that it is improbable that anintervening tidal stream should have the same distribution of radialvelocities as the LMC, which is consistent with an earlier study thatshows that the VRC feature is more likely a young stellar population inthe main body of that galaxy. However, the kinematic data do notdiscriminate against the possibility that the VRC is an LMC halopopulation.
| The ROSAT all-sky survey catalogue of optically bright late-type giants and supergiants
We present X-ray data for all late-type (A, F, G, K, M) giants andsupergiants (luminosity classes I to III-IV) listed in the Bright StarCatalogue that have been detected in the ROSAT all-sky survey.Altogether, our catalogue contains 450 entries of X-ray emitting evolvedlate-type stars, which corresponds to an average detection rate of about11.7 percent. The selection of the sample stars, the data analysis, thecriteria for an accepted match between star and X-ray source, and thedetermination of X-ray fluxes are described. Catalogue only available atCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Rotation, activity and lithium in NGC 6475
Radial and rotational velocities, chromospheric activity, and lithiumabundances are presented for an X-ray-selected sample of stars in theyoung (220 Myr) open cluster NGC 6475. Low-mass members of the clusterhave been identified on the basis of photometric and spectroscopiccriteria. The observations show that the rapid spindown seen amongsolar-type stars in the Pleiades is incomplete at 220 Myr, as there areF, G, and K stars in NGC 6475 with v sin i greater than 10 km/s. Peakrotation rates for G stars are 12-14 km/s, and are robust to uncertaininclination angles, because the magnetic activity of these stars is lessthan the saturation value observed for fast rotators in the Pleiades.Two mid-K stars are found with v sin i about 25 km/s and with saturatedmagnetic activity levels, indicating that spindown time-scales aremass-dependent, increasing from about 20 Myr for early-G stars togreater than 75 Myr for mid-K stars.
| Barium stars, galactic populations and evolution.
In this paper HIPPARCOS astrometric and kinematical data together withradial velocities from other sources are used to calibrate bothluminosity and kinematics parameters of Ba stars and to classify them.We confirm the results of our previous paper (where we used data fromthe HIPPARCOS Input Catalogue), and show that Ba stars are aninhomogeneous group. Five distinct classes have been found i.e. somehalo stars and four groups belonging to disk population: roughlysuper-giants, two groups of giants (one on the giant branch, the otherat the clump location) and dwarfs, with a few subgiants mixed with them.The confirmed or suspected duplicity, the variability and the range ofknown orbital periods found in each group give coherent resultssupporting the scenario for Ba stars that are not too highly massivebinary stars in any evolutionary stages but that all were previouslyenriched with Ba from a more evolved companion. The presence in thesample of a certain number of ``false'' Ba stars is confirmed. Theestimates of age and mass are compatible with models for stars with astrong Ba anomaly. The mild Ba stars with an estimated mass higher than3Msun_ may be either stars Ba enriched by themselves or``true'' Ba stars, which imposes new constraints on models.
| Absolute magnitudes and kinematics of barium stars.
The absolute magnitude of barium stars has been obtained fromkinematical data using a new algorithm based on the maximum-likelihoodprinciple. The method allows to separate a sample into groupscharacterized by different mean absolute magnitudes, kinematics andz-scale heights. It also takes into account, simultaneously, thecensorship in the sample and the errors on the observables. The methodhas been applied to a sample of 318 barium stars. Four groups have beendetected. Three of them show a kinematical behaviour corresponding todisk population stars. The fourth group contains stars with halokinematics. The luminosities of the disk population groups spread alarge range. The intrinsically brightest one (M_v_=-1.5mag,σ_M_=0.5mag) seems to be an inhomogeneous group containing bariumbinaries as well as AGB single stars. The most numerous group (about 150stars) has a mean absolute magnitude corresponding to stars in the redgiant branch (M_v_=0.9mag, σ_M_=0.8mag). The third group containsbarium dwarfs, the obtained mean absolute magnitude is characteristic ofstars on the main sequence or on the subgiant branch (M_v_=3.3mag,σ_M_=0.5mag). The obtained mean luminosities as well as thekinematical results are compatible with an evolutionary link betweenbarium dwarfs and classical barium giants. The highly luminous group isnot linked with these last two groups. More high-resolutionspectroscopic data will be necessary in order to better discriminatebetween barium and non-barium stars.
| New X-ray sources detected among mild barium and S stars.
We report on the detection by ROSAT of X-rays from the mild barium starHD 165141 (K0III/IIBa1) and from the S stars HD 35155 (S4,1) and HR 363(S3/2). For the S stars, the X-ray flux is attributed to the accretionof the red-giant wind by the white dwarf companion. The strongvariability observed in the X- and UV fluxes on time scales of bothhours and months may be due to irregularities in the accretion rate, orto variable obscuration by cool gas present in the system. In the caseof HD 35155, the absence of ROSAT detection at the phase where eclipsesare observed in the UV and optical domains suggests that part of theX-ray variability may be associated with eclipses of the compactcompanion. HD 165141 is more puzzling since this star seems to share theproperties of RS CVn and barium systems. The properties of the X-raysemitted by this system are typical of RS CVn systems, as is thephotometric period of 35d and the rapid rotation. However, the rapidrotation does not seem to be due to synchronism with the orbital period,as is usually the case for RS CVn systems. The companion appears to be ahot white dwarf rather than a main sequence star, with a long orbitalperiod (~5200d), more typical of barium than of RS CVn systems. Theseconflicting properties could be explained if this particular barium starformed on the giant branch, accreting not only mass but also spinangular momentum. The two giants HR 5692 (G8IIIBa0.3) and HR 6468(G8IIIBa0.6) appear to be coronal X-ray sources. The barium nature ofthese stars is questioned, given their small Ba indices and their normalDDO photometric indices. Moreover, since HR 6468 is a radial-velocitystandard star, it is likely not a binary star as required for bariumstars.
| The red variable star V973 Ophiuchi
Not Available
| 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.
| A kinematic study of the Sculptor dwarf spheroidal galaxy.
We derive new, accurate radial velocity (V_r_) measurements for 23Sculptor K-giant stars from high-resolution echelle spectra made withthe ESO NTT and 3.6-m telescopes. Comparing our velocities with previousmeasurements (Armandroff & Da Costa 1986) for 15 stars, we show thatthe V_r_ measurements are reliable, and discover two V_r_ variable starswith large amplitudes (>17km/s). These variations are best explainedby binary orbital motions. As our sample is likely to contain manyadditional undetected binaries with smaller velocity amplitudes (due toless favorable orbit inclinations, smaller mass ratios, or longerperiods), the observations suggest a large binary fraction in Sculptor,possibly larger than ~20% within the period limits ~0.5 to ~20yrs. Thisresult is consistent with the recent discoveries of 2-3 large-amplitudevariable stars in Ursa Minor and Sextant. Previous kinematic studies ofdSph galaxies based on single-epoch measurements are consequently notfully reliable. Radial velocity-variable stars artificially inflate thevelocity dispersion and the mass-to-light (M/L) ratio estimates. Thisweakens the case for dark matter, at least in some of the dSph galaxies.In the case of Sculptor, a velocity dispersion of 6.2+/-1.1km/s and aM/L ratio of 13+/-6(M/L_V_)sun_ are derived from our sample.These results do not provide unambiguous evidence for a dominant darkmatter component in Sculptor, mainly because our sample is likely tocontain additional undetected V_r_ variables of lower amplitude.
| Lucifers, a photoelectric radial-velocity spectrometer
A spectrometer dedicated to the measurement of stellar radial velocitieshas been developed at the University of Canterbury and the Mt JohnUniversity Observatory. The spectrometer scans a spectrum from theObservatory's 1-meter McLellan reflecting telescope and fiber-fedechelle with an oscillating mask having 2447 rectangular slotsrepresenting absorption lines in the spectrum of the star Alpha CentauriA covered by the wavelength range 397 to 570 nm in orders 40 to 58 ofthe spectrograph and measures the light passing through the mask as afunction of mask position. A dedicated computer constructs across-correlation function to which a Gaussian distribution function isfitted. The difference between the radial velocities of a star and azero-velocity reference spectrum provided by a hollow-cathode ironemission lamp is calculated from the Gaussian parameters. The sources ofrandom error in the system are discussed and its magnitude for stars ofspectral types F0 to M3.5 is estimated. Systematic errors in the systemare also discussed.
| Identification of V1017 SGR as a cataclysmic variable binary system with unusually long period
A preliminary spectroscopic orbit determination with period 5.7 days isreported for V1017 Sgr, the remnant of nova Sagittarii 1919. This ismuch longer than the typical periods of cataclysmic binaries, which aregenerally less than 0.5 day. It is suggested that V1017 Sgr, along witha few other systems of unusually long period such as BV Cen and GK Per,may form a distinct class of cataclysmic variables characterized bytheir larger, more resolved secondaries.
| Taxonomy of barium stars
Spectral classification, barium intensity, radial velocity, luminosity,and kinematical properties are determined for 389 barium stars byanalyzing image-tube spectra and photometric observation data. Diskkinematics for the stars are based on whether they are Ba weak or Bastrong. Weak barium stars in general have smaller velocity dispersions,brighter apparent magnitude, and lower luminosity than strong bariumstars. These characteristics are confirmed by solving for meanspectroscopic distances, z-scale height distances, and reduced propermotions.
| The dynamics and structure of rich clusters of galaxies. I - Velocity data
An extensive spectroscopic study of 10 rich southern X-ray clusters ofgalaxies is presented. Between 40 and 200 redshifts have been obtainedin the field of each of the clusters, which cover a wide range ofmorphological types and richnesses. Applying rigorous statisticalanalyses to the total data base of 1000 precise radial velocitiesprovides the necessary information to undertake a thorough dynamicalinvestigation of these individual clusters and of cluster systems ingeneral.
| Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.
| The Mass Distribution in the Galactic Disc - Part Two - Determination of the Surface Mass Density of the Galactic Disc Near the Sun
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1989MNRAS.239..605K&db_key=AST
| 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.
| 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.
| Radial velocities of bright southern stars. VI - Standard and reference stars 1983-1986
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1987A&AS...68..347A&db_key=AST
| Radial velocities of CaII emission stars - Photographic data
Photographically determined radial velocities are given for eighteenstars selected from lists of G, K and M stars with strong CaII emissionreversals. The results of observations of radial velocity standards arealso given.
| About the stability of the spectrograph of the 1-m Yale telescope at Cerro Tololo.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1986RMxAA..13....3L&db_key=AST
| Three-dimensional structure in field 349 of the southern sky survey. I - Redshifts for a magnitude-limited sample of galaxies from slit spectra
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1986MNRAS.220..901P&db_key=AST
| Active regions on HR 1099 from a high resolution spectroscopic study of photospheric (Fe I) and chromospheric (Ca II and H-alpha) lines
The Doppler imaging technique applied to photospheric (Fe I) absorptionlines and chromospheric (Ca II IR and H-alpha) emission lines of the HR1099 (V711 Tau) RSCVn system shows that, on the primary star,photospheric spots 1000 K cooler than the surrounding photosphere coverabout 20 percent of the stellar disk and are overlapped with brightsolar-like chromospheric plages. The location and extent of these activecenters suggest the existence of important magnetic flux at relativelyhigh latitudes of the K 1 IV primary star. A speculative model in whichmaterial is driven from one active region to the other along magneticfield lines is suggested by the geometry of the system and canespecially account for the H-alpha profile structure and the degree ofpolarization at radio frequencies observed in HR 1099.
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Osservazione e dati astrometrici
| Costellazione: | Altare |
| Ascensione retta: | 17h26m00.00s |
| Declinazione: | -50°38'01.0" |
| Magnitudine apparente: | 5.23 |
| Distanza: | 122.1 parsec |
| Moto proprio RA: | 14.2 |
| Moto proprio Dec: | 9.6 |
| B-T magnitude: | 6.521 |
| V-T magnitude: | 5.309 |
Cataloghi e designazioni:
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