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The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics
Context: Ages, chemical compositions, velocity vectors, and Galacticorbits for stars in the solar neighbourhood are fundamental test datafor models of Galactic evolution. The Geneva-Copenhagen Survey of theSolar Neighbourhood (Nordström et al. 2004; GCS), amagnitude-complete, kinematically unbiased sample of 16 682 nearby F andG dwarfs, is the largest available sample with complete data for starswith ages spanning that of the disk. Aims: We aim to improve theaccuracy of the GCS data by implementing the recent revision of theHipparcos parallaxes. Methods: The new parallaxes yield improvedastrometric distances for 12 506 stars in the GCS. We also use theparallaxes to verify the distance calibration for uvby? photometryby Holmberg et al. (2007, A&A, 475, 519; GCS II). We add newselection criteria to exclude evolved cool stars giving unreliableresults and derive distances for 3580 stars with large parallax errorsor not observed by Hipparcos. We also check the GCS II scales of T_effand [Fe/H] and find no need for change. Results: Introducing thenew distances, we recompute MV for 16 086 stars, and U, V, W,and Galactic orbital parameters for the 13 520 stars that also haveradial-velocity measurements. We also recompute stellar ages from thePadova stellar evolution models used in GCS I-II, using the new valuesof M_V, and compare them with ages from the Yale-Yonsei andVictoria-Regina models. Finally, we compare the observed age-velocityrelation in W with three simulated disk heating scenarios to show thepotential of the data. Conclusions: With these revisions, thebasic data for the GCS stars should now be as reliable as is possiblewith existing techniques. Further improvement must await consolidationof the T_eff scale from angular diameters and fluxes, and the Gaiatrigonometric parallaxes. We discuss the conditions for improvingcomputed stellar ages from new input data, and for distinguishingdifferent disk heating scenarios from data sets of the size andprecision of the GCS.Full Table 1 is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/501/941
| Pre-main sequence spectroscopic binaries suitable for VLTI observations
Context: A severe problem for research in star-formation is that themasses of young stars are almost always estimated from evolutionarytracks alone. Since the tracks published by different groups differ, itis often only possible to give a rough estimate of the masses of youngstars. It is thus crucial to test and calibrate the tracks. Up to now,only a few tests of the tracks could be carried out. However, it is nowpossible with the VLTI to set constrains on the tracks by determiningthe masses of many young binary stars precisely. Aims: In order to usethe VLTI efficiently, a first step is to find suitable targets, which isthe purpose of this work. Given the distance of nearby star-formingregions, suitable VLTI targets are binaries with orbital periods betweenat least 50 days and a few years. Although a number of surveys fordetecting spectroscopic binaries have been carried out, most of thebinaries found so far have periods that are too short. Methods: We thussurveyed the Chamaeleon, Corona Australis, Lupus, Sco-Cen, and ρOphiuci star-forming regions in order to search for spectroscopicbinaries with periods longer than 50 days, which are suitable for theVLTI observations. Results: As a result of the 8 year campaign, wediscovered 8 binaries with orbital periods longer than 50 days. Amongstthe newly discovered long-period binaries is CS Cha, which is one of thefew classical T Tauri stars with a circumbinary disk. The survey islimited to objects with masses higher than 0.1 to 0.2 M_ȯ forperiods between 1 and 8 years. Conclusions: We find that the frequencyof binaries with orbital periods ≤3000 days is of 20±5%. Thefrequency of long and short period pre-main sequence spectroscopicbinaries is about the same as for stars in the solar neighbourhood. Intotal 14 young binaries are now known that are suitable for massdetermination with the VLTI.based on observations obtained at the European Southern Observatory atLa Silla, Chile in program 62.I-0418(A); 63.I-0096(A); 64.I-0294(A);65.I-0012(A); 67.C-0155(A); 68.C-0292(A); 68.C-0561(A); 69.C-0207(A);70.C-0163(A); 073.C-0355(A); 074.A-9018(A); 075.C-0399(A-F). Tables 2,3, 5, 6, 8, 10, 12-20 are only available in electronic form athttp://www.aanda.org
| Search for associations containing young stars (SACY). I. Sample and searching method
We report results from a high-resolution optical spectroscopic surveyaimed to search for nearby young associations and young stars amongoptical counterparts of ROSAT All-Sky Survey X-ray sources in theSouthern Hemisphere. We selected 1953 late-type (B-V~≥~0.6),potentially young, optical counterparts out of a total of 9574 1RXSsources for follow-up observations. At least one high-resolutionspectrum was obtained for each of 1511 targets. This paper is the firstin a series presenting the results of the SACY survey. Here we describeour sample and our observations. We describe a convergence method in the(UVW) velocity space to find associations. As an example, we discuss thevalidity of this method in the framework of the β Pic Association.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| The infrared void in the Lupus dark clouds revisited: a polarimetric approach
The results of B-band CCD imaging linear polarimetry obtained for starsfrom the Hipparcos catalogue are used to re-examine the distribution ofthe local interstellar medium towards the IRAS 100-μm emission voidin the Lupus dark clouds. The analysis of the obtainedparallax-polarization diagram assigns to the dark cloud Lupus1 adistance between 130 and 150pc and assures the existence of a low columndensity region coincident with the observed infrared void. Moreover,there are clear indications of the existence of absorbing material atdistances closer than 60-100pc, which may be associated with theinterface boundary between the Local Bubble and its neighbourhood LoopIsuperbubble.
| A catalogue of eclipsing variables
A new catalogue of 6330 eclipsing variable stars is presented. Thecatalogue was developed from the General Catalogue of Variable Stars(GCVS) and its textual remarks by including recently publishedinformation about classification of 843 systems and making correspondingcorrections of GCVS data. The catalogue1 represents thelargest list of eclipsing binaries classified from observations.
| The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of 14 000 F and G dwarfs
We present and discuss new determinations of metallicity, rotation, age,kinematics, and Galactic orbits for a complete, magnitude-limited, andkinematically unbiased sample of 16 682 nearby F and G dwarf stars. Our63 000 new, accurate radial-velocity observations for nearly 13 500stars allow identification of most of the binary stars in the sampleand, together with published uvbyβ photometry, Hipparcosparallaxes, Tycho-2 proper motions, and a few earlier radial velocities,complete the kinematic information for 14 139 stars. These high-qualityvelocity data are supplemented by effective temperatures andmetallicities newly derived from recent and/or revised calibrations. Theremaining stars either lack Hipparcos data or have fast rotation. Amajor effort has been devoted to the determination of new isochrone agesfor all stars for which this is possible. Particular attention has beengiven to a realistic treatment of statistical biases and errorestimates, as standard techniques tend to underestimate these effectsand introduce spurious features in the age distributions. Our ages agreewell with those by Edvardsson et al. (\cite{edv93}), despite severalastrophysical and computational improvements since then. We demonstrate,however, how strong observational and theoretical biases cause thedistribution of the observed ages to be very different from that of thetrue age distribution of the sample. Among the many basic relations ofthe Galactic disk that can be reinvestigated from the data presentedhere, we revisit the metallicity distribution of the G dwarfs and theage-metallicity, age-velocity, and metallicity-velocity relations of theSolar neighbourhood. Our first results confirm the lack of metal-poor Gdwarfs relative to closed-box model predictions (the ``G dwarfproblem''), the existence of radial metallicity gradients in the disk,the small change in mean metallicity of the thin disk since itsformation and the substantial scatter in metallicity at all ages, andthe continuing kinematic heating of the thin disk with an efficiencyconsistent with that expected for a combination of spiral arms and giantmolecular clouds. Distinct features in the distribution of the Vcomponent of the space motion are extended in age and metallicity,corresponding to the effects of stochastic spiral waves rather thanclassical moving groups, and may complicate the identification ofthick-disk stars from kinematic criteria. More advanced analyses of thisrich material will require careful simulations of the selection criteriafor the sample and the distribution of observational errors.Based on observations made with the Danish 1.5-m telescope at ESO, LaSilla, Chile, and with the Swiss 1-m telescope at Observatoire deHaute-Provence, France.Complete Tables 1 and 2 are 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/418/989
| Key parameters of W UMa-type contact binaries discovered by HIPPARCOS
A sample of W UMa-type binaries which were discovered by the HIPPARCOSsatellite was constructed with the aid of well defined selectioncriteria described in this work. The selection process showed up thatseveral systems of which the variability types have been assigned as EBin HIPPARCOS catalogue are genuine contact binaries of W UMa-type. Thelight curves of the 64 selected systems based on HIPPARCOS photometrywere analyzed with the aid of light curve synthesis method by Rucinskiand their geometric elements (namely mass ratio q, degree of contact f,and orbital inclination i) were determined. The solutions were obtainedfor the first time for many of the systems in the sample and would be agood source for their future light curve analyses based on more precisefollow-up observations.Based on observations made with the ESA HIPPARCOSastrometry satellite.
| The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
| SANTIAGO 91, a right ascension catalogue of 3387 stars (equinox J2000).
The positions in right ascension of 3387 stars belonging to the Santiago67 Catalogue, observed with the Repsold Meridian Circle at Cerro Calan,National Astronomical Observatory, during the period 1989 to 1994, aregiven. The average mean square error of a position, for the wholeCatalogue, is +/-0.009 s. The mean epoch of the catalogue is 1991.84.
| A large, complete, volume-limited sample of G-type dwarfs. I. Completion of Stroemgren UVBY photometry
Four-colour photometry of potential dwarf stars of types G0 to K2,selected from the Michigan Spectral Catalogues (Vol. 1-3), has beencarried out. The results are presented in a catalogue containing 4247uvby observations of 3900 stars, all south of δ = -26deg. Theoverall internal rms errors of one observation (transformed to thestandard system) of a program star in the interval 8.5 < V < 10.5are 0.0044, 0.0021, 0.0039, and 0.0059, respectively, in V, b-y, m_1_ ,and c_1_. The purpose of the catalogue, combined with earliercatalogues, is to allow selection of a large, complete, volume-limitedsample of G- and K-type dwarfs, investigate their metallicitydistribution, and compare it to predictions of various models ofgalactic chemical evolution. Future papers in this series will discussthese subjects.
| 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.
| Jupiter and Galilean satellites' positions obtained in April 1978 with the GPO 40 CM /f = 4 m/ of the ESO, La Silla
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&AS...40..375D&db_key=AST
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| קבוצת-כוכבים: | מאזניים |
| התרוממות ימנית: | 15h29m26.87s |
| סירוב: | -28°50'52.3" |
| גודל גלוי: | 8.729 |
| מרחק: | 89.686 פארסק |
| תנועה נכונה: | -52 |
| תנועה נכונה: | -59.5 |
| B-T magnitude: | 9.649 |
| V-T magnitude: | 8.805 |
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