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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
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Contact Binaries with Additional Components. I. The Extant Data
We have attempted to establish observational evidence for the presenceof distant companions that may have acquired and/or absorbed angularmomentum during the evolution of multiple systems, thus facilitating orenabling the formation of contact binaries. In this preliminaryinvestigation we use several techniques (some of themdistance-independent) and mostly disregard the detection biases ofindividual techniques in an attempt to establish a lower limit to thefrequency of triple systems. While the whole sample of 151 contactbinary stars brighter than Vmax=10 mag gives a firm lowerlimit of 42%+/-5%, the corresponding number for the much better observednorthern-sky subsample is 59%+/-8%. These estimates indicate that mostcontact binary stars exist in multiple systems.
| 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
| Improved Astrometry and Photometry for the Luyten Catalog. II. Faint Stars and the Revised Catalog
We complete construction of a catalog containing improved astrometry andnew optical/infrared photometry for the vast majority of NLTT starslying in the overlap of regions covered by POSS I and by the secondincremental Two Micron All Sky Survey (2MASS) release, approximately 44%of the sky. The epoch 2000 positions are typically accurate to 130 mas,the proper motions to 5.5 mas yr-1, and the V-J colors to0.25 mag. Relative proper motions of binary components are measured to 3mas yr-1. The false-identification rate is ~1% for11<~V<~18 and substantially less at brighter magnitudes. Theseimprovements permit the construction of a reduced proper-motion diagramthat, for the first time, allows one to classify NLTT stars intomain-sequence (MS) stars, subdwarfs (SDs), and white dwarfs (WDs). We inturn use this diagram to analyze the properties of both our catalog andthe NLTT catalog on which it is based. In sharp contrast to popularbelief, we find that NLTT incompleteness in the plane is almostcompletely concentrated in MS stars, and that SDs and WDs are detectedalmost uniformly over the sky δ>-33deg. Our catalogwill therefore provide a powerful tool to probe these populationsstatistically, as well as to reliably identify individual SDs and WDs.
| The 7.5 Magnitude Limit Sample of Bright Short-Period Binary Stars. I. How Many Contact Binaries Are There?
A sample of bright contact binary stars (W UMa type or EW, and related:with β Lyr light curves, EB, and ellipsoidal, ELL-in effect, allbut the detached, EA) to the limit of Vmax=7.5 mag is deemedto include all discoverable short-period (P<1 day) binaries withphotometric variation larger than about 0.05 mag. Of the 32 systems inthe final sample, 11 systems have been discovered by the Hipparcossatellite. The combined spatial density is evaluated at(1.02+/-0.24)×10-5 pc-3. The relativefrequency of occurrence (RFO), defined in relation to the main-sequencestars, depends on the luminosity. An assumption of RFO~=1/500 forMV>+1.5 is consistent with the data, although the numberstatistics is poor with the resulting uncertainty in the spatial densityand the RFO by a factor of about 2. The RFO rapidly decreases forbrighter binaries to a level of 1/5000 for MV<+1.5 and to1/30,000 for MV<+0.5. The high RFO of 1/130, previouslydetermined from the deep OGLE-I sample of disk population W UMa typesystems toward Baade's window, is inconsistent with and unconfirmed bythe new results. Possible reasons for the large discrepancy arediscussed. They include several observational effects but also apossibility of a genuine increase in the contact-binary density in thecentral parts of the Galaxy. Based on data from the Hipparcos satellitemission and from the David Dunlap Observatory, University of Toronto.
| On the Variability of A3-F0 Luminosity Class III-V Stars
I investigate the Hipparcos Satellite photometry of A3-F0 stars ofluminosity classes III-V to learn about their variability and identify afew stars for which further study is desirable.
| ICCD Speckle Observations of Binary Stars. XXIII. Measurements during 1982-1997 from Six Telescopes, with 14 New Orbits
We present 2017 observations of 1286 binary stars, observed by means ofspeckle interferometry using six telescopes over a 15 year period from1982 April to 1997 June. These measurements constitute the 23dinstallment in CHARA's speckle program at 2 to 4 m class telescopes andinclude the second major collection of measurements from the MountWilson 100 inch (2.5 m) Hooker Telescope. Orbital elements are alsopresented for 14 systems, seven of which have had no previouslypublished orbital analyses.
| A common resonance of delta SCT stars and ellipsoidal binaries.
Not Available
| The δ Scuti star θ Tucanae. II. UVBY colour variations and pulsational/orbital properties.
On the basis of almost 1500 uvby photometric observations of θTucanae collected in 1993, we discuss the colour variation of thismulti-periodic δ Scuti star and debate some of its binary andpulsational properties. The frequencies f_1_=0.281 and f_2_=0.142c/dembody orbital motion in a 7.04d day ellipsoidal configurationcharacterised by a light curve with unequal maxima and minima and acolour index that becomes bluer during the minimum phases. The firstresults of an analysis of the light curve points towards a mass ratio qof the order of 0.10-0.15. We present dependable numerical values forcolour phase differences and amplitude ratios A_b-y_/A_y_,φ_b-y_-φ_y_, A_v-y_/A_y_, φ_v-y_-φ_y_ andA_u-y_/A_y_, φ_u-y_-φ_y_ which can be used for pulsation-modeidentification. The principal pulsation frequency f_7_=20.28c/d isreconcilable with a radial mode.
| On rotation of ellipsoidal binary systems.
Not Available
| Complex behaviour of the δ Scuti star θ Tucanae. I. Frequencies in the light variation.
On the basis of more than 2300 new Stroemgren y and Johnson Vphotometric observations collected during 246 hours spread over 42nights at three sites in 1993, we present a frequency analysis of thelight variation of θ Tuc. 10 frequencies were found in the rangeof 15.8 to 20.28cycles/day displaying an extreme regularity. Frequenciesare situated in groups and these groups are equally spaced. Some kind ofsplitting is definitely involved. The frequencies are constant inamplitude on a short time scale. Two frequencies, 0.282 and0.142cycles/day (3.56 and 7.04days period) were found to be responsiblefor the mean light level variation of θ Tuc. Although θTuc is known as a single star, the length and shape of the mean lightlevel variation and the unusual behaviour of θ Tuc in ultravioletand infrared suggest that the δ Scuti star θ Tuc is aprimary in a binary system with a late F type companion.
| Stellar Pulsations Across the HR Diagram: Part 2
Stars over essentially the whole mass domain can become pulsationallyunstable during various stages of their evolution. They will appear asvariable stars with characteristics that are of much diagnostic value toastronomers. The analysis of such observations provides a challengingand unique approach to study aspects of the internal constitution andevolutionary status of these objects that are not accessible otherwise.This review touches on most classes of known pulsating variable starsand tries to elucidate connections to stellar physical aspects. To aidfuture investigations, we stress questions and problems that we believeare yet to be resolved satisfactorily.
| 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 List of Variable Stars Similar to gamma Dor
Not Available
| 9 Aurigae: strong evidence for non-radial pulsations
We present further photometric observations of the unusual F0 V star 9Aurigae and present evidence that this star's radial velocity,spectroscopic line widths and line depths are also variable with thesame frequencies as the photometric data (f_1~=0.795 and f_2~=0.345d^-1). The phases of these sinusoids are stable over time-scales oflonger than one year, though the amplitudes can vary, making theprediction of photometric behaviour impossible. Given that a variety ofother explanations have already been discounted (e.g. interactions witha close companion, the existence of a lumpy, orbiting ring of dust, orstar spots) and that these variations occur on time-scales an order ofmagnitude slower than the fundamental radial pulsation period, we havevery strong evidence that 9 Aurigae exhibits non-radial g-modepulsations. Since the power spectrum of the radial velocity data showsfrequency f_2 but does not clearly show f_1, the present data suggestthat f_2 is associated with a low-degree spherical harmonic L=1 or 2),while f_1 is associated with a higher degree harmonic. 9 Aurigae, alongwith such stars as gamma Doradus, HD 224638, HD 224945, and HD 164615,appears to constitute a new class of pulsating variables. These starsare to be found at or beyond the cool edge of the Cepheid instabilitystrip in the HR Diagram. Prior to this, only much hotter stars have beenshown to exhibit non-radial g-modes.
| HD 96008: an ellipsoidal variable star, not an unusual F-type variable.
High-precision radial-velocity measurements of the star HD 96008 haveallowed us to establish that this object, supposed by some authors tobelong to a new class of unusual F0-type variable stars, is actually anellipsoidal variable. By combining photometric and spectroscopic data ithas been possible to derive the physical parameters of the systemcharacterized by a low mass ratio and seen under a small angle ofinclination: it consists of an F0 subgiant almost filling its Roche lobeand an M5 star at 3.6Rsun_ from the primary.
| The general catalogue of trigonometric [stellar] paralaxes
Not Available
| The sign of four : a new class of cool non-radially pulsating stars ?
In this paper we discuss four early F-type variable stars whose periodsare an order of magnitude slower than known pulsators of comparableluminosity. They cannot be stars undergoing simple radial pulsations.For one or more of these stars we can discount the possibility that thevariability is due to rotational modulation of star spots, interactionswith (or tidal distortions by) a close companion, or obscuration by arotating lumpy ring of dust orbiting the star. They are certainly noteclipsing binaries. The only possibility left seems to be non-radialpulsations, though this explanation involves difficulties of its own. Ifthey are indeed pulsating stars exhibiting non- radial gravity modes,they would be the first stars on the cool side of the Cepheidinstability strip in the Hertzsprung-Russell Diagram to be soidentified.
| A new class of pulsating stars
Until recently, no stars on the cool side of the Cepheid instabilitystrip in the HR diagram (with the possible exception of the Sun) havebeen suspected of exhibiting non-radial gravity modes. For example, 53Persei (Sp = B4 IV) has Teff ~ 16,000\ K and the DOV star PG1159-035 has Teff ~ 123,000\ K. The papers listed below (andreferences therein) present a dozen stars which are typically early Fstars of luminosity class V or IV-V and which are photometricallyvariable up to 0.1 magnitude, with periods ranging from 0.3 to 1.8 days(an order of magnitude slower than one would expect of stars of thisspectral type and luminosity class undergoing simple radial pulsations).9 Aurigae (Sp = F0 V, Teff ~ 7200\ K, per = 1.277 days) hasshown evidence of radial velocity variations of order 6 km/sec andpossible line profile variations. gamma Doradus, which has two periodsnear 0.75 days, has definitely shown line profile variations. For HD96008 the notion of rotational modulation is ruled out because itsphotometric period would imply an equatorial rotational speed of 330km/sec -- incompatible with its having sharp spectral lines. 9 Aurigaeand HD 224638 (Sp ~ F0, per = 1.47 days) have both shown sudden phaseshifts in their light curves. Having eliminated a number ofpossibilities for individual stars, I conclude that these stars areeither exhibiting non-radial g-modes, or we are confronted with acompletely new physical mechanism for producing light variations instars. We present preliminary results of ongoing observations of some ofthese stars. Antonello, E., and Mantegazza, L. 1986, Astron. Astrophys.164, 40. Balona, L. A. et al. 199[3], Monthly Not. R. A. S., in press.Krisciunas, K. et al. \ 1993, Monthly Not. R. A. S. \ 263, 781.Krisciunas, K. 1993, Comments on Astrophys. \ 17, no. 4, in press.Mantegazza, L. et al. \ 1991, IBVS 3612. Mantegazza, L., and Poretti, E.1991, IBVS 3690. Mantegazza, L. et al. \ 1993, in Inside the Stars, ASPConf. Series 40, 651.
| The 9-AURIGAE System
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993MNRAS.263..781K&db_key=AST
| Gamma Doradus
Not Available
| Early type high-velocity stars in the solar neighborhood. IV - Four-color and H-beta photometry
Results are presented from photometric obaservations in the Stromgrenuvby four-color and H-beta systems of early-type high-velocity stars inthe solar neighborhood. Several types of photometrically peculiar starsare selected on the basis of their Stromgren indices and areprovisionally identified as peculiar A stars, field horizontal-branchstars, metal-poor stars near the Population II and old-disk turnoffs,metal-poor blue stragglers, or metallic-line A stars. Numerousphotometrically normal stars were also found.
| HD96008 - Variable without a cause
New photometry of HD96008 is reported which reveals that the star has anasymmetric light curve with a period near 0.31 d. Analysis of the dataof Lampens (1987), combined with the new data, produces a period of0.309873 + or - 0.000005 d. At present, there is no explanation for thevariations of the star which can be reconciled with all the availabledata.
| The 69th Name-List of Variable Stars
Not Available
| Photoelectric study of HD 96008 - A close binary system or a new pulsating star?
About one hundred photometric observations in the Geneva PhotometricSystem have been obtained for HD 96008. A Fourier analysis and phasedispersion minimization technique have been used in order to derive afrequency of 3.22994±0.00013 c/d (corresponding to a 0.31 daysperiod) or one half frequency of 1.61948±0.00013 c/d(corresponding to a 0.62 days period). The nature of HD 96008 is atpresent unclear: either it is a close binary system with ellipsoidalcomponents, having the very short orbital period of 0.62 days and thesmall total amplitude of 0.025 mag, or it is a pulsator with a period of0.31 days, which is rather long for a pulsation of the Delta Scuti type.
| Early-type high-velocity stars in the solar neighborhood. III - Radial velocities, rotation indices, and line-strength indices for southern candidates
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1983AJ.....88.1349S&db_key=AST
| Early-type high-velocity stars in the solar neighborhood. II Photometry for 78 candidates
H-beta and four-color photometry are presented for 78 early-type,high-velocity star candidates consisting of: (1) 74 candidates listed ina previous paper; and (2) four candidates identified by Eggen (1970).All of the sample appears to be near the main sequence, with theexception of five of the AO-type stars that are probably on the fieldPopulation II horizontal branch. Almost one-third of the main-sequence Astars and nearly all of the F stars are seen as true high-velocityobjects, and several of the high-velocity F stars appear to have solarmetal abundances. The existence of young, metal-rich, high-velocitystars is supported by the data, and it is concluded that this populationmay contribute one A star to every thousand stars in the solarneighborhood.
| The Evolutionary Status of the Blue Halo Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973ApJS...26...37N&db_key=AST
| Radial velocities and three-colour photometry of 166 southern stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1965MNRAS.131...95P&db_key=AST
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