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Radial Velocity Studies of Southern Close Binary Stars. I. Winter Systems
Radial velocity measurements and sine-curve fits to the orbital velocityvariations are presented for nine contact binaries: V1464 Aql, V759 Cen,DE Oct, MW Pav, BQ Phe, EL Aqr, SX Crv, VZ Lib, and GR Vir. For thefirst five of these, our observations are the first available radialvelocity data. For the three remaining radial velocity variables, CE Hyiis a known visual binary, while CL Cet and V1084 Sco are suspected to bemultiple systems in which the contact binary is spectrally dominated byits companion (which itself is a binary in V1084 Sco). Five additionalvariable stars, V872 Ara, BD Cap, HIP 69300, BX Ind, and V388 Pav, areof unknown type, but most are pulsating stars; we give their mean radialvelocities and Vsini.Based on data obtained at the European Southern Observatory.
| Establishing Observational Baselines for Two δ Scuti Variables: V966 Herculis and V1438 Aquilae
We have examined the previously understudied δ Scuti stars V966Herculis and V1438 Aquilae. We find that V966 Her is a stable pulsatorwith a refined period of 0.1330302 days with a full V amplitude of 0.096mag. We also find that V966 Her has an average radial velocity of +7.8km s-1, a full radial velocity amplitude of 7.6 kms-1, and a vsini=63.8 km s-1. For V1438 Aql wereport a revised Hipparcos period of 0.1612751 days with a fullamplitude of 0.056. The average radial velocity is found to be -43 kms-1, with full amplitude of 9.7 km s-1, and avsini=76.7 km s-1. Due to some anomalies seen in V1438 Aql wefeel that a much larger photometric and spectroscopic campaign isrequired to determine the true nature of this star.
| Monitoring Three Less-Studied δ Scuti Variables: GW Ursae Majoris, BO Lyncis, and AN Lyncis
We present results from monitoring three δ Scuti variables. GW UMais found to be a stable, monoperiodic, high-amplitude δ Scutivariable with a revised period of 0.20319389 days. We also report a fullradial velocity curve, a near-solar metal content, and a rotationalvelocity of 15+/-5 km s-1. From a very short time line wefind that BO Lyn has a constant period change of-1.5×10-10 days day-1. We also find twopotential secondary frequencies of f2=15.81 andf3=13.60 cycles day-1. Finally, we report someunusual results for AN Lyn. We show that the period and amplitude arechanging in phase and that this change is related to a binary companion.
| 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
| A revised catalogue of delta Sct stars
An extensive and up-dated list of delta Sct stars is presented here.More than 500 papers, published during the last few years, have beenrevised and 341 new variables have been added to our last list, sixyears ago. This catalogue is intended to be a comprehensive review onthe observational characteristics of all the delta Sct stars known untilnow, including stars contained in earlier catalogues together with othernew discovered variables, covering information published until January2000. In summary, 636 variables, 1149 references and 182 individualnotes are presented in this new list. Tables 1 and 2 will be accessibleonly 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
| The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
| The discovery of new gamma Doradus stars from the HIPPARCOS mission
We present a classification of 39 new variable stars with spectral typebetween A2 and F8 discovered by Hipparcos with the aim to find new gammaDoradus stars. We have used a multivariate classification scheme andreport the discovery of 14 new gamma Doradus variables among thisunbiased sample. Our results point out the biased nature towards hottemperatures of earlier, ground-based surveys of these variables. Thecoolest star among our sample has an effective temperature only slightlyhotter than 6 000 K. For most of the 14 new gamma Doradus stars, we areable to detect more than one period in the Hipparcos light curve. Themultiperiodicity points towards the presence of high-order g-modes. Inview of the lack of a pulsation mechanism for these objects, wedetermine their position in the HR diagram with respect to the deltaScuti stars.
| True and Possible Contact Binaries in the Hipparcos Catalogue
A comprehensive list of contact binaries included in the HIPPARCOScatalogue is given.
| 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.
| Estimation of spectral classifications for bright southern stars with interesting Stromgren indices
This 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.
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Pozíciós és asztrometriai adatok
| Csillagkép: | Bak |
| Rektaszcenzió: | 20h10m06.76s |
| Deklináció: | -25°17'02.4" |
| Vizuális fényesség: | 7.452 |
| Távolság: | 202.84 parszek |
| RA sajátmozgás: | 24.4 |
| Dec sajátmozgás: | -8.9 |
| B-T magnitude: | 7.951 |
| V-T magnitude: | 7.494 |
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