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Effective temperature scale and bolometric corrections from 2MASS photometry
We present a method to determine effective temperatures, angularsemi-diameters and bolometric corrections for population I and II FGKtype stars based on V and 2MASS IR photometry. Accurate calibration isaccomplished by using a sample of solar analogues, whose averagetemperature is assumed to be equal to the solar effective temperature of5777 K. By taking into account all possible sources of error we estimateassociated uncertainties to better than 1% in effective temperature andin the range 1.0-2.5% in angular semi-diameter for unreddened stars.Comparison of our new temperatures with other determinations extractedfrom the literature indicates, in general, remarkably good agreement.These results suggest that the effective temperaure scale of FGK starsis currently established with an accuracy better than 0.5%-1%. Theapplication of the method to a sample of 10 999 dwarfs in the Hipparcoscatalogue allows us to define temperature and bolometric correction (Kband) calibrations as a function of (V-K), [m/H] and log g. Bolometriccorrections in the V and K bands as a function of T_eff, [m/H] and log gare also given. We provide effective temperatures, angularsemi-diameters, radii and bolometric corrections in the V and K bandsfor the 10 999 FGK stars in our sample with the correspondinguncertainties.
| 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
| The Pul-3 catalogue of 58483 stars in the Tycho-2 system
A catalogue of positions and proper motions of 58483 stars (Pul-3) hasbeen constructed at the Pulkovo observatory. The Pul-3 is based on theresults of measurements of photographic plates with galaxies (Deutsch'splan). All plates were taken using the Pulkovo Normal Astrograph (thefirst epoch is in the 1950s and the second epoch is in the 1970s).The Pul-3 catalogue contains stars of mainly 12 to 16.5 mag in 146fields with galaxies in the declination zone from -5o to+85o. The Tycho-2 has been used as a reference catalogue.The mean epoch of the Pul-3 is 1963.25. The internal positional accuracyof the Pul-3 catalogue at the mean epoch of observations is ±80mas. The accuracy of the proper motions is mostly within ±3mas/yr to ±12 mas/yr. Comparisons of the Pul-3 with Tycho-2 andARIHIP have been done at the mean epoch of the Pul-3. The Pul-3 externalpositional accuracy relative to Tycho-2 is ±150 mas.The catalogue 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/418/357
| GPM - compiled catalogue of absolute proper motions of stars in selected areas of sky with galaxies.
Not Available
| Photoelectric photometry of stars in the Vilnius system in Kapteyn areas SA 2, 4 and 6
Photoelectric photometry in the Vilnius system of 114 standard stars inKapteyn areas SA 2, 4, and 6 is presented with mean square errors of thearithmetic mean +/- 0.005 mag. Photometrically determined spectral typesand luminosity classes of the stars are also presented.
| 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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משמש של הקבוצה הבאה
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | ג'ירף |
| התרוממות ימנית: | 07h47m39.58s |
| סירוב: | +73°59'30.5" |
| גודל גלוי: | 8.105 |
| מרחק: | 67.889 פארסק |
| תנועה נכונה: | -7.7 |
| תנועה נכונה: | -12.3 |
| B-T magnitude: | 8.718 |
| V-T magnitude: | 8.156 |
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