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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
| Radial velocities. Measurements of 2800 B2-F5 stars for HIPPARCOS
Radial velocities have been determined for a sample of 2930 B2-F5 stars,95% observed by the Hipparcos satellite in the north hemisphere and 80%without reliable radial velocity up to now. Observations were obtainedat the Observatoire de Haute Provence with a dispersion of 80Ä,mm(-1) with the aim of studying stellar and galactic dynamics.Radial velocities have been measured by correlation with templates ofthe same spectral class. The mean obtained precision is 3.0 km s(-1)with three observations. A new MK spectral classification is estimatedfor all stars. Based on observations made at the Haute ProvenceObservatory, France and on data from The Hipparcos Catalogue, ESA.Tables 4, 5 and 6 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr or viahttp://cdsweb.u-strasbg.fr/Abstract.htm
| Stroemgren photometry of F- and G-type stars brighter than V = 9.6. I. UVBY photometry
Within the framework of a large photometric observing program, designedto investigate the Galaxy's structure and evolution, Hβ photometryis being made for about 9000 stars. As a by-product, supplementary uvbyphotometry has been made. The results are presented in a cataloguecontaining 6924 uvby observations of 6190 stars, all south ofδ=+38deg. The overall internal rms errors of one observation(transformed to the standard system) of a program star in the interval6.5
| The absolute magnitudes of RR Lyrae stars. I - X ARIETIS
A Baade-Wesselink analysis based on the infrared flux method ofBlackwell and Shallis (1977) is used to estimate the temperature andangular diameter of X Ari at all phases of the pulsational cycle. Theseresults are then used to determine the radius, distance, and absolutemagnitude. New UV, optical and IR observations for this metal-poor starare also presented. The present results are compared with those ofManduca et al. (1981).
| The Baade-Wesselink method and the distances to RR Lyrae stars. II - The field star X ARIETIS
VR and JHK photometry and radial velocities with typical accuracies of 1km/sec for the metal-poor RR Lyrae field star X Arietis. These data,along with unpublished UVBY photometry, have been used to derive thedistance to X Ari using two variations of the Baade-Wesselink method.The possibility of photospheric velocity gradients that might distortthe value of the systemic velocity and cause a phase shift was examined,and it was found that no gradient exists in the part of the stellaratmosphere considered. The phasing problem previously noted for VY Serby Carney and Latham (1984) also occurs for X Ari when opticalphotometry is used to compute the effective temperatures, but not whenthe V - K color index is used. Possible causes of these phase shifts arediscussed, and it is concluded that X Ari has an aggregate average Vmagnitude of 0.73-1.03 mag on the basis of the V - K results.
| The visual surface brightness relation and the absolute magnitudes of RR Lyrae stars. II - RR Lyrae and X ARIETIS
The theoretical surface brightness relation for RR Lyrae stars has beencombined with new VR photometry to determine distances, radii, andabsolute magnitudes for X Arietis and RR Lyrae. For X Arietis, apulsational variation in the radius from 5.06 solar radii to 5.96 solarradii, a distance of 495 + or - 50 pc, and an intensity mean absolutemagnitude of +0.59 + or - 0.25 is obtained. The corresponding quantitiesfor RR Lyrae are 4.81-5.67 solar radii, 263 + or - 39 pc, and anintensity mean absolute magnitude of +0.61 + or - 0.35. The largererrors quoted for RR Lyrae are due to uncertainties arising from theBlazhko effect. Results are discussed in the context of the dependenceof RR Lyrae absolute magnitudes on metal abundance.
| Erratum : MK classification for F- and G-type stars. II.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970AJ.....75..507H&db_key=AST
| MK classifications for F-and G-type stars. II.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970AJ.....75..165H&db_key=AST
| Identifications of Comparison Stars for RR Lyrae Variables
Not Available
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Besorolás csoportokba:
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Pozíciós és asztrometriai adatok
| Csillagkép: | Kos |
| Rektaszcenzió: | 03h08m25.16s |
| Deklináció: | +10°47'45.2" |
| Vizuális fényesség: | 7.31 |
| Távolság: | 123.305 parszek |
| RA sajátmozgás: | -63.4 |
| Dec sajátmozgás: | -31.2 |
| B-T magnitude: | 7.798 |
| V-T magnitude: | 7.351 |
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