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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
| HIPPARCOS age-metallicity relation of the solar neighbourhood disc stars
We derive age-metallicity relations (AMRs) and orbital parameters forthe 1658 solar neighbourhood stars to which accurate distances aremeasured by the HIPPARCOS satellite. The sample stars comprise 1382 thindisc stars, 229 thick disc stars, and 47 halo stars according to theirorbital parameters. We find a considerable scatter for thin disc AMRalong the one-zone Galactic chemical evolution (GCE) model. Orbits andmetallicities of thin disc stars show now clear relation each other. Thescatter along the AMR exists even if the stars with the same orbits areselected. We examine simple extension of one-zone GCE models whichaccount for inhomogeneity in the effective yield and inhomogeneous starformation rate in the Galaxy. Both extensions of the one-zone GCE modelcannot account for the scatter in age - [Fe/H] - [Ca/Fe] relationsimultaneously. We conclude, therefore, that the scatter along the thindisc AMR is an essential feature in the formation and evolution of theGalaxy. The AMR for thick disc stars shows that the star formationterminated 8 Gyr ago in the thick disc. As already reported by Grattonet al. (\cite{Gratton_et.al.2000}) and Prochaska et al.(\cite{Prochaska_et.al.2000}), thick disc stars are more Ca-rich thanthin disc stars with the same [Fe/H]. We find that thick disc stars showa vertical abundance gradient. These three facts, the AMR, verticalgradient, and [Ca/Fe]-[Fe/H] relation, support monolithic collapseand/or accretion of satellite dwarf galaxies as likely thick discformation scenarios. Tables 2 and 3 are only available in electronicform at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)or via http:/ /cdsweb.u-strasbg.fr/ cgi-bin/qcat?J/ A+A/394/927
| Pulsation in lambda Bootis stars
In this paper we present a further step in applying asteroseismictechniques to the group of lambda Bootis stars which can becharacterized as nonmagnetic A to F-type Population I dwarfs withsignificant (surface) underabundances of Fe-peak elements. Since noconclusive theory explaining the origin of the observed abundanceanomalies exists, an extensive photometric survey for pulsation in thisgroup has been initiated. Knowledge about the pulsational properties(most members are located within the classical instability strip) couldhelp to establish constrains about the overall abundance of these starsas well as on the evolutionary status. New photometric observations werecarried out for eleven stars. Variability was detected in four stars(e.g. lambda Bootis itself) whereas the remaining seven objects areprobably constant. In total, 52 members of this group have beenphotometrically investigated so far. With 22 pulsating and 30``constant'' stars, we derive a ratio of at least 50 % for variable tononvariable members inside the classical instability strip. This resultis based on high quality Hipparcos and new photometric data. Theobserved log /lineρ//lineρ_ȯ and log P values for thepulsating members are compatible with standard (solar abundant) deltaScuti models supporting the hypothesis that the found abundanceanomalies are restricted to the surface only. Otherwise the pulsationalproperties of this group are not outstanding compared to ``normal''delta Scuti stars, indicating that the mechanism driving the pulsationsis very similar. Based on observations obtained at ESO-La\,Silla, CTIO,SAAO, McDonald Observatory, Instituto Astrofisica Andalucia Observatoryand with the Hipparcos satellite
| 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
| Kinematics and properties of F stars near the North Galactic Pole. II - The isothermal disc
Radial velocities are given for about 550 photometrically-identifieddisk-population F stars lying within 15 deg of the North Galactic Pole.The overall radial and z-velocity distributions are found to be closelyGaussian, with corrected rms and mean z velocities of 11.3 + or - 0.6and -9.5 + or - 0.5 km/s, respectively. The isothermal kinematics of thepopulation are reflected in the constant velocity dispersion to a zdistance of 400 pc. No systematic variation of either the velocitydispersion or the stellar age with the metallicity-sensitive Stromgrendelta m1 index is noted over a range of ages up to 5 Gyr.
| Further Studies of A-Stars and F-Stars in the Region of the North Galactic Pole - Part Four - a Catalogue of Uvbyr Photometry and Derived Quantities
Not Available
| Further Studies of A-Stars and F-Stars in the Region of the North Galactic Pole - Part Three - a Catalogue of Star Names and Positions
Not Available
| Studies of A and F stars in the region of the North galactic pole-II. uvby β photometry
Not Available
| Studies of A and F stars in the region of the North galactic pole-I. Radial velocities and MK Classifications
Not Available
| Narrow-band photometry of late-type stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970A&AS....1..199H&db_key=AST
| Space distribution of stars of intermediate spectral type in a North galactic pole region.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1963AJ.....68..194U&db_key=AST
| Investigations on the stars in high galactic latitudes. III. Spectrophotometric analysis of about 3000 stars down to the photographic magnitude 13.5.
Not Available
| Stars with large proper motions in the astrographic zones+ 32° and + 33° (List I)
Not Available
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Observation and Astrometry data
| Constellation: | Coma Berenices |
| Right ascension: | 12h12m51.94s |
| Declination: | +31°47'46.1" |
| Apparent magnitude: | 7.762 |
| Distance: | 73.099 parsecs |
| Proper motion RA: | 22.3 |
| Proper motion Dec: | -39 |
| B-T magnitude: | 8.396 |
| V-T magnitude: | 7.815 |
Catalogs and designations:
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INHABITED SKY
