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Metallicities and activities of southern stars
Aims. We present the results from high-resolution spectroscopicmeasurements to determine metallicities and activities of bright starsin the southern hemisphere. Methods: We measured the iron abundances([Fe/H]'s) and chromospheric emission indices (log h{R}'{HK})of 353 solar-type stars with V = 7.5-9.5. [Fe/H] abundances aredetermined using a custom χ2 fitting procedure within alarge grid of Kurucz model atmospheres. The chromospheric activitieswere determined by measuring the amount of emission in the cores of thestrong Caii HK lines. Results: Our comparison of the metallicity sampleto other [Fe/H] determinations was found to agree at the ±0.05dex level for spectroscopic values and at the ±0.1 dex level forphotometric values. The distribution of chromospheric activities isdescribed by a bimodal distribution, agreeing with the conclusions fromother works. Also an analysis of Maunder minimum status was attempted,and it was found that 6 ± 4 stars in the sample could be in aMaunder minimum phase of their evolution and hence the Sun should onlyspend a few per cent of its main sequence lifetime in Maunder minimum.Based on observations made with the ESO telescopes at the La SillaParanal observatory under programme ID's 076.C-0578(B) and077.C-0192(A). Table 4 is 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/485/571
| Search for pulsation among suspected A-type binaries and the new multiperiodic δ Scuti star HD 217860
Context: In the H-R diagram, the intersection of the main sequence andthe classical Cepheid instability strip corresponds to a domain where arich variety of atmospheric phenomena are at play (including pulsation,radiative diffusion, convection). Main-sequence A-type stars are amongthe best candidates to study the complex interplay between these variousphenomena. Aims: We have explored a sample of suspected A-type binariesin a systematic way, both spectroscopically and photometrically. Thesample consists of main-sequence A-type stars for which the few existingradial velocity measurements may show variability, but for which otheressential information is lacking. Due to their location in the H-Rdiagram, indications of pulsation and/or chemical peculiarities amongthese suspected binary (or multiple) systems may be found. Methods:High-resolution spectroscopy obtained with the ELODIE and MUSICOSspectrographs was used in combination with a few nights of differentialCCD photometry in order to search for pulsation(s). In order to searchas well for chemical peculiarities or for possible hidden component(s),we derived the atmospheric stellar parameters by fitting the observedspectra with LTE synthetic ones. Results: Of the 32 investigatedtargets, eight are spectroscopic binaries, one of which is a closebinary also showing eclipses, and three have been identified as δScuti pulsators with rapid line-profile variations. Conclusions: Amongthe latter stars, HD 217860 reveals interesting multiperiodicphotometric and spectroscopic variations, with up to eight frequenciescommon to two large photometric data sets. We suggest that at least oneradial overtone mode is excited among the two most dominant frequencies,on the basis of the computation of the pulsation constants as well as ofthe predicted frequencies and the expected behaviour of the amplituderatio and the phase difference in two passbands using adequatetheoretical modelling. We furthermore found evidence for a strongmodulation of the amplitude(s) and/or the (radial) frequency content ofthis intriguing δ Scuti star.This work is based on spectroscopic observations made at theHaute-Provence Observatory (OHP), the Observatoire du Pic du Midi (TBL)and the Bulgarian National Astronomical Observatory (NAO, Rozhen).Tables 1, 2, 4, 5 and Fig. 7 are only available in electronic form athttp://www.aanda.org
| 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.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| 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
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| קבוצת-כוכבים: | שעון |
| התרוממות ימנית: | 03h32m01.85s |
| סירוב: | -52°28'25.9" |
| גודל גלוי: | 7.777 |
| מרחק: | 50.813 פארסק |
| תנועה נכונה: | 162.4 |
| תנועה נכונה: | -61 |
| B-T magnitude: | 8.672 |
| V-T magnitude: | 7.851 |
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