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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.
| Preparing the COROT Space Mission: New Variable Stars in the Galactic Anticenter Direction
The activities related to the preparation of the asteroseismic,photometric space mission COROT are described. Photoelectricobservations, wide-field CCD photometry, uvbyβ calibrations, andfurther time series have been obtained at different observatories andtelescopes. They have been planned to complete the COROT program in thedirection of the Galactic anticenter. In addition to suitableasteroseismic targets covering the different evolutionary stages betweenzero-age main sequence and terminal-age main sequence, we discoveredseveral other variable stars, both pulsating and geometric. We comparedresults on the incidence of variability in the Galactic center andanticenter directions. Physical parameters have been obtained, andevolutionary tracks fitting them have been calculated. The peculiaritiesof some individual stars are pointed out.Based on observations collected at the San Pedro Martír, SierraNevada, Teide, La Silla, Haute-Provence, and Roque de Los Muchachos(Telescopio Nazionale Galileo and Mercator telescopes) observatories.
| Multi-site, multi-technique survey of γ Doradus candidates. I. Spectroscopic results for 59 stars
We present the first results of a 2-year high-resolution spectroscopycampaign of 59 candidate γ Doradus stars which were mainlydiscovered from the HIPPARCOS astrometric mission. More than 60% of thestars present line profile variations which can be interpreted as due topulsation related to γ Doradus stars. For all stars we alsoderived the projected rotation velocity (up to more than 200 kms-1). The amplitude ratios 2K/Δ m for the mainHIPPARCOS frequency are in the range 35-96 kms-1,mag-1. About 50% of the candidates arepossible members of binary systems, with 20 stars being confirmedγ Doradus. At least 6 stars present composite spectra, and in allbut one case (for which only one spectrum could be obtained), the narrowcomponent shows line profile variations, pointing towards anuncomfortable situation if this narrow component originates from a shellsurrounding the star. This paper is the first of a series concerningmode identification using both photometric and spectroscopic methods forthe confirmed γ Doradus stars of the present sample.Partially based on observations obtained at the Observatoire deHaute-Provence.
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Osservazione e dati astrometrici
| Costellazione: | Orione |
| Ascensione retta: | 06h20m42.74s |
| Declinazione: | +05°16'42.1" |
| Magnitudine apparente: | 7.552 |
| Distanza: | 92.764 parsec |
| Moto proprio RA: | -25.4 |
| Moto proprio Dec: | -30.1 |
| B-T magnitude: | 7.9 |
| V-T magnitude: | 7.581 |
Cataloghi e designazioni:
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