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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.
| Fundamental properties of the open cluster NGC 2355
NGC 2355 is an old open cluster in the outer part of the galactic disk(l=203fdg4 , b=+11fdg8 ) which has been little studied until now. Thispaper presents the first astrometric and spectroscopic investigation ofthis cluster. We have measured precise absolute proper motions from oldCarte du Ciel plates, POSS-I plates and recent CCD observations obtainedwith the Bordeaux meridian circle. The proper motion data reveal 38highly probable cluster members down to Blim = 15 mag within7' of the cluster center. We have also obtained ELODIE high resolutionspectra for 24 stars. Seventeen of them are confirmed to be members ofthe cluster on the basis of radial velocity. Eight of them are fastrotating turnoff stars for which the projected rotational velocity hasbeen determined. The spectroscopic observations have also providedestimates of the physical parameters Teff, log g, {[Fe/H]},MV of the 24 target stars. Two stragglers have beenidentified in the cluster. Combining our astrometric and spectroscopicresults with previous UBV photometry and recent JHK_s photometry fromthe 2MASS survey we have derived the fundamental properties of thecluster: metallicity, age, distance, size, spatial velocity and orbit.Based on observations made on the 193cm telescope at the Haute-ProvenceObservatory, France, and on plate digitisation at the Centre d'Analysedes Images, Paris. This publication makes use of data products from theTwo Micron All Sky Survey, which is a joint project of the University ofMassachusetts and the Infrared Processing and Analysis Center, funded bythe National Aeronautics and Space Administration and the NationalScience Foundation.
| 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 Kreinin-Murri Method for Absolute Determination of Equatorial-Star Declinations.
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Pozíciós és asztrometriai adatok
| Csillagkép: | Vízöntő |
| Rektaszcenzió: | 20h20m57.31s |
| Deklináció: | +00°05'38.5" |
| Vizuális fényesség: | 8.676 |
| Távolság: | 268.097 parszek |
| RA sajátmozgás: | 18.4 |
| Dec sajátmozgás: | -4.5 |
| B-T magnitude: | 9.091 |
| V-T magnitude: | 8.711 |
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