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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.
| Interstellar polarization at high galactic latitudes from distant stars. V. First results for the South Galactic Pole
We present the first results of our interstellar polarization programmefor the South Galactic Pole (b<-70degr ). The new observations (43stars) combined with previously published data show that there is asubstantial interstellar polarization in this area of the sky. Startingat a distance of 300 pc, we have found stars with P > 0.3% includingone for which P ~ 0.6%. These measurements lead to the conclusion thatthere is a significant amount of interstellar dust at high southgalactic latitudes. Futhermore, there is a remarkable alignment seenover the South Polar Cap: for most stars the directions of polarizationvectors are aligned with the longitude l ~ 80degr , close to theexpected direction of the global magnetic field. In this respect the SGPseems to differ strongly from its northern counterpart.
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Osservazione e dati astrometrici
| Costellazione: | Balena |
| Ascensione retta: | 00h45m43.47s |
| Declinazione: | -21°13'00.8" |
| Magnitudine apparente: | 9.807 |
| Moto proprio RA: | -14.7 |
| Moto proprio Dec: | 3.8 |
| B-T magnitude: | 10.286 |
| V-T magnitude: | 9.847 |
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