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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.
| Narrow-band photometry of the long-period variables.
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| Interstellar extinction and polarimetric properties of the star HD 200775
Reddening and polarization are obtained and separated into intrinsic andinterstellar components for the Herbig Be star HD 200775, which issurrounded by the NGC 7023 reflection nebula. A reddening map based onstar counts is used to derive the relation between (C-13)O columndensity and extinction, and the maximum interstellar polarization isfound to be 0.88 percent at the maximum wavelength of 0.532 microns;this indicates that the size distribution of the particles in the cloudresponsible for the optical extinction and polarization is rathersimilar to that of the surrounding interstellar medium.
| B V Observations of Six Red Variable Stars
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Osservazione e dati astrometrici
| Costellazione: | Cefeo |
| Ascensione retta: | 21h07m16.41s |
| Declinazione: | +68°36'54.9" |
| Magnitudine apparente: | 8.094 |
| Distanza: | 138.504 parsec |
| Moto proprio RA: | -17.9 |
| Moto proprio Dec: | -14.9 |
| B-T magnitude: | 8.464 |
| V-T magnitude: | 8.125 |
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