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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.
| The DDO IVC Distance Project: Survey Description and the Distance to G139.6+47.6
We present a detailed analysis of the distance determination for oneintermediate-velocity cloud (IVC, G139.6+47.6) from the ongoing DDO IVCDistance Project. Stars along the line of sight to G139.6+47.6 areexamined for the presence of sodium absorption attributable to thecloud, and the distance bracket is established by astrometric andspectroscopic parallax measurements of demonstrated foreground andbackground stars. We detail our strategy regarding target selection,observational setup, and analysis of the data, including a discussion ofwavelength calibration and sky subtraction uncertainties. We find adistance estimate of 129+/-10 pc for the lower limit and257+211-33 pc for the upper limit. Given the highnumber of stars showing absorption due to this IVC, we also discuss thesmall-scale covering factor of the cloud and the likely significance ofnondetections for subsequent observations of this and other similarIVCs. Distance measurements of the remaining targets in the DDO IVCproject will be detailed in a companion paper.
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Посматрања и Астрометриски подаци
| Сазвежђа: | Велики медвед |
| Ректацензија: | 11h09m53.77s |
| Deклинација: | +66°45'24.5" |
| Apparent магнитуда: | 8.11 |
| Даљина: | 244.499 parsecs |
| Proper motion RA: | 13.7 |
| Proper motion Dec: | -10.8 |
| B-T magnitude: | 8.448 |
| V-T magnitude: | 8.138 |
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