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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.
| Stellar uvbybeta photometry in three EUV shadow directions
We present the uvbybeta data used to locate the dust and derivedistances for nearby diffuse interstellar clouds in the EUV shadowslb27-31, lb165-32 and lb329+46 discovered by the Extreme UltravioletExplorer. The photometrically derived parallaxes of our program starsare compared to the parallaxes listed in the Hipparcos Catalog. Withinthe photometric distance limit of 150 pc, the photometric parallaxes of21 ``normal" stars are consistent with the Hipparcos measurements withinan uncertainty of 15%. Much as expected for the Str{ömgren system.Since all program stars are brighter than V~11.5 most of them areincluded in the Tycho photometry. For our sample of ~ 200 stars we findVby and V_T to be consistent. Few stars are common topublished uvbybeta catalogs, ~ 10, V and the indices compare well apartfrom beta where a zero point difference of 11 mmag is noticed.Tables \ref{tab1}-\ref{tab3} are also available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.htmlBased on observations at the European Southern Observatory, La Silla,Chile.
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | גדי |
| התרוממות ימנית: | 20h39m36.21s |
| סירוב: | -20°05'22.6" |
| גודל גלוי: | 9.667 |
| תנועה נכונה: | 0 |
| תנועה נכונה: | 10.8 |
| B-T magnitude: | 10.038 |
| V-T magnitude: | 9.698 |
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