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Preliminary UVBY calibrations for G and K type dwarf stars Four-color uvby photometry for several hundred late-type dwarf stars oftypes G, K and M is discussed. Mean values of photometric indices aregiven for MK spectral types between F8/G0V and M2V. Preliminary standardrelations between the four-color indices are derived. Based onparallaxes and results from high-dispersion spectroscopic analyses,calibrations of the observed indices in terms of Mv, log Te and Fe/Hhave been derived. The means errors are 0.29 mag, 0.009 dex, and 0.17dex, respectively. The calibrations are valid for class-V stars of allpopulations between G0 and M2. If extreme population-II dwarfs areexcluded, the mean error of the abundance calibration decreases to 0.13dex. Calibrations in terms of log g have been attempted,, but the lowaccuracy of the spectroscopic g determinations does not inspireconfidence in the results. The possible contribution of a'fourth-parameter' variation to the mean errors of the calibrations isbriefly discussed. This fourth parameter could be the intrinsic heliumabundance of the stars.
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Группы:
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Наблюдательные данные и астрометрия
Созвездие: | Тукан |
Прямое восхождение: | 22h50m54.52s |
Склонение: | -62°48'52.9" |
Видимая звёздная величина: | 7.594 |
Расстояние: | 83.333 парсек |
Собственное движение RA: | -18.8 |
Собственное движение Dec: | -1.9 |
B-T magnitude: | 8.493 |
V-T magnitude: | 7.669 |
Каталоги и обозначения:
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