Fundamental parameters and intrinsic colors of F,G, and K supergiants and classical cepheids |
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| Authors: | V V Kovtyukh C Soubiran S I Belik M P Yasinskaya F A Chekhonadskikh V Malyuto |
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| Institution: | 1.Astronomical Observatory,Mechnikov Odessa National University,Taras Shevchenko Park, Odessa,Ukraine;2.Observatoire de Bordeaux BP21,Floirac,France;3.Tartu Observatory,T?ravere,Estonia |
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| Abstract: | We used high-resolution echelle spectra with high signal-to-noise ratio to determine with a high degree of accuracy some atmospheric parameters (T eff, log g and Fe/H]) for 68 non-variable supergiants of types F, G, and K and 26 classical Cepheids in 302 pulsation phases. Very accurate effective temperatures, with errors of only 10–30 K, were determined by the line-depth ratio method. We found that the observed intrinsic color indices (B ? V)0 can be related to these parameters: (B ? V)0 = 57.984? 10.3587(log T eff)2 + 1.67572(log T eff)3 ? 3.356 log g+ 0.321 V t + 0.2615Fe/H] + 0.8833log g(log T eff). With this empirical relation, the intrinsic colors of individual supergiants and classical Cepheids of spectral types F0-K0 and of luminosity classes I and II can be estimated with an accuracy as high as 0.05 m , which is comparable to the accuracy of the most elaborate photometric procedures. In view of large distances to supergiants, the method we propose here allows a large-scale mapping of interstellar extinction with an accuracy of 0.1–0.2 m in a quite large region of the Galaxy. |
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