THE UBV(RI) C colors of the sun

Abstract

Photometric data in the UBV(RI)C system have been acquired for 80 solar analog stars for which we have previously derived highly precise atmospheric parameters Teff, log g, and [Fe/H] using high-resolution, high signal-to-noise ratio spectra. UBV and (RI)C data for 46 and 76 of these stars, respectively, are published for the first time. Combining our data with those from the literature, colors in the UBV(RI)C system, with ≃ 0.01mag precision, are now available for 112 solar analogs. Multiple linear regression is used to derive the solar colors from these photometric data and the spectroscopically derived Teff, log g, and [Fe/H] values. To minimize the impact of systematic errors in the model-dependent atmospheric parameters, we use only the data for the 10 stars that most closely resemble our Sun, i.e., the solar twins, and derive the following solar colors: (B - V) = 0.653 ± 0.005, (U - B) = 0.166 ± 0.022, (V - R) = 0.352 ± 0.007, and (V - I) = 0.702 ± 0.010. These colors are consistent, within the 1σ errors, with those derived using the entire sample of 112 solar analogs. We also derive the solar colors using the relation between spectral-line-depth ratios and observed stellar colors, i.e., with a completely model-independent approach, and without restricting the analysis to solar twins. We find (B - V) = 0.653 ± 0.003, (U - B) = 0.158 ± 0.009, (V - R) = 0.356 ± 0.003, and (V - I) = 0.701 ± 0.003, in excellent agreement with the model-dependent analysis.