The UBV(RI)c colors of the Sun

TL;DR

This study precisely measures the UBV(RI)c colors of the Sun using both model-dependent and independent methods, based on a sample of solar analogs and twins, providing key reference data for solar and stellar studies.

Contribution

It provides the most precise solar colors in the UBV(RI)c system using a large sample of solar analogs and twins, employing both spectroscopic and spectral line-depth ratio methods.

Findings

Derived solar colors with ~0.01 mag precision.

Consistent results from model-dependent and independent methods.

Solar colors: (B-V)=0.653, (U-B)=0.158, (V-R)=0.356, (V-I)=0.701.

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 ~0.01 mag 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 ten 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 1 sigma 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.