3D hydrodynamical simulations of stellar photospheres with the CO5BOLD code: photometric colors of a late-type giant

Abstract

We present synthetic broad-band photometric colors of a late-type giant located close to the RGB tip (T_eff = 3640 K, log g = 1.0 and [M/H] = 0.0). Johnson-Cousins-Glass BVRIJHK colors were obtained from the spectral energy distributions calculated using 3D hydrodynamical and 1D classical stellar atmosphere models. The differences between photometric magnitudes and colors predicted by the two types of models are significant, especially at optical wavelengths where they may reach, e.g., ΔV~0.16, ΔR~0.13 and Δ(V-I)~0.14, Δ(V-K)~0.20. Differences in the near-infrared are smaller but still non-negligible (e.g., ΔK~0.04). Such discrepancies may lead to noticeably different photometric parameters when these are inferred from photometry (e.g., effective temperature will change by ΔT_eff~60 K due to difference of Δ(V-K)~0.20).

Paper presented at IAU General Assembly Joint Discussion 10 "3D Views on Cool Stellar Atmospheres: Theory Meets Observation"; to appear in a dedicated volume of the "Memorie della Societa Astronomica Italiana"; 4 pages, 2 figures; reference added