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

TL;DR

This study compares 3D hydrodynamical and 1D classical stellar atmosphere models to predict photometric colors of a late-type giant, revealing significant differences especially in optical wavelengths that impact stellar parameter estimations.

Contribution

It provides the first detailed comparison of photometric colors from 3D hydrodynamical and 1D models for a late-type giant, highlighting the importance of 3D effects.

Findings

Significant differences in optical colors between models, up to 0.16 mag in V.

Near-infrared differences are smaller but still relevant, around 0.04 mag in K.

Photometric parameter estimates, like effective temperature, can vary by about 60 K due to model differences.

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., \Delta V~0.16, \Delta R~0.13 and \Delta (V-I)~0.14, \Delta (V-K)~0.20. Differences in the near-infrared are smaller but still non-negligible (e.g., \Delta K~0.04). Such discrepancies may lead to noticeably different photometric parameters when these are inferred from photometry (e.g., effective temperature will change by \Delta T_eff~60 K due to difference of \Delta (V-K)~0.20).