Although a catalogue of synthetic RGB magnitudes, providing photometric data for a sample of 1346 bright stars, has been recently published, its usefulness is still limited due to the small number of reference stars available, considering that they are distributed throughout the whole celestial sphere, and the fact that they are restricted to Johnson V < 6.6 mag. This work presents synthetic RGB magnitudes for ∼15 million stars brighter than Gaia G = 18 mag, making use of a calibration between the RGB magnitudes of the reference bright star sample and the corresponding high-quality photometric G, GBP, and GRP magnitudes provided by the Gaia EDR3. The calibration has been restricted to stars exhibiting −0.5 < GBP − GRP < 2.0 mag, and aims to predict RGB magnitudes within an error interval of ±0.1 mag. Since the reference bright star sample is dominated by nearby stars with slightly undersolar metallicity, systematic variations in the predictions are expected, as modelled with the help of stellar atmosphere models. These deviations are constrained to the ±0.1-mag interval when applying the calibration only to stars scarcely affected by interstellar extinction and with metallicity compatible with the median value for the bright star sample. The large number of Gaia sources available in each region of the sky should guarantee high-quality RGB photometric calibrations.

中文翻译：

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1500 万颗盖亚星的 RGB 光度校准

尽管最近发布了合成 RGB 星等目录，为 1346 颗明亮恒星的样本提供光度数据，但由于可用的参考恒星数量很少，考虑到它们分布在整个天球上，它的用处仍然有限，以及它们仅限于 Johnson V < 6.6 等 这项工作利用参考亮星样本的 RGB 星等与由盖亚 EDR3。校准仅限于表现出 -0.5 < 的恒星。英镑 - GRP < 2.0 mag，旨在在 ±0.1 mag 的误差区间内预测 RGB 幅度。由于参考亮星样本主要是太阳下金属丰度稍低的附近恒星，因此在恒星大气模型的帮助下，预测会出现系统性变化。当仅将校准应用于几乎不受星际消光影响且金属丰度与亮星样本的中值兼容的恒星时，这些偏差被限制在 ±0.1 等间隔内。天空的每个区域都有大量可用的 Gaia 源应保证高质量的 RGB 光度校准。仅对几乎不受星际消光影响且金属丰度与亮星样本中值兼容的恒星应用校准时的 1 等间隔。天空的每个区域都有大量可用的 Gaia 源应保证高质量的 RGB 光度校准。仅对几乎不受星际消光影响且金属丰度与亮星样本中值兼容的恒星应用校准时的 1 等间隔。天空的每个区域都有大量可用的 Gaia 源应保证高质量的 RGB 光度校准。