Gaia DR3 G-band bolometric correction

Bolometric corrections in the Gaia (E)DR3 G-band, BC_G, were evaluated on a grid of MARCS models (Gustafsson et al. 2008) supplemented with intermediate temperature stars (Shulyak et al. 2004). They were used to produce the luminosities (lum_flame, lum_flame_spec) from the FLAME module which are published in the Gaia DR3 astrophysical_parameters and astrophysical_parameters_supp tables (Creevey et al. 2022). The BC_G is given as an auxiliary parameter in these tables (bc_flame, bc_flame_spec). The parameters lum_flame and bc_flame are found in the astrophysical_parameters table for ~280 million sources in Gaia DR3 and are based on the atmospheric properties from the GSP-Phot module which analyses BP/RP spectra (Andrae et al. 2022), while lum_flame_spec and bc_flame_spec are found in the astrophysical_parameters_supp table for ~5 million sources and based on the atmospheric properties from the GSP-Spec module which analyses RVS spectra (Recio-Blanco et al. 2022).

We provide this bolometric correction function to the user which is based on the same set of models and interpolation method that was used in Gaia DR3.

The source code in python and instructions for use can be found here: https://gitlab.oca.eu/ordenovic/gaiadr3_bcg.

The function takes as input the effective temperature T_eff , surface gravity log g, iron abundance [Fe/H], and alpha-enhancement [alpha/Fe], and returns the model BC_G value for that combination of parameters. The value of BC_G is based on the assumption of M_G,Sun = 4.66 mag, i.e. BC_G,Sun = +0.08 mag, see Creevey et al. (2022) for details. A user can specify an offset (in magnitudes) to this reference zeropoint directly in the function.

The function is valid in the T_eff range of 2,500 – 20,000 K, log g between –0.5 and +5.0, [Fe/H] from –5.0 to +1.5 and [alpha/Fe] from +0.0 to +0.4.

References:

• Gustafsson, B., Edvardsson, B., Eriksson, K, et al. 2008, A&A, 486, 951
• Riello M., De Angeli F., Evans D.W., et al., Dec. 2020, A&A, 649, A3
• Shulyak, Valyavin, G., Khan, S. et al. 2004, A&A, 428, 993
• Creevey, O. L., Sordo, R., Pailler F., et al. 2022, A&A, "Gaia Data Release 3: Astrophysical parameters inference system (Apsis) I - overview"
• Andrae et al. 2022, A&A, "Gaia Data Release 3: General Stellar Parametrizer from Photometry"
• Recio-Blanco et al. 2022, A&A, "Gaia Data Release 3: Analysis of the Gaia RVS spectra by the General Stellar Parameterizer-Spectroscopy module"

Acknowledgements:

When using this function we ask you to cite Creevey, O. L., Sordo, R., Pailler F., et al. 2022, A&A, "Gaia Data Release 3: Astrophysical parameters inference system (Apsis) I - overview"

This product makes use of public auxiliary models provided by ESA/Gaia/DPAC/CU8 and prepared by Christophe Ordenovic, Orlagh Creevey, Andreas Korn, Bengt Edvardsson, Oleg Kochukhov, and
Frédéric Thévenin.