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gaia data release 3 documentation

14.1 Introduction

14.1.4 Photometry

Photometry in Gaia DR3 is identical to the one in Gaia EDR3 except for a small (order 0.01 mag) colour-dependent correction to G magnitudes for 2p and 6p solutions.

  • The comparison of Gaia DR3 photometry to external catalogues shows that issues are mainly seen in the bright end, i.e. brighter than 5-6 mag, and in GRP for GRP fainter than 18 mag.

  • Comparison with GOG simulations (Section 14.3) shows that at high latitudes the values of GBP-GRP for GOG20 and Gaia EDR3 are in good agreement, but not at bright magnitudes where the colour determination seems to be problematic; however, this discrepancy is slightly reduced compared to Gaia DR2.

  • Results of comparison with CALSPEC are globally better than for Gaia DR2 except for GRP, which does not go through zero and confirms the magnitude dependence seen in the Hipparcos comparison. This is inside the expected uncertainties of the libraries and is not considered problematic.

  • The pattern of the ecliptic that was present in Gaia DR2 for sky maps of sources with phot_bp_rp_excess_factor lower than 5 is no longer visible, meaning that the background due to zodiacal light has been successfully removed.

  • The phot_bp_rp_excess_factor values are improved with respect to Gaia DR2 mainly for faint sources

  • Median differences between Gaia DR2 and Gaia EDR3 photometry in open clusters are very small (Section 14.7), i.e. -0.0087 (G), 0.0027 (GBP), 0.0074 (GRP), 0.0074 (GBP-GRP), with dispersions of the order of 0.01-0.02 in G, GBP, GBP-GRP and lower in GRP. However, for a small sample of stars differences can be higher than 1.5-1.7 mag in GBP and G, possibly related to the small number of observations (<30).

  • Photometry in crowded fields (globular clusters, Section 14.7) is still worse than in non crowded regions, with deviations both in colour and in magnitude already present at phot_bp_rp_excess_factor >2.