Correction to the photometric colors of the Gaia Data Release 2 with the stellar color regression method

TL;DR

This paper improves Gaia DR2 photometric data by applying a stellar color regression method, correcting systematic effects to enhance the data's precision for scientific use.

Contribution

It introduces a spectroscopy-based calibration method that significantly reduces systematic errors in Gaia DR2 photometry, revealing detailed magnitude-dependent trends.

Findings

Systematic trends with G magnitude are identified and corrected.

Calibration improves photometric precision to about 1 mmag.

Revised Gaia DR2 color-color diagram provided.

Abstract

The second Gaia data release (DR2) delivers accurate and homogeneous photometry data of the whole sky to an exquisite quality, reaching down to the unprecedented milli-magnitude (mmag) level for the G, GRP, and GBP passbands. However, the presence of magnitude-dependent systematic effects at the 10 mmag level limits its power in scientific exploitation. In this work, using about half-million stars in common with the LAMOST DR5, we apply the spectroscopy-based stellar color regression method to calibrate the Gaia G-GRP and GBP-GRP colors. With an unprecedented precision of about 1 mmag, systematic trends with G magnitude are revealed for both colors in great detail, reflecting changes in instrument configurations. Color dependent trends are found for the GBP-GRP color and for stars brighter than G~11.5 mag. The calibration is up to 20 mmag in general and varies a few mmag/mag. A revised color-color diagram of Gaia DR2 is given, and some applications are briefly discussed.