Correction to the photometric colors of Gaia Early Data Release 3

TL;DR

This paper presents precise color corrections for Gaia EDR3 using a large spectroscopic dataset, improving calibration accuracy and addressing systematic trends in stellar photometry.

Contribution

It introduces a new spectroscopic regression method to refine Gaia EDR3 color calibrations, reducing systematic errors and providing correction terms for a wide magnitude range.

Findings

Color term in GBP - GRP removed after calibration

Systematic trends with G magnitude identified

Correction functions provided for 9.5 < G < 17.5 mag

Abstract

In this work, we use the spectroscopy-based stellar color regression (SCR) method with ~ 0.7 million common stars between LAMOST DR7 and Gaia EDR3 to acquire color corrections in G - GRP and GBP - GRP. A sub-mmag precision is achieved. Our results demonstrate that improvements in the calibration process of the EDR3 have removed the color term in GBP - GRP and eliminated the discontinuity caused by the changes of instrument configurations to a great extent. However, modest systematic trends with G magnitude are still detected. The corresponding color correction terms as a function of G are provided for 9.5 < G < 17.5 mag and compared with other determinations. We conclude that the corrections given in this work are particularly suited for cases where the color-color investigations are required while for color-magnitude investigations other corrections may be better due to systematic with reddening. Possible applications of our results are discussed.