F. X. Pineau

TL;DR: Gaia as discussed by the authors is a cornerstone mission in the science programme of the European Space Agency (ESA). The spacecraft construction was approved in 2006, following a study in which the original interferometric concept was changed to a direct-imaging approach.

TL;DR: In this paper, the authors describe the processing of the Gaia DR2 data, and describe the criteria used to select the sample published in Gaia DR 2, and explore the data set to assess its quality.

TL;DR: In this paper, the second data release of the Gaia mission and its power for constraining many different aspects of the dynamics of the satellites of the Milky Way is demonstrated. But the accuracy of the errors, statistical and systematic, are relatively well understood.

TL;DR: The 4XMM-DR9 catalog as discussed by the authors contains 810795 detections down to a detection significance of 3σ, of which 550124 are unique sources, which cover 1152 degrees$^{2}$ (2.85%) of the sky.

TL;DR: The 4XMM-DR9 catalog as mentioned in this paper contains 810795 detections down to a detection significance of 3σ, of which 550124 are unique sources, which cover 1152 degrees$^{2}$ (2.85%) of the sky.