# 7.1 Introduction

Author(s): Laurent Eyer

This chapter presents the models and methods used on the Gaia 22 months data to produce the Gaia variable star results for Gaia DR2. The variability processing and analysis was based mostly on the calibrated $G$, and integrated $G_{\rm BP}$ and $G_{\rm RP}$ photometry.

The variability analysis approach to the Gaia data was described in Eyer et al. (2017), and the Gaia DR2 results are presented in Holl et al. (2018). Detailed methods on specific topics will be published in a number of separate articles, after the data release date. Variability behaviours in colour magnitude diagrams will be presented in Gaia Collaboration et al. (2018c).

This Chapter 7 is organised as follows: the global processing is described in Section 7.2 and subsequent Sections present different data products: the whole sky classification in Section 7.3, RR Lyrae star and Cepheid candidates in Section 7.4, BY Draconis candidates in Section 7.5, short time scale variability in Section 7.6, and long period variable stars in Section 7.7.