Regression of stellar effective temperatures in GaiaDR2

I/345), based on the combination of the stars in four spectroscopic surveys: the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, Sloan Extension for Galactic Understanding and Exploration, the Apache Point Observatory Galactic Evolution Experiment, and the Radial Velocity Extension.

This combination, of about four million stars, enables us to construct one of the largest training samples for the regression and further predict reliable stellar temperatures with a rms error of 191 K. This result is more precise than that given by the Gaia second data release that is based on about sixty thousands stars. After a series of data cleaning processes, the input features that feed the regressor are carefully selected from the Gaia parameters, including the colors, the 3D position, and the proper motion.