Gaia Data Release 2: first stellar parameters from Apsis

Understand

The second Gaia data release (Gaia-DR2) contains, beyond the astrometry, three-band photometry for 1.38 billion sources.

• We have used these three broad bands to infer stellar effective temperatures, Teff, for all sources brighter than G=17 mag with Teff in the range 3000-10 000 K (161 million sources).
• Using in addition the parallaxes, we infer the line-of-sight extinction, A_G, and the reddening, E[BP-RP], for 88 million sources.
• Together with a bolometric correction we derive luminosity and radius for 77 million sources.